Internet Engineering Task Force Hemant Agrawal Internet Draft GlobeSpan Inc draft-agrawal-sip-h323-interworking-00.txt Radhika R Roy February 23, 2001 AT&T Expires: August 2001 Vipin Palawat Cisco Systems Inc Alan Johnston MCI WorldCom Charles Agboh Global Telesystem Group David Wang Nuera Communications Inc Henning Schulzrinne Kundan Singh Columbia University Joon Maeng VTel Communications SIP-H.323 Interworking Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026 [1]. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This document is a product of the SIP-H.323 Interworking Working Group of the Internet Engineering Task Force (IETF). Comments should be submitted to the mailing list sip-h323@yahoogroups.com.com. Copyright Notice Copyright (c) The Internet Society (2000). All Rights Reserved. Agarwal/Roy/Palawat/Johnston/Agboh/Wang/Schulzrine/Singh/Maeng [Page 1] Internet Draft SIP-H.323 Interworking February 2001 Abstract This document describes the interworking between SIP and H.323 protocols. It defines the the logical entity known as the SIP-H.323 Interworking Function (SIP-H.323 IWF) that will allow the interworking between the SIP (Session Initiation Protocol) and H.323 protocols. This includes the call sequence mapping, message parameter mapping, translation between H.245 and SDP, state machines, and handling of different call procedures. Table of Contents 1. Terminology 2. Introduction 3. Background 4. Scope of the document 5. Definitions 6. Overview of IWF Functionality 7. Interworking Requirements for IWF 8.Mapping Between SIP and H.323 in IWF 8.1. Alias Addresses Mapping 8.1.1. Converting SIP Addresses to H.323 Addresses 8.1.2. Examples for Address Resolution 8.1.3. Converting H.323 Addresses to SIP Addresses 8.2 Message Mapping 8.3 Call Sequence Mapping 8.4 Message Parameters Mapping 8.5 Audio/Video Formats Mapping 9. Basic Message Handling 9.1 SIP-originated Requests Received by IWF 9.2 H.323-originated Requests Received by IWF 9.3 Handling of H.323 Signaling Messages 9.3.1 H.225 9.3.1.1 RAS 9.3.1.2 Q.931 9.3.2 H.245 9.4 Handling of SIP Signaling Messages 10.Interworking Call Scenarios for Different Configurations 11. State Machine Agarwal, et al. [Page 2] Internet Draft SIP-H.323 Interworking February 2001 12. Implementation Requirements 13. Activities Planned for Next Phase 14. Security Considerations 15. Known Issues 16. To Do 17. Conclusion Appendix A: Calculating common subset of capabilities Appendix B: Modification in ASN.1 syntax of H.225 Appendix C: Call Flow Message Details Appendix D: Summary of SIP-H.323 Interworking Requirements References Acknowledgments Authors' Addresses Full Copyright Statement 1 Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [2] and indicate requirement levels for compliant implementations. 2. Introduction The primary objective of SIP-H.323 Interworking function (IWF) is to provide protocol conversion between SIP and H.323 protocols. Both of these protocols use similar formats (e.g. RTP) to transfer media (audio/video/data) over the Packet Network. It is, therefore, required to perform the mapping between SIP and H.323 signaling messages only toachieve the interworking between the two protocols. The objective is to transmit media end-to-end directly between the two end systems in H.323 and SIP networks. However, some of the special scenarios may require media to be routed through the IWF using MSF. Such scenarios are out of the scope of the current document. Agarwal, et al. [Page 3] Internet Draft SIP-H.323 Interworking February 2001 The logical relationship between the IWF and other SIP and H.323 entities is shown in Figure 1. H.323 Entity SIP Entity +---------------+ | H.323 GK | +----------------+ | |\ | Proxy/Redirect | +---------------+ \ | Server | \ /+----------------+ \ / +---------------+ +---------------+/ | H.323 MCU |----| Interworking | | MC,or Terminal| | Function | +---------------+ +---------------+\ / \ / \+----------------+ +---------------+ / | SIP | | H.323 Gateway |/ | User Agent | | | +----------------+ +---------------+ Figure 1 : Logical Relationship between IWF and SIP/H.323 entities 3. Background Two standards are currently popular for IP telephony signaling: the H.323 protocol suite by ITU-T, and the Session Initiation Protocol (SIP) by IETF. Both of these signaling protocols provide mechanisms for call establishment and teardown, call control and supplementary services, and capability exchange. In terms of functionality and services that can be supported, H.323 version 2 [5] and SIP Version 2 [3] are very similar. However, supplementary services in H.323 are more rigorously defined, and therefore fewer interoperability issues are Agarwal, et al. [Page 4] Internet Draft SIP-H.323 Interworking February 2001 expected among its implementations. Furthermore, H.323 has taken more steps to ensure compatibility among its different versions, and to interoperate with PSTN. SIP's primary advantages are (i) flexibility to add new features, and (ii) relative ease of implementation and debugging. H.323 and SIP are improving themselves by learning from each other, and the differences between them are diminishing with each new version. At present, H.323 and SIP networks are coexisting with different service providers in many parts of the world as they think to provide services to satisfy their customers' needs. SIP-H.323 IWF is a solution for those service providers who want to support both H.323 and SIP networks. There are different forums involved in the standardization of SIP-H.323 IWF. The aim of all these forums is to provide an agreed upon specifications so that there will be no interoperability issues between different vendor implementations. This work is also under progress in ETSI TIPHON and IMTC aHit! forums. 4. Scope of this document This document describes interworking between H.323 Version 2.0 [5] and SIP Version 2.0 [3]. However, since H.323v2 terminal may or may not support FastConnect, solutions without using this feature are also detailed in this document. This Interworking recommendation is being defined in two phases. The Current (first) phase defines the basic call establishment, call termination. It also defines the translation between H.245 and SDP for session description. The second phase will include optional messaging of the two protocols, advanced features and services. Both phases have to meet the general requirements specified in the SIP-H323 Interworking Requirement draft [9]. The support for future versions of H.323 and SIP MAY be addressed in the next phase. 5. Definitions Agarwal, et al. [Page 5] Internet Draft SIP-H.323 Interworking February 2001 Endpoint (EP): This is an entity from which the media originates or finally terminates. This can either be H.323 terminal or SIP user agent. H.323 Gatekeeper (GK) : The Gatekeeper (GK) is an OPTIONAL H.323 entity on the network that provides address translation and controls access to the network for H.323 terminals, Gateways and MCUs. The Gatekeeper may also provide other services to the terminals, Gateways and MCUs such as bandwidth management and locating Gateways. H.323 Terminal: A H.323 Terminal is an endpoint on the network which provides the real-time, two-way communications with another H.323 terminal, Gateway, or Multipoint Control Unit. This communication consists of control, indications, audio, moving color video pictures, and/or data between the two terminals. A terminal may provide speech only, speech and data, speech and video, or speech, data and video. H.323 Side: The H.323 side of the IWF is the part of the IWF that terminates and originates H.323 signaling from and to the H.323 network respectively. Interworking Function (IWF): It allows interworking between the H.323 and SIP networks. Media Switching Function (MSF): This is an OPTIONAL logical entity present in the IWF, which will perform the task of switching RTP from one logical port to other. SIP User Agents (UA): A logical entity which can act as both SIP user agent client and SIP user agent server. SIP Server: This can be either SIP Proxy, Redirect, Location or Registrar server. SIP Proxy Server: A logical entity which acts as both server and a client. SIP messages will be processed and passed to other SIP entities. A SIP proxy server interprets, and, if necessary, rewrites a SIP message before forwarding it. Agarwal, et al. [Page 6] Internet Draft SIP-H.323 Interworking February 2001 SIP Redirect Server: A logical entity which is primarily used for address translation and locating a SIP user. It may take the help of location server for locating a SIP user. SIP redirect server does not accept calls and does not initiate a SIP request on behalf of a calling SIP endpoint. SIP redirect server sends a response to a request for locating a SIP user. SIP Location Server: A location service is used by a SIP proxy or SIP redirect server to obtain information about the callee's possible location(s). SIP Registrar Server: A SIP registrar is a server that accepts REGISTER requests from SIP endpoints. A SIP registrar is typically co-located with a SIP proxy or SIP redirect server and MAY make its information available through the location server. SIP Side: The SIP side of the IWF is the part of the IWF that terminates and originates SIP signaling from and to the SIP network respectively. 6. Overview of IWF Functionality When the IWF receives call signaling messages from an H.323 entity, it performs the necessary translation and sends the corresponding equivalent messages to SIP entity and vice versa. The IWF SHALL provide signaling translation for all phases of a call. This IWF does not include media format conversion. However, it MAY include a Media Switching Function for switching RTP packets which is out of scope of this document. There are several scenarios where SIP-H.323 IWF can be placed with different network elements in the SIP and H.323 networks. The way the messages are generated during a call establishment between H.323 EP and a SIP UA, is different depending on the scenario. Scenario 1: IWF without H.323 GK and SIP Server +----------+ +--------+ +--------+ | | | | | | Agarwal, et al. [Page 7] Internet Draft SIP-H.323 Interworking February 2001 | H.323 EP |<---------------->| IWF |<----------------->| SIP UA | | | | | | | +----------+ +--------+ +--------+ Scenario 2: IWF with H.323 GK and without SIP Server +----------+ +----------+ +--------+ +---------+ | | | | | | | | | H.323 EP |<->| H.323 GK |<->| IWF |<---------------->| SIP UA | | | | | | | | | +----------+ +----------+ +--------+ +---------+ Scenario 3: IWF with SIP Server and without SIP Server +----------+ +--------+ +----------+ +---------+ | | | | | Proxy or | | | | H.323 EP |<---------------->| IWF |<->| Redirect |<->| SIP UA | | | | | | Server | | | +----------+ +--------+ +----------+ +---------+ Scenario 4: IWF with H.323 Server and SIP Server +------_---+ +----------+ +--------+ +----------+ +--------+ | | | | | | | Proxy or | | | | H.323 EP |<->| H.323 GK |<->| IWF |<->| Redirect |<->| SIP UA | | | | | | | | Server | | | +----------+ +----------+ +--------+ +----------+ +--------+ 7. Interworking Requirements for IWF The requirement for SIP-H.323 IWF has already been addressed in detail in "SIP-H.323 Interworking Requirements" [9]. The summary of SIP-H.323 interworking requirements is given for reference in Appendix D. 8. Mapping Between SIP and H.323 in IWF 8.1. Addresses Mapping Agarwal, et al. [Page 8] Internet Draft SIP-H.323 Interworking February 2001 There are different formats of alias addresses in H.323 and the corresponding addresses in SIP. H.323 Version 2 supports the following schemes of alias addresses: H323Id, E164Id, Email Id, url Id, transport Id and partyNumber H.323 Version 1 supports only H323Id and E164Id. The ASN.1 description of an H.323 Alias Address in H.323 Version 2 is: H323-Alias-Address ::= CHOICE { e164 IA5String (SIZE(1..128)) (FROM("0123456789#*,")), h323-ID BMPString (SIZE (1..256)), ..., url-ID IA5String ( SIZE(1 .. 512)),-- URL Style address transport-ID TransportAddress, -- IPv4, IPv6, IPX etc.,... email-ID IA5String (SIZE(1..512)), -- rfc822 compliant email address partyNumber PartyNumber } The PartyNumber parameter that contains public numbering plan or data/telex/private/public numbering digits is not described in this document and is left for further study. On the other hand, SIP address can be defined by the following BNF from the description provided in RFC 2543 [3]: SIP-Address - (name-addr | addr-spec) name-addr - [display-name] "<" addr-spec ">" addr-spec - SIP-URL|URI SIP-URL - "sip:"[userinfo"@"]hostport url-parameters [headers] userinfo - [user|telephone-subscriber][":"password] user - *(unreserved|escaped|"&"|"="|"+"|"$"|"," |";"|"?"|"/") password - *(unreserved|escaped|"&"|"="|"+"|"$"|",") hostport - host[":"port] host - hostname|Ipv4address|IPV6reference Agarwal, et al. [Page 9] Internet Draft SIP-H.323 Interworking February 2001 hostname = *( domainlabel "." ) toplabel [ "." ] domainlabel = alphanum | alphanum *( alphanum | "-" ) alphanum toplabel = alpha | alpha *( alphanum | "-" ) alphanum IPv4address = 1*digit "." 1*digit "." 1*digit "." 1*digit port = *digit url-parameters - *(";"url-parameter) url-parameter - transport-param | user-param | method-param | ttl-param | maadr-param | other-param ttl = 1*3DIGIT ; 0 to 255 maddr-param = "maddr=" host user-param = "user=" ( "phone" | "ip" ) method-param = "method=" Method other-param = ( token | ( token "=" ( token | quoted-string ))) headers = "?" header *( "&" header ) header = hname "=" hvalue hname = 1*uric hvalue = *uric uric = reserved | unreserved | escaped reserved = ";" | "/" | "?" | ":" | "@" | "&" | "=" | "+" | "$" | "," digits = 1*DIGIT The SIP URI components can be described as stated below : telephone-subscriber = global-phone-number | local-phone-number global-phone-number = "+" 1*phonedigit [isdn-subaddress] [post-dial] local-phone-number = 1*(phonedigit | dtmf-digit | pause-character) [isdn-subaddress] [post-dial] isdn-subaddress = ";isub=" 1*phonedigit post-dial = ";postd=" 1*(phonedigit | dtmf-digit | pause-character) phonedigit = DIGIT | visual-separator visual-separator = "-" | "." pause-character = one-second-pause | wait-for-dial-tone one-second-pause = "p" wait-for-dial-tone = "w" dtmf-digit = "*" | "#" | "A" | "B" | "C" | "D" Agarwal, et al. [Page 10] Internet Draft SIP-H.323 Interworking February 2001 Alias address are mapped based on procedures described in the subsequent sections. 8.1.1. Converting SIP Addresses to H.323 Addresses * E164 SIP URL which contains the "user=phone" and does not contain a "w" in the user part will be mapped to E164 Id of H323. The e164 field only allows characters from the set "0123456789#*,". Thus, any leading "+" is removed from the SIP telephone-subscriber part, as are any visual separators "-" and ".". For example: +1-978-985-7193 will be converted to "19789857193". The pause "p" is replaced with ",". If the phone number exceeds 128 characters, the IWF generates a SIP response of 414 (Request-URI Too Long). E164 in H.323 can be either E.164 number in H.323 Alias Address or it may also be derived from the caller/callee number in Q.931 messages. * H323Id In most of the cases, userinfo part of SIP URL will be mapped to H323 Id of H323. Each BMP character in h323-ID stores the corresponding text character in the SIP Address. (BMP stands for basic multilingual plane i.e., Basic ISO/IEC 10646-1 (unicode) character set). The h323-ID MUST always be generated so that a terminal running version 1.0 of H.323 (which supports only e164 and h323-ID, but does not support transport-ID, url-ID or email-ID) can still decode the address. If the SIP-Address contains more than 256 characters, only the addr- spec part is copied. If the addr-spec exceeds 256 characters, the IWF generates a SIP response of 414 (Request-URI Too Long). * Email Agarwal, et al. [Page 11] Internet Draft SIP-H.323 Interworking February 2001 If the SIP URL looks like an Email Id i.e. user@group, then it will be mapped to Email Id of H323. To indicate an email-like address, an H.323v1 entity shall send it in H323-ID and prefix it with the seven characters "mailto:". In this case the string after the colon must be an RFC 822 compliant email address. An example of such an address is as follows: mailto:abc@company.com If the size exceeds 512 characters, the IWF generates the SIP status 414 (Request-URI Too Long). * Transport Id If the SIP URL contains the IPV4 address in the host part, then it will be mapped to the transport Id of H323. To indicate an IP-like address, an H.323v1 entity shall send it in H323-ID and prefix it with the three characters "ip:". In this case the string after the colon must contain an address in dotted decimal form, with an optional colon and port number at the end. An example of such an address is as follows: ip:10.0.0.1:5050. If a port parameter is present in the SIP address, the number is used. Otherwise, the port number depends on the context. For example, for the destination address of H.323 SETUP messages, it is set to 1720, otherwise it is set to 0. * URL Id If the SIP URL looks like a url i.e., user@domain, then it will be mapped to the url Id of H323. If the SIP URL exceeds 512 bytes in size, the IWF generates the SIP status 414 (Request-URI too long). 8.1.2. Examples of Address Resolution o The SIP Address "sip:j.doe@big.com" is converted to H.323 Address: { h323-ID = "sip:j.doe@big.com", url-ID = "sip:j.doe@big.com", email-ID= "j.doe@big.com" } Agarwal, et al. [Page 12] Internet Draft SIP-H.323 Interworking February 2001 o The SIP Address "sip:+1-212-555-1212:1234@iwf.com; user=phone" is converted to H.323 Address: { e164 = "12125551212", h323-ID = "sip:+1-212-555-1212:1234@iwf.com", url-ID = "sip:+1-212-555-1212:1234@iwf.com", email-ID= "+1-212-555-1212:1234@iwf.com" } o The SIP Address "sip:alice@10.1.2.3" is converted to H.323 Address: { h323-ID = "sip:alice@10.1.2.3", url-ID = "sip:alice@10.1.2.3", tranport-ID = IPAddress 10.1.2.3:1720, email-ID = "alice@10.1.2.3" } o The SIP Address "A. Bell " is converted to H.323 Address: { h323-ID = "A. Bell", url-ID = "sip:a.g.bell@bell-tel.com", email-ID = "A. Bell " } 8.1.3. Converting H.323 Addresses to SIP Addresses *E164 Id It will be put in a SIP URL with a telephone number. The number will either be globalized or left as a local number in which case it will require the information of From header. "phone-context" is used to represent the local number. sip:telephone-subscriber@host; user = phone For Example: E164Id = +1-719-227-9665 can be mapped to sip:+1-719-227-9665@host;user=phone Agarwal, et al. [Page 13] Internet Draft SIP-H.323 Interworking February 2001 'host' is a host name (domain name of IPv4 address) followed by an optional port number. It is a mandatory in SIP URL. The E164 Id in H.323 does not provide any direct information of the host part of the SIP URL (the host part should identify a SIP server with the IPv4 address of the domain name). The host part may be determined using some specialized service either by location server or by pre-provisioning in IWF. If Called/Calling Party Number is present in H.323 messages (other than UUIE part of Q.931 message), it may be treated like a E164 Id and mapping may be done as discussed above. *H323 Id It will be mapped to userinfo part of SIP URL. *Email Id It will be mapped to SIP-URL/URI after adding the "sip:" prefix. For Example: email ID = userA@gateway.iwf.com will be mapped to sip:userA@gateway.iwf.com *url Id It will be mapped to SIP URL after adding the "sip" prefix if it is not present in the url Id. For Example: url Id = h225://userA@gateway.iwf.com:2030 will be mapped to sip:userA@gateway.iwf.com:2030 *Transport Id It will be mapped to host part of SIP URL if it is a IPv4 address. User part of SIP URL in this case may be mapped to either H323 Id, Email Id or E164 Id. If no port is specified then the default port number 5060 will be used.The IWF SHOULD not map transport Id to SIP URL if it corresponds to the IP address of IWF itself. In this case, the other aliases will reflect the callee address. For Example: Transport Id = 164.164.28.132 can be mapped to sip:164.164.28.132:5060 Transport Id = 164.164.28.132:2030 can be mapped to sip:164.164.28.132:2030 Agarwal, et al. [Page 14] Internet Draft SIP-H.323 Interworking February 2001 Zone prefix in H.323 non-standard parameter of registration MAY be used during address resolution on H.323 Gatekeeper. This will be further discussed in next release of this draft. 8.2. Message Mapping Some of the SIP and H.323 messages have direct one to one mappings. These are listed below. These tables hold good for both conversions i.e. SIP messages to H.323 messages and vice versa. SIP Message H.323 Message ------------ ------------- 100 Trying H.225 Call Proceeding 180 Ringing H.225 Alerting 183 Session Progress H.225 Call Proceeding 301 Moved Permanently RRQ with updated Address of SIP's Contact header field (If GK is present) or update local lookup table. 380 Alternative Service H.225 Facility 400 Bad Request H.225 ReleaseComplete (reason=undefinedReason) 401 Unauthorized H.225 ReleaseComplete (reason=securityDenied) 402 Payment Required H.225 ReleaseComplete (reason=undefinedReason) 403 Forbidden H.225 ReleaseComplete (reason=noPermission) 404 Not Found H.225 ReleaseComplete (reason=unreachableDestination) 405 Method Not Allowed H.225 ReleaseComplete (reason=undefinedReason) 406 Not Acceptable H.225 ReleaseComplete (reason=undefinedReason) 407 Proxy Auth. Required H.225 Release Complete (reason=noPermission) 408 Request Timeout H.225 ReleaseComplete (reason=adaptiveBusy) Agarwal, et al. [Page 15] Internet Draft SIP-H.323 Interworking February 2001 409 Conflict H.225 ReleaseComplete (reason=undefinedReason) 410 Gone H.225 ReleaseComplete (reason=unreachableDestination) 413 Request Entity Too Large H.225 ReleaseComplete (reason=badFormatAddress) 414 Request-URI Too Large H.225 ReleaseComplete (reason=badFormatAddress) 415 Unsupported Media Type H.225 ReleaseComplete (reason=undefinedReason) 420 Bad Extension H.225 ReleaseComplete (reason=badFormatAddress) 480 Temporarily not available H.225 ReleaseComplete (reason=adaptiveBusy) 481 Call Leg/Transaction H.225 ReleaseComplete Does Not Exist (reason=undefinedReason) 482 Loop Detected H.225 ReleaseComplete (reason=undefinedReason) 483 Too Many Hops H.225 ReleaseComplete (reason=undefinedReason) 485 Ambiguous H.225 ReleaseComplete (reason=badFormatAddress) 486 Busy Here H.225 ReleaseComplete (reason=destinationRejection) 487 Request Terminated H.225 ReleaseComplete (reason=undefinedReason) 488 Not Acceptable Here H.225 ReleaseComplete (reason=undefinedReason) 500 Server Internal Error H.225 ReleaseComplete (reason=undefinedReason) 501 Not Implemented H.225 ReleaseComplete (reason=invalidRevision) 502 Bad Gateway H.225 ReleaseComplete (reason=gatewayResources) 503 Service Unavailable H.225 ReleaseComplete (reason=gatewayResources) 504 Server Time-out H.225 ReleaseComplete (reason=adaptiveBusy) 505 Version Not Supported H.225 ReleaseComplete (reason=invalidRevision) Agarwal, et al. [Page 16] Internet Draft SIP-H.323 Interworking February 2001 600 Busy Everywhere H.225 ReleaseComplete (reason=destinationRejection) 603 Decline H.225 ReleaseComplete (reason=destinationRejection) 604 Does not exist anywhere H.225 ReleaseComplete (reason=unreachableDestination) 606 Not Acceptable H.225 ReleaseComplete (reason=undefinedReason) INFO H.245 UserInputIndication BYE H.245 EndSessionCommand (H.225 ReleaseComplete message needs to be sent to close the Call Signaling Channel, if it is open) Table 1: One to One Mapping of SIP and H.323 Messages H.323 Message SIP Message ------------- ----------- H.245 sendTerminalCapabilitySet OPTIONS H.245 EndSessionCommand BYE H.225 Release Complete CANCEL or BYE(if call is connected) RAS DRQ CANCEL or BYE(if call is connected) In most of the cases, the error messages from SIP side like 4xx, 5xx and 6xx will be mapped to H.225 Release Complete message. The ReleaseCompleteReason will describe the type of error on the SIP side. Some of the error messages on one side may not always map to a corresponding error message on the other side. The ASN.1 description of an H.225 ReleaseCompleteReason in H.323 Version 2 is: ReleaseCompleteReason ::= CHOICE { noBandwidth NULL,-- bandwidth taken away or ARQ denied gatekeeperResources NULL,-- exhausted unreachableDestination NULL,-- no transport path to the destination destinationRejection NULL,-- rejected at destination invalidRevision NULL, Agarwal, et al. [Page 17] Internet Draft SIP-H.323 Interworking February 2001 noPermission NULL,-- called party's gatekeeper rejects unreachableGatekeeper NULL,-- terminal cannot reach gatekeeper for ARQ gatewayResources NULL, badFormatAddress NULL, adaptiveBusy NULL,-- call is dropping due to LAN crowding inConf NULL,-- no address in alternativeAddress undefinedReason NULL, ..., facilityCallDeflection NULL,-- call was deflected using a Facility message securityDenied NULL,-- incompatible security settings calledPartyNotRegistered NULL,-- used by gatekeeper when endpoint has preGrantedARQ to bypass ARQ/ACF callerNotRegistered NULL -- used by gatekeeper when endpoint has preGrantedARQ to bypass ARQ/ACF } 8.3. Call Sequence Mapping Some of the messages from either SIP side or H.323 side invokes a fixed call sequence (series of messages) i.e. exchange of more than one messages on other side. These call sequences are given below: SIP Message H.323 Message Sequence ----------- ---------------------- BYE H.245 End Session Command H.225 Release Complete RAS DRQ H.323 Message SIP Message Sequence ------------- -------------------- DRQ 4XX BYE or CANCEL 8.4. Message Parameters Mapping Agarwal, et al. [Page 18] Internet Draft SIP-H.323 Interworking February 2001 This section contains the mapping of every possible parameter of all mandatory messages of H.323 and SIP. Details will be added in the next release of the draft. 8.5. Audio/Video Formats Mapping A subset of IANA-registered formats and H.323-supported capabilities are listed in Table 2. H.323 Codec IANA Codec Payload Type Clock/channels ------------------------------------------------------------- g711Alaw64k PCMA 8 8000/1 g711Ulaw64k PCMU 0 8000/1 g711Alaw56k N/A g711Ulaw56k N/A g722-64k G722 9 8000/1 g722-56k N/A g722-48k N/A g7231 G723 4 8000/1 g728 G728 15 8000/1 g729 G729? Dynamic/18? 8000/1 g729AnnexA ? Dynamic 8000/1 g729wAnnexB ? g729AwB ? g7231AnnexC ? gsmFullRate GSM 3 8000/1 gsmHalfRate GSM-HR Dynamic 8000/1 gsmEnhFullRate GSM-EFR Dynamic 8000/1 h261VideoCap H261 31 90000 h262VideoCap ? h263VideoCap H263 34 90000 Table 2 : Mapping of Codecs Note:H.323 only supports a clock rate of 8000 Hz; other values cannot be mapped to H.323. Agarwal, et al. [Page 19] Internet Draft SIP-H.323 Interworking February 2001 SDP attribute "ptime" gives the maximum length of time in milliseconds represented by media in a packet. This MAY be used for defining the maximum packet length. A fmtp SDP attribute for silence suppression SHOULD be defined if silence suppression is on. Another possible fmtp attribute MAY be the list of annexes which are supported. This MAY be useful in translating g729AnnexB, g729AnnexAwAnnexB, g7231AnnexC and so on to SDP. The Video MPI (Mean Picture Interval) SHOULD mapped to the SDP attribute "framerate" as follows: mpi = 30 / framerate It is assumed that 29.97 Hz is rounded to 30 Hz when calculating the framerate. So MPI of 1 become framerate 30.0, similarly MPI of 2 becomes framerate 15. However, the IWF shall do proper rounding error correction on the incoming side. So framerate of 29.97 should also map to MPI of 1. Note that in SDP any possible value for framerate is allowed, but in H.323 only multiples of 1/29.97 are allowed. The IWF should convert the framerate to the next lower value allowed in H.323. For example, a framerate of 12.3 frames per second in SDP is converted to an MPI value of 3 which is equivalent to 10 frames per second. 9. Basic Message Handling 9.1. H.323-originated Requests Received by IWF a) Calls from H.323 network directed towards IWF MAY contain the Agarwal, et al. [Page 20] Internet Draft SIP-H.323 Interworking February 2001 signaling address of IWF in the destination address and the SIP address in remote extension address of Setup message. In these cases, remote extension address will be used to route the call else destination alias address will be resolved to the corresponding IP address or SIP Server address. b) Call from H.323 network directed towards IWF MAY contain the destination address, terminal capabilities and channel information in different messages. This information SHALL be combined and mapped to create the SDP information of INVITE or ACK. 9.1.1 IWF Receives RAS Message (a) DRQ If the call is active, close it. Send RAS DCF (disengage confirm) and Release Complete to H.323 entity. The corresponding 4xx, 5xx or 6xx message will also be sent to the SIP side of the network. 9.1.2 IWF Receives a Q.931 Messages (a)Setup The IWF generates an ARQ/ACF sequence if required here as per H.323 standard. However, that is local to the H.323 stack and does not affect translation. If fastStart is present, convert it to H.323 capability set, else build some default H.323 capability set. The IWF SHALL send a Q.931 CallProceeding message immediately on receiving a Call Setup message from H.323 entity. The IWF then sends an INVITE, where the SIP To header field is derived from the Q.931 destinationAliasAddress and/or destCallSignalAddress. If destinationAddress is the IWF itself, then use remoteExtensionAddress. The From SIP header field is derived from sourceAliasAddress and/or srcCallSignalAddress. The session description is constructed from the H.323 capability set.If the IWF receives a 2xx response for the INVITE, it updates the SIP capability set using the session description in the response body. It then sends a Q.931 Connect message to the H.323 entity.Then, the IWF sends an ACK request to the SIP entity. Then, it sends an H.245 TCS to the H.323 entity using the SIP capability set. It then completes the opening of channels in both the directions. If the IWF receives a 180 (Alerting) SIP response, send a Q.931 Alerting message to the H.323 entity. Agarwal, et al. [Page 21] Internet Draft SIP-H.323 Interworking February 2001 If the IWF receives any other 1xx SIP response, it sends a Q.931 CallProceeding message to H.323, but only if not already sent for this call. If no response is received or a failure response, the IWF sends a Q.931 ReleaseComplete message to the H.323 entity. (b) Q.931 ReleaseComplete If the IWF receives a Q.931 ReleaseComplete, the H.323 side of the call is closed. The IWF sends a BYE to the SIP entity if the call has been established. 9.1.3 IWF Receives H.245 Messagers (a) Terminal Capability Message If it receives a Terminal Capability Set (TCS), it updates the H.323 capability set and calculates the maximal intersection of the H.323 and SIP capability sets, called C. From C, the IWF derives a suitable operating mode (say M). For each element in M in the direction from SIP to H.323,send a H.245 Open Logical Channel (OLC) to the H.323 entity. The OLC messages use the transport addresses of the SIP capability set, derived from the session description in the 2xx response body. When an IWF receives a TCS message , it will be mapped to the "m=" line of SDP with each line containing only one payload type. (b) Open Logical Channel/ACK/REJ If the IWF receives an OLC and the logical channel is present in the operating mode from H.323 to SIP, it responds with an OLCAck. The OLCAck uses the transport addresses of the SIP capability set. If the logical channel is not present in the operating mode, the IWF sends an OLCReject .Once the IWF has received OLCAck or OLCRej for all the requests, update the operating mode. Then, the IWF sends a re-INVITE. The session description is formed using the new operating mode if it is different from what was sent in the first INVITE message and the transport addresses received in OLCAcks. The IWF should wait for a 2xx response from the SIP entity and respond with an ACK request. If it times out or if it fails, it should close the call. (c) Mode Request or Change in Logical Channels Agarwal, et al. [Page 22] Internet Draft SIP-H.323 Interworking February 2001 Update operating modes, Send re-INVITE to SIP entity. If that fails then reject the Mode Request or Open Logical Channel request. (d) H.245 EndSession If the IWF receives a H.245 EndSession, it closes the H.245 call. Send H.245 EndSession and Q.931 ReleaseComplete to H.323 entity and send RAS DRQ to gatekeeper if it admitted the call. (e) When an IWF receives a UserInputIndication message, it MAY be sending the DTMF to SIP using SIP INFO method. Only the alphanumeric method of userinputIndication is considered for this release of the draft. Other mapping between the INFO msg body and the signal type of userinput is left for further study. IWF MAY use a proprietary non-INFO method based solution that interworks with H.245 UserInputIndication. IWF May Use a proprietary INFO method based solution that interworks with H.245 UserInputIndication. IWF May Use a proprietary/standard non-INFO method based solution that could backhaul in-band DTMF signaling to the IWF and which would interwork with H.245 UserInputIndication 9.2. SIP-originated Requests Received by IWF (a) INVITE for a New Call The IWF SHALL respond with a 100 (Trying) response to the SIP entity immediately after receiving the INVITE request. It stores the SDP information as the terminal's SIP capability and convert the SIP UA capabilities to create the H.245 TCS. If the IWF is registered with a gatekeeper, send a RAS ARQ message to the gatekeeper, where the destinationInfo and destCallSignalAddress is derived from the To SIP header, the sourceInfo is derived from the From SIP header field and sourceCallSignalAddress is the call signaling address of the IWF itself. The gatekeeper assigns an endpointIdentifier during registration. That value of endpointIdentifier is used in the endpointIdentifier field of the ARQ message. Next, the IWF should receive either a RAS ACF or ARJ message. If an ACF message is received, establish an Q.931 channel as described below. If an ARJ message is received, the behavior depends on the reason parameter: Agarwal, et al. [Page 23] Internet Draft SIP-H.323 Interworking February 2001 CalledPartyNotRegistered: The IWF responds with 404 (Not Found). callerNotRegistered: The IWF MAY register, with a RAS RRQ message, the SIP address with the gatekeeper and then retransmit the RAS request, with the endpointIdentifier returned in RCF. Alternatively, it MAY send a 400 (Caller not registered) response to the SIP entity. incompleteAddress: Send 484 (Address Incomplete) response to SIP entity. Other reasons: Send 400 (Bad Request) response to SIP entity for H.323 translation failure. If the IWF times out waiting for an ARQ response, it sends a SIP 504 (Gateway time-out) response. If the IWF is not registered with a gatekeeper and it is able to resolve the SIP address to a H.323 address or if the IWF is registered and has received an ACF for the registration request from the gatekeeper, the IWF sends a Q.931 SETUP message to the H.323 entity, where the sourceAddress is derived from the SIP From header,the destinationAddress is derived from the SIP To header or from the RAS ACF response, destCallSignalAddress is derived from the RAS ACF response or from the To SIP header. The remoteExtensionAddress is copied from RAS ACF if present or extracted from To SIP header if possible. The sourceCallSignalAddress is the call signaling transport address of the IWF. fastStart PDUs are mapped from the session description in the INVITE message body. Each SDP payload type entry is converted to an OLC message. All the payload types on the SDP same media description line have the same session id in the OLC messages. This identifies them as belonging to the same group and the receiving H.323 entity will select one of these. (TBD: needs more description) If the IWF receives a Q.931 CallProceeding message, send a 100 (Trying) response to the SIP entity, if not already sent. If fastStart PDUs are present, store them. If the IWF receives a Q.931 Alerting message, send a 180 (Alerting) response to the SIP entity, indicating that the final destination is ringing. If fastStart PDUs are present, store them. If the IWF receives a Q.931 Connect message, the behavior depends on whether a FastStart indication is present. If a FastStart indication is present, the IWF maps the received OLCs to the SDP payload types Agarwal, et al. [Page 24] Internet Draft SIP-H.323 Interworking February 2001 contained in the original INVITE request. Format a new SDP packet with more constrained media description and correct media transport address of the H.323 entity. Now each media description line will contain a single payload type, depending on which OLC PDUs are present. The operating mode and H.323 capability set are set to this reduced set of payloads. The SDP message is sent in a 200 (OK) response. The IWF then waits for the ACK request from the SIP entity. If the IWF times out, it declares the call closed and terminates the H.323 call. Once an ACK has been received, the IWF may proceed with other H.245 signaling (CESE, RTDSE and so on). If the H.323 entity does not support FastStart, the IWF proceeds with H.245 signaling as described below. First, it sends a TCS to the the H.323 entity and uses the stored SIP capability set to generate the H.245 capabilities. If the IWF receives an H.245 TCS message, it updates the H.323 capability set and calculates maximal intersection of H.323 and SIP capability sets (call this C). Derive a suitable operating mode from C (say, M). For each element in M (for the data from the SIP UA to the H.323 terminal), send an H.245 OLC message to the H.323 entity. Use the transport address of the SIP capability set, derived from the SDP received in the original INVITE message. If the IWF receives an OLC message and the logical channel is present in the operating mode from the H.323 terminal to the SIP UA, the IWF sends an OLCAck to the H.323 terminal. The OLCAck contains the transport address from the SIP capability set, again derived from the SDP in the INVITE message body. If the logical channel is not present in that operating mode, the IWF sends an OLCReject. Once the IWF has received an OLCAck or OLCRej for all outstanding OLC requests, it updates the operating mode and sends a 200 (OK) response to the SIP entity. The session description in that response is formed using the new operating mode and the transport addresses received in the H.245 OLCAcks. The IWF should wait for the ACK request from the SIP entity. If the IWF times out, it should close the H.323 call. This concludes the description of the non-FastStart handling. Agarwal, et al. [Page 25] Internet Draft SIP-H.323 Interworking February 2001 If, at any time, the IWF receives a Q.931 ReleaseComplete message, a H.323 call could not be established. The IWF sends a 400 (Bad Request) for the request failure with reason phrase "H.323 call failed". If the Q.931 SETUP times out, the IWF sends a 504 (Gateway time-out) response. If the SIP address is not resolved to an H.323 address, send a 501 (Not Implemented) response to SIP entity. (c) INVITE for an Existing Call o Update the SIP capability set. o Recalculate the operating mode, minimizing changes. An H.245 Mode Request message is sent if the operating mode has changed. If the Mode Request fails, either close the media channel or the call. (d) BYE Request The IWF sends an H.245 Endsession to the H.323 entity. Upon receipt of a response or on timeout, the IWF sends a Q.931 ReleaseComplete to H.323 entity. If the call was admitted by a GK, send a RAS DRQ (Disengage Request) message to the GK. (e) OPTIONS Request TBD: how do we query H.323 capabilities without establishing the Call because there is no standard mechanism in H.323? The IWF sends a RAS RRQ message to the H.323 GK, where the callSignalAddress is the address of the IWF, the terminalType is set to "gateway" and the terminalAlias is mapped from the To header of the REGISTER request. The IWF stores the SIP Contact header field. A "200 OK" SIP status response is sent after receiving a RAS RCF message. 10. Interworking Call Scenarios for Different Configurations Agarwal, et al. [Page 26] Internet Draft SIP-H.323 Interworking February 2001 In cases where SIP Server or H.323 GK coexists with IWF, they will still be treated as separate logical entities. This is because seperate instances of H.323 stack will be running for H.323 GK and IWF. Similarly, there will be seperate instances of SIP stack running at both IWF and SIP server. All call flow diagrams will therefore shows IWF as a seperate logical entity and SHALL always include call messaging between IWF and H.323 GK/SIP Server (if they exists). 10.1. Registration and Address Resolution Services 10.1.1. Registration In H.323, registration is the process by which an endpoint joins a Zone,and informs the Gatekeeper of its Transport Address and alias addresses.As a part of their configuration process, all endpoints shall register with the Gatekeeper identified through the discovery process. Registration shall occur before any calls are attempted and may occur periodically as necessary (for example, at endpoint power-up or before registration timeout). An endpoint shall send a Registration Request (RRQ) message to a Gatekeeper. This is sent to the Gatekeeper's RAS Channel Transport Address. The endpoint has the Network Address of the Gatekeeper from the Gatekeeper discovery process and uses the well-known RAS Channel TSAP Identifier. The Gatekeeper shall respond with either a Registration Confirmation (RCF) or a Registration Reject (RRJ) message. In SIP, the REGISTER request allows a client to let a proxy or redirect server know at which address(es) it can be reached. A client MAY also use it to install call handling features at the server. A client uses the REGISTER method to register the address listed in the To header field with a SIP server. The Register request MAY contain a Contact header field; future non- REGISTER requests for the URI given in the To header field SHOULD be directed to the address(es) given in the Contact header. A user agent MAY register with a local server on startup by sending a REGISTER request to the well-knowwn "all SIP servers" multicast address Agarwal, et al. [Page 27] Internet Draft SIP-H.323 Interworking February 2001 "sip.mcast.net" (224.0.1.75). This request SHOULD be scoped to ensure it is not forwarded beyond the boundaries of the administrative system. The unicast method can also be used for registration if address of the registration is known. The SIP server registers the user in its contact database and returns a response 200 OK to the user's SIP client. The response includes the user's current contact list in Contact headers. During initialization, the IWF MAY registers its own alias address (e.g., gw1) with its local H.323 gatekeepers, so that anybody from the H.323 cloud can reach SIP endpoints by directly connecting to the alias address of the IWF and by providing a SIP address in the remote extension address of the SETUP message of H.323. 10.1.2. Address Resolution In H.323, an endpoint or Gatekeeper which has an alias address for an endpoint and would like to determine its contact information may issue a Location Request (LRQ) message. This message may be sent to a specific Gatekeeper's RAS Channel TSAP Identifier, or may be multicast to the Gatekeeper's well-known Discovery Multicast Address. The Gatekeeper with which the requested endpoint is registered, shall respond with the Location Confirmation (LCF) message containing the contact information of the endpoint or the endpoint's Gatekeeper. Contact information shall include the Call Signalling Channel and RAS Channel addresses to be used to reach the endpoint and optionally additional destination information which can provide dialling information and extension information concerning the requested endpoint. All Gatekeepers with which the requested endpoint is not registered, shall return Location Reject (LRJ) if they received the LRQ on the RAS Channel. Any Gatekeeper with which the requested endpoint is not registered, shall not respond to the LRQ, if it received the LRQ on the Discovery Multicast address. In SIP, the REGISTRATION method is used to register the address(es) of the user in the SIP server (register, redirect, proxy) and the SIP server registers the address(es) in its contact database. A SIP Agarwal, et al. [Page 28] Internet Draft SIP-H.323 Interworking February 2001 register/redirect/proxy server returns the list to the client as Contact headers. A SIP register/redirect/proxy server can return the address(es) where the user can be contacted. The OPTION method of SIP can also be used to resolve the addresses. For example, the SIP server may be queried for knowing its capabilities using the OPTION method. If the server that believes it can contact the user, such as a user agent where the user is logged in and has been recently active, MAY respond to this request with a capability set along with the address(es) where the user can be contacted. 10.1.3. Registration and Address Resolution Scenarios An RRQ contains an endpointType, which will, in the IWF case, contain a GatewayInfo SEQUENCE that contains the SupportedProtocols. In H.323v2, each of these SupportedProtocols contains a SEQUENCE OF dial prefixes. This is where the number ranges are specified by way of prefixes. Also, most GKs support some form of static configuration to do the same job by less elegant means if either IWF or GK is version 1 or doesn't support this feature for other reasons. This method of dial prefixes and number range will help in address resolution in cases when the SIP and H.323 domain is well defined with a dialing plan. * Registered as SIP User Agent (to register as an IWF, TRIP may be used, but left for further study) 10.1.4. Advertisement of SIP Support by H.323 Gateways As the Session Initiation Protocol (SIP) gains wider acceptance, it is important to build gateways that provide an interworking function between the two protocols. It is our recommendation that we add SIP to the list of supported protocols advertised by an H.323 gateway to its gatekeeper. The semantics of existing desired/supported protocol information elements were not appropriate for an H.323 gateway to indicate SIP support to an H.323 gatekeeper. Currently, the best practice for a H.323 gateway (supporting SIP) implementation is to use the h323 information element in the SupportedProtocols choice for this purpose. Agarwal, et al. [Page 29] Internet Draft SIP-H.323 Interworking February 2001 The use of such a field means that this H.323 gateway (supporting SIP) is a pure H.323 proxy, which is not semantically correct. Appendix B gives the modified ASN.1 to show the additions to the H.225 for the support of SIP protocol. 10.2. Call Flows for Basic Configuration H.323 EP ---- IWF ---- SIP EP a) Simple Call from H.323 terminal to SIP terminal. H.323 EP IWF SIP EP User A User B (164.164.28.101) (164.164.28.121) (164.164.28.141) RTP = 2326 RTP = 4346 RTCP = 2327 RTCP = 4347 |Setup(vipin@iwf.sip.com) F1| | |-------------------------->| INVITE F2 | | Call Proc F3 |-------------------------->| |<--------------------------| c=IN IP4 164.164.28.121 | | | m=audio 0 RTP/AVP 0 | | | a=rtpmap:0 PCMU/8000 | | | | | | 100 Trying F4 | | |<--------------------------| | | 180 Ringing F5 | | Alerting F6 |<--------------------------| |<--------------------------| 200 OK F7 | | Connect F8 |<--------------------------| |<--------------------------| c=IN IP4 164.164.28.141 | | | m=audio 4346 RTP/AVP 0 | | | a=rtpmap:0 PCMU/8000 | | TCS F10 | ACK F9 | |-------------------------->|-------------------------->| | TCS Ack F11 | | |<--------------------------| | | TCS F12 | | |<--------------------------| | | TCS Ack F13 | | |-------------------------->| | Agarwal, et al. [Page 30] Internet Draft SIP-H.323 Interworking February 2001 | MSD F14 | | |-------------------------->| | | MSD F14A | | |<--------------------------| | | MSD Ack F15 | | |<--------------------------| | | MSD Ack F16 | | |-------------------------->| | |OLC(RTCP=2327,g711Ulaw) F17| | |-------------------------->| | | OLC Ack(RTP=4326, F18 | | |<--------------------------| | | 164.164.28.141) | | | | | |OLC(RTCP=4347,g711Ulaw) F19| | |<--------------------------| | | | | | OLC Ack(RTP=2326, F20 | | |-------------------------->| INVITE F21 | | 164.164.28.101 |-------------------------->| | | c=IN IP4 164.164.28.101 | | | m=audio 2326 RTP/AVP 0 | | | a=rtpmap:0 PCMU/8000 | | | | | | 200 OK F22 | | |<--------------------------| | | c=IN IP4 164.164.28.141 | | | m=audio 4346 RTP/AVP 0 | | | a=rtpmap:0 PCMU/8000 | | | | | | ACK F23 | | |-------------------------->| | RTCP | 2327 |<=====================================================>| 4347 | RTP | 2326 |<=====================================================>| 4346 This call flow shows the use of a re-INVITE (F20) by the IWF to update the SIP end point SDP. The initial INVITE (F2) contains "dummy" SDP of Agarwal, et al. [Page 31] Internet Draft SIP-H.323 Interworking February 2001 the IWF, since the SDP of the H.323 EP is not yet known. The details of call flow messages are given in Appendix C.1. b) Call from H.323 terminal to SIP terminal using H.245 tunneling. H.323 SIP EP IWF EP User A UserB | Setup(tunn= true,MSD,TCS) F1 | |------------------------->| INVITE F2 | | |-------------------------->| | | 180 Ringing F3 | | Alerting F4 |<--------------------------| |<-------------------------| | | | 200 OK F5 | | Connect(MSD Ack,TCS F6 |<--------------------------| |<-------------------------| | | TCS Ack) | | | | | | Facility(TCS Ack,OLC F7 | | |------------------------->| | | MSD Ack) | | | | | | Facility(OLC Ack,OLC) F8 | | |<-------------------------| | | Facility(OLC Ack) F9 | | |------------------------->| | | | | | | | | | ACK F10 | | |-------------------------->| | RTP | |<====================================================>| This call flow shows the delayed SDP approach, where the initial INVITE (F2) does not contain SDP, but the ACK (F10) does. In this call flow, it is possible that the SIP end point will time out and retransmit the Agarwal, et al. [Page 32] Internet Draft SIP-H.323 Interworking February 2001 200 OK (F5) response, thinking that it had been lost. For simplicity, it is not shown here. The details of call flow messages are given in Appendix C.2. c) Call from H.323 terminal to SIP terminal using early H.245. H.323 SIP EP IWF EP | Setup(H245 Address) | | |------------------------->| INVITE | | |-------------------------->| | H245 Start here | | |<------------------------>| 180 Ringing | | Alerting |<--------------------------| |<-------------------------| 200 OK | | Connect |<--------------------------| |<-------------------------| | | H245 Ends upto this | | |<------------------------>| ACK | | |-------------------------->| | RTP | |<====================================================>| This call flow and message exchanges are very much similar to Section (10.2 a) except that IWF in this case gets the H.245 address of H.323 EP in Setup message. Using this H.245 address and TSAP identifier, IWF opens an H.245 channel with H.323 EP prior to completing Q.931. In this case, all the normal H.245 messages will be exchanged on the seperate H.245 channel but it will be done simultaneously along with Q.931. The ACK on SIP side will be sent only after completing the H.245 message exchange on the H.323 side. d) Call from H.323 terminal to SIP terminal using fast connect procedure. H.323 SIP EP IWF EP Agarwal, et al. [Page 33] Internet Draft SIP-H.323 Interworking February 2001 | Setup(fastStart=true,OLC)| | |------------------------->| INVITE F2 | | F1 |-------------------------->| | | 180 Ringing F3 | | Alerting F4 |<--------------------------| |<-------------------------| 200 OK F5 | | Connect(fastStart=true, |<--------------------------| |<-------------------------| | | OLC) F6 | ACK F7 | | |-------------------------->| | RTP | |<====================================================>| This call flow has the most perfect matching of H.323 message and parameters with SIP message and parameters. Setup from H.323 endpoint will contain the media channel information for forward and reverse channels. This will help in mapping the complete channel information to SDP of SIP INVITE. Similarly, SDP of 200 OK response from SIP side can be easily mapped to open the channels on H.323 side. This call flow will give the immediate availability of media channels from both sides after H.323 Connect and SIP Ack. The details of call flow messages are given in Appendix C.3. e) Call from H.323 terminal to SIP terminal using overlapped sending. H.323 SIP EP IWF EP User A User B | Setup(canOverlapSend= F1 | | |------------------------->| | | true, Incomplete Add.) | | | | | | Setup Ack F2 | | |<-------------------------| INVITE F3 | | |-------------------------->| | | 484 Address Inc. F4 | | |<--------------------------| Agarwal, et al. [Page 34] Internet Draft SIP-H.323 Interworking February 2001 | | ACK F5 | |Information(additional F6 |-------------------------->| |------------------------->| | | address) | INVITE F7 | | |-------------------------->| | | 180 Ringing F8 | | Alerting F9 |<--------------------------| |<-------------------------| 200 OK F10 | | Connect F11 |<--------------------------| |<-------------------------| | | H245 F12 | | |<------------------------>| ACK F13 | | |-------------------------->| | RTP | |<====================================================>| This call flow shows overlapped dialing. On the SIP side, the Call-ID remains the same throughout the flow. The SETUP message contains either: a) no called number information; or b) incomplete called number information; or c) called number information which the network cannot determine to be complete. On receipt of such a SETUP message, the network starts timer T302 (as specified in Q.931), sends a SETUP ACKNOWLEDGE message to the user, and enters the overlap sending state. In case a), the network will return dial tone, if required by the tone option. In this case further address information will be available in the SETUP ACKNOWLEDGE message. When the SETUP ACKNOWLEDGE message is received, the user enters the overlap sending state and optionally starts timer T304 (the value of timer T304 is specified in Q.931 [12]). After receiving the SETUP ACKNOWLEDGE message, the user sends the remainder of the call information (if any) in one or more INFORMATION messages. The called party number information may be provided by the user as follows: a) in the called party number information element; or b) in the keypad facility information element, exclusively. The called party number must be sent in a unique way. Agarwal, et al. [Page 35] Internet Draft SIP-H.323 Interworking February 2001 The details of call flow messages are given in Appendix C.4. g) Call from SIP terminal to H.323 terminal using H.245 tunneling. User B User A SIP H.323 EP IWF EP | INVITE F1 | | |------------------------->| Setup(tunn. =true,TCS,MSD)| | |-------------------------->| | | F2 | | | | | | Alerting(tunn.=true,TCSAck| | |<--------------------------| | 180 Ringing F4 | MSD Ack,TCS) F3 | |<-------------------------| | | |Facility(mess-body=empty, | | |-------------------------->| | |TCS Ack,OLC,MSD Ack) F5 | | | | | |Facility(OLC Ack,OLC) F6 | | |<--------------------------| | |Facility (OLC Ack) F7 | | |-------------------------->| | | Connect F8 | | 200 OK F9 |<--------------------------| |<-------------------------| | | ACK F10 | | |------------------------->| | | RTP | |<====================================================>| The details of call flow messages are given in Appendix C.5. h) Call from SIP terminal to H.323 terminal using early H.245. SIP H.323 EP IWF EP Agarwal, et al. [Page 36] Internet Draft SIP-H.323 Interworking February 2001 | INVITE | | |------------------------->| Setup(h245 Address) | | |-------------------------->| | | Early H245 starts here | | |<------------------------->| | | Alerting | | 180 Ringing |<--------------------------| |<-------------------------| Connect | | |<--------------------------| | | Early H245 ends upto this | | 200 OK |<------------------------->| |<-------------------------| | | ACK | | |------------------------->| | | RTP | |<====================================================>| The call flow diagram for this call is similar to call flow f) except that in this case the H.245 channel was opened immediately after an H.323 endpoint received the H.225 Setup message. i) Call from SIP terminal to H.323 terminal using fast connect procedure. SIP H.323 EP IWF EP | INVITE | | |------------------------->| Setup(fastStart=true,OLC) | | |-------------------------->| | | Alerting | | 180 Ringing |<--------------------------| |<-------------------------|Connect(fastStart=true,OLC)| | 200 OK |<--------------------------| |<-------------------------| | | ACK | | |------------------------->| | | RTP | |<====================================================>| Agarwal, et al. [Page 37] Internet Draft SIP-H.323 Interworking February 2001 This call flow gives a perfect matching of call sequence and parameters. j) Call from SIP terminal to H.323 terminal using overlapped sending. SIP H.323 EP IWF EP User B User A | INVITE F1 | | |------------------------->| Setup(canOverlapSend=true) F2 | |-------------------------->| | 484 Address Incomplete F3| | |<-------------------------| | | ACK F4 | | |------------------------->| Setup Ack. F5 | | |<--------------------------| | | | | INVITE F6 | | |------------------------->| Information(Additional F7 | | |-------------------------->| | | Address) | | | | | | Alerting F8 | | 180 Ringing F9 |<--------------------------| |<-------------------------| Connect F10 | | |<--------------------------| | | H245 F11 | | 200 OK F12 |<------------------------->| |<-------------------------| | | ACK F13 | | |------------------------->| | | RTP | |<====================================================>| This call flow shows overlapped dialing. On the SIP side, the Call-ID remains the same throughout the flow. The details of call flow messages are given in Appendix C.6. Agarwal, et al. [Page 38] Internet Draft SIP-H.323 Interworking February 2001 10.3 Calls using both H.323 GK and SIP Server H.323 EP ---- H.323 GK ---- IWF ---- SIP Server ---- SIP EP Assumption: GK routes the call up to Q.931 signaling only. This section only gives the details of call sequence. Message details are similar and can be derived from the details of Section 10.2. a) Simple Call from H.323 terminal to SIP terminal. (i) With SIP Proxy H.323 H.323 SIP SIP EP GK IWF Proxy EP | ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | | Setup | | | | |------------>| Setup | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| INVITE | | | | |------------>| INVITE | | | | |------------>| | | | | 180 Ringing | | | | 180 Ringing |<------------| | | Alerting |<------------| | | Alerting |<------------| | | |<------------| | | 200 OK | | | | 200 OK |<------------| | | Connect |<------------| | | Connect |<------------| | | |<------------| | | | | H.245 | | | Agarwal, et al. [Page 39] Internet Draft SIP-H.323 Interworking February 2001 |<------------------------->| ACK | | | | |------------>| ACK | | | | |------------>| | | | | | | | RTP | | |<=====================================================>| (ii) With SIP Redirect H.323 H.323 SIP SIP EP GK IWF Redirect EP | ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | | Setup | | | | |------------>| Setup | | | | |----------->| | | | | ARQ | | | | |<-----------| | | | | ACF | | | | |----------->| INVITE | | | | |----------->| | | | | 302 Moved | | | | |<-----------| | | | | ACK | | | | |----------->| | | | | INVITE | | | |-------------------------->| | | | 180 Ringing | | | Alerting |<--------------------------| | Alerting |<-----------| | |<------------| | 200 OK | | | Connect |<--------------------------| | Connect |<-----------| | |<------------| | | | H.245 | | |<------------------------>| ACK | | |-------------------------->| | RTP | Agarwal, et al. [Page 40] Internet Draft SIP-H.323 Interworking February 2001 |<====================================================>| This call flow shows the message sequence in case of H.323 GK and SIP Server. Details of messages are similar to other call flows explained above. b) Call from H.323 terminal to SIP terminal using H.245 tunneling. H.323 H.323 SIP SIP EP GK IWF Proxy EP | ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | |Setup(tunn= | | | | |------------>| ARQ | | | |true,TCS,MSD)|----------->| | | | | ACF | | | | |<-----------| | | | |Setup(tunn= | | | | |----------->| INVITE | | | |true,TCS,MSD|----------->| INVITE | | | | |------------->| | | | | 180 Ringing | | | |180 Ringing |<-------------| | |Alerting(MSD|<-----------| | |Alerting(MSD |<-----------| | | |<------------|Ack,TCS Ack,| | 200 OK | |Ack,TCS Ack, |TCS) | 200 OK |<-------------| |TCS) | |<-----------| | | | | | | |Facility(OLC)| | | | |------------>|Facility(OLC| | | | |----------->| | | | | | | | | |Facility(OLC| | | |Facility(OLC |<-----------| | | |<------------|Ack,OLC) | | | |Ack,OLC) | | | | Agarwal, et al. [Page 41] Internet Draft SIP-H.323 Interworking February 2001 | | | | | |Facility(OLC | | | | |------------>|Facility(OLC| | | | Ack) |----------->| | | | | Ack) | | | | | | | | | | Connect | | | | Connect |<-----------| | | |<------------| | | | | H245 | | | |<------------------------>| ACK | | | | |----------->| ACK | | | | |------------->| | RTP | | |<====================================================>| In this call scenario, it takes too much time between "200 OK" and "ACK". The other approach can be to send the ACK immediately and then resend a "INVITE" after completing H.245 message exchange. c) Call from H.323 terminal to SIP terminal using early H.245. c) Call from H.323 terminal to SIP terminal using early H.245. H.323 H.323 SIP SIP EP GK IWF Proxy EP | ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | |Setup(H245 | | | | |------------>| ARQ | | | | Address) |------------>| | | | | ACF | | | | |<------------| | | | | Setup(H245 | | | | |------------>| INVITE | | | | Address) |------------>| INVITE | | H245 Starts here | |------------>| Agarwal, et al. [Page 42] Internet Draft SIP-H.323 Interworking February 2001 |<------------------------->| | 180 Ringing | | | 180 Ringing |<------------| | | Alerting |<------------| 200 OK | | Alerting |<------------| 200 OK |<------------| |<------------| Connect |<------------| | | Connect |<------------| | | |<------------| | | | | H245 Ends upto this | | | |<------------------------->| ACK | | | | |------------>| ACK | | | | |------------>| | | RTP | | |<====================================================>| d) Call from H.323 terminal to SIP terminal using fast connect procedure. H.323 H.323 SIP SIP EP GK IWF Proxy EP | ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | |Setup(fast | | | | |------------>| ARQ | | | |Conn,OLC) |------------>| | | | | ACF | | | | |<------------| | | | |Setup(fast | | | | |------------>| INVITE | | | |Conn,OLC) |------------>| INVITE | | | | |------------>| | | | | 180 Ringing | | | | 180 Ringing |<------------| | | Alerting |<------------| 200 OK | | Alerting |<------------| 200 OK |<------------| |<------------| Connect |<------------| | | Connect |<------------| | | Agarwal, et al. [Page 43] Internet Draft SIP-H.323 Interworking February 2001 |<------------| | | | | H245 | | | |<------------------------->| ACK | | | | |------------>| ACK | | | | |------------>| | | RTP | | |<=====================================================>| e) Call from H.323 terminal to SIP terminal using overlapped sending. H.323 H.323 SIP SIP EP GK IWF Proxy EP |ARQ(Incomp. | | | | |------------>| | | | | Address) | | | | | | | | | |ARJ(rejectRea| | | | |<------------| | | | |son=Incomp. | | | | | Address) | | | | | | | | | |ARQ(Addition | | | | |------------>| | | | |al Address) | | | | | | | | | | ACF | | | | |<------------| | | | | Setup | | | | |------------>| Setup | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| INVITE | | | | |------------>| INVITE | | | | |------------>| | | | | 180 Ringing | Agarwal, et al. [Page 44] Internet Draft SIP-H.323 Interworking February 2001 | | | 180 Ringing |<------------| | | Alerting |<------------| | | Alerting |<------------| | | |<------------| | | 200 OK | | | | 200 OK |<------------| | | Connect |<------------| | | Connect |<------------| | | |<------------| | | | | H.245 | | | |<------------------------->| ACK | | | | |------------>| ACK | | | | |------------>| | | | | | | | RTP | | |<=====================================================>| f) Simple call from SIP terminal to H.323 terminal. (i) With SIP Proxy SIP SIP H.323 H.323 EP Proxy IWF GK EP | | | | | | INVITE | | | | |------------>| INVITE | | | | |------------>| ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | | Setup | | | | |------------>| Setup | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| | | | | Alerting | | | | Alerting |<------------| | | 180 Ringing |<------------| | Agarwal, et al. [Page 45] Internet Draft SIP-H.323 Interworking February 2001 | 180 Ringing |<------------| | | |<------------| | | Connect | | | | Connect |<------------| | | |<------------| | | | | H.245 | | | 200 OK |<------------------------->| | 200 OK |<------------| | | |<------------| | | | | ACK | | | | |------------>| ACK | | | | |------------>| | | | | RTP | | |<=====================================================>| (ii) With SIP Redirect SIP SIP H.323 H.323 EP Redirect IWF GK EP | INVITE | | | | |------------>| | | | | 302 Moved | | | | |<------------| | | | | ACK | | | | |------------>| | | | | INVITE | | | |-------------------------->| ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | | Setup | | | | |------------>| Setup | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| | | | | Alerting | | | | Alerting |<------------| | |180 Ringing |<------------| | Agarwal, et al. [Page 46] Internet Draft SIP-H.323 Interworking February 2001 |180 Ringing |<------------| | | |<------------| | | Connect | | | | Connect |<------------| | | |<------------| | | | | H.245 | | 200 OK |<------------------------->| |<--------------------------| | | | ACK | | | |-------------------------->| | | | | RTP | | |<=====================================================>| g) Call from SIP terminal to H.323 terminal using H.245 tunneling. SIP SIP H.323 H.323 EP Proxy IWF GK EP | | | | | | INVITE | | | | |------------>| INVITE | | | | |------------>|Setup(tunn.= | | | | |true,MSD,TCS)| | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| Setup(MSD, | | | | | TCS) | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| | | | |Alerting(MSD | | | | |Ack,TCS Ack, | | | | |TCS,MSD) | | | |Alerting(MSD |<------------| | | |Ack,TCS Ack, | | | | |TCS,MSD) | | | | 180 Ringing |<------------| | Agarwal, et al. [Page 47] Internet Draft SIP-H.323 Interworking February 2001 | 180 Ringing |<------------| | | |<------------| |Facility(TCS | | | | |Ack,MSD Ack, | | | | |OLC) | | | | |------------>|Facility(TCS | | | | |Ack,MSD Ack, | | | | |OLC) | | | | |------------>| | | | |Facility(OLC | | | | |Ack,OLC) | | | |Facility(OLC |<------------| | | |Ack,OLC) | | | | |<------------| | | | |Facility(OLC | | | | |Ack) | | | | |------------>|Facility(OLC | | | | |Ack) | | | | |------------>| | | | | Connect | | | | Connect |<------------| | | 200 OK |<------------| | | 200 OK |<------------| | | |<------------| | | | | ACK | | | | |------------>| ACK | | | | |------------>| | | | | RTP | | |<=====================================================>| h) Call from SIP terminal to H.323 terminal using early H.245. SIP SIP H.323 H.323 EP Proxy IWF GK EP | | | | | | INVITE | | | | |------------>| INVITE | | | | |------------>|Setup(H245 | | | | |------------>|Setup(H245 | | | |Address) |------------>| | | | | Address) Agarwal, et al. [Page 48] Internet Draft SIP-H.323 Interworking February 2001 | | | H245 starts here | | | |<------------------------->| | | | | Alerting | | | | Alerting |<------------| | | 180 Ringing |<------------| Connect | | 180 Ringing |<------------| Connect |<------------| |<------------| |<------------| | | | | H245 ends up to this | | | 200 OK |<------------------------->| | 200 OK |<------------| | | |<------------| | | | | ACK | | | | |------------>| ACK | | | | |------------>| | | | | RTP | | |<=====================================================>| i) Call from SIP terminal to H.323 terminal using fast connect procedure. SIP SIP H.323 H.323 EP Proxy IWF GK EP | | | | | | | | | | | INVITE | | | | |------------>| INVITE | | | | |------------>| ARQ | | | | |------------>| | | | | ACF | | | | |<------------| | | | | Setup(with | | | | | fast start | | | | | and OLC) | | | | |------------>| Setup(with | Agarwal, et al. [Page 49] Internet Draft SIP-H.323 Interworking February 2001 | | | | fast start | | | | | and OLC) | | | | |------------>| | | | | ARQ | | | | |<------------| | | | | ACF | | | | |------------>| | | | |Alerting(with| | | | |fast start) | | | |Alerting(with|<------------| | | |fast start) | | | | 180 Ringing |<------------| | | 180 Ringing |<------------| | | |<------------| | |Connect(with | | | | |fast start | | | | |and OLC) | | | |Connect(with |<------------| | | |fast start | | | | |and OLC) | | | | 200 OK |<------------| | | 200 OK |<------------| | | |<------------| | | | | ACK | | | | |------------>| ACK | | | | |------------>| | | | | RTP | | |<=====================================================>| 11. State Machine: This section defines the state machine for a basic call. The state machine for complex calls will be defined in next release of this draft. (This is a draft proposal and will be refined as more analysis will be done for all call scenarios.) This section includes only those RAS messages which are defined for H.323 terminal/gateway in Section 7.7 Table 19/H.225 [12]. This section includes only those Q.931 messages which are defined for a H.323 terminal/gateway in Section 7.1/H.225 [12]. This section includes only Agarwal, et al. [Page 50] Internet Draft SIP-H.323 Interworking February 2001 a partial list of H.245 messages, which may be required for a basic call. This section includes only a partial list of SIP messages, which may be required for a basic call. This section use the Timers defined in SIP[3], H.225 [12] and Table 9-1/Q.931 [14]. Only messages related to a call are listed as possible messages/events. All other non call related messages like RRQ, Register will not be handled by the call state machine and these messages will be treated as pre call messages. The behavior of the IWF and handling of these messages are explained in Section 10.1 11.1 State machine (SIP to H.323) ----------------------------------- +-------------------------+ +---------------->+ Idle +<------------+ | +---+---------------+-----+ | | | | | | | INVITE/ARQ | | | V | | | ARJ +-----------------+ | | +<----------+ WaitForAdm | | INVITE(PreGranted | | +---------+-------+ | ARQ or GK | | | ACF/Setup | not present)/ | | V V Setup | | T303 +-------------------------+ RLC | +<----------------+ WaitForAlerting +------------>+ | +---+--------+------+-----+ | | Call Proc./ | ^ | | | | 100 Trying | | | | | | +--+ | | | | | | Connect/ | | | | 180 Ringing | | | | | | Alerting/ | | | | 180 Ringing | | | | V V | | T301 +-------------------------+ RLC | +<----------------+ WaitForH245Complete +------------>+ | +---+--------+------------+ | Agarwal, et al. [Page 51] Internet Draft SIP-H.323 Interworking February 2001 | | ^ | | | Connect | | | | | +---+ | H245Complete/ | | | 200 OK | | | | | V | | BYE +-------------------------+ RLC | +<----------------+ Connected +------------>+ +-------------------------+ Figure 2: State machine for SIP to H.323 call. 11.2 SIP-H.323 State Machine Behavior For Various Events -------------------------------------------------------- State : Idle Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- RAC Non Triggering Sec.11.2.1 Sec.11.2.1 INVITE Triggering Sec.11.2.2 Sec.11.2.2 All unexpected messages in this state will cause an error indication. All other messages will be either Non Triggering or for further study. 11.2.1 RAC: If this RAC is for the previous RAI (almostOutOfResources = true) then do not accept new calls. If this RAC is for a previous RAI having almostOutOfResources = false, then accept new calls. The RAI action will be taken by H.323 GK for calls coming from H.323 network. 11.2.2 INVITE: 100 Trying SHALL be sent immediately after receiving INVITE. (i) If a INVITE message is received in "Idle" state, then send ARQ to H.323 GK (if it is present in the network, i.e. IWF is registered to a H.323 GK). Agarwal, et al. [Page 52] Internet Draft SIP-H.323 Interworking February 2001 Next State: WaitForAdm (Waiting For Admission) (ii)If IWF has a preGranted ARQ or if no H.323 GK is present in network (i.e.IWF is not registered with any H.323 GK), then send H.225 Setup message. Setup is sent when the IWF can resolve the IP Address to which the message has to be sent, e.g., when it has pregranted ARQ, or the SIP URI gives the H.323 host name. This MAY involve H.323 LRQ/LCF messages, but does not alter the state of the call. If the H.323 IP address is not known or can not be resolved then IWF sends back 404 Not Found. Next State: WaitForAlerting State : WaitForAdm (Waiting For Admission) Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- ACF Triggering Send Setup, WaitForAlerting ARJ Triggering Send 4xx Idle DRQ Non Triggering Send 4xx,Send DCF Idle RAC Non Triggering See 11.2.1 State : WaitForAlerting (Waiting For Alerting) Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- DRQ Non Triggering Send 4xx,Send DCF, Idle Send RLC. RAC Non Triggering See 11.2.1 SetupAcknowledge Non Triggering Sec.11.2.3 See 11.2.3 CallProceeding Non Triggering Send 100 Trying Alerting Triggering Send 180 Ringing WaitForH245Complete Connect Triggering Send 180 Ringing WaitForH245Complete ReleaseComplete Triggering Send 4xx,Send DRQ Idle T303(first exp.) Non Triggering Send Setup T303(second exp.) Triggering Send4xx,Send RLC Idle TCS See 11.2.4 See 11.2.4 TCS Ack See 11.2.4 See 11.2.4 Agarwal, et al. [Page 53] Internet Draft SIP-H.323 Interworking February 2001 MSD See 11.2.4 See 11.2.4 MSD Ack See 11.2.4 See 11.2.4 OLC See 11.2.4 See 11.2.4 OLC Ack See 11.2.4 See 11.2.4 UserInputInd See 11.2.4 See 11.2.4 EndSession See 11.2.4 See 11.2.4 INVITE FFS FFS CANCEL Triggering Send 4xx,Send DRQ Idle 11.2.3 If a SetupAcknowledge is received by an IWF from H.323 network after sending Setup message, then additional addressing information should be sent using INFORMATION messages. If the address is incomplete and the canOverlapSend field set to FALSE, the call should be dropped using RELEASE COMPLETE. 11.2.4 If the Setup message contains the fastStart or tunnelled H.245 messages, then all H.245 messages will be handled normally according to H.245 call handling procedures. It MAY be needed to open a H.245 channel between the IWF and the H.323 terminal/Gatekeeper. H245Complete event is initiated when the media channels between the caller and callee are open in both directions. When H.245 is complete, 200 OK SHALL be sent to SIP network. State : WaitForH245Complete (Waiting For H.245 Complete) Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- DRQ Non Triggering Send 4xx,Send DCF Idle Send RLC. RAC Non Triggering See 11.2.1 Connect Non Triggering No action req. ReleaseComplete Triggering Send 4xx,Send DRQ Idle T301 Triggering Send 4xx,Send RLC TCS See 11.2.4 See 11.2.4 TCS Ack See 11.2.4 See 11.2.4 MSD See 11.2.4 See 11.2.4 MSD Ack See 11.2.4 See 11.2.4 Agarwal, et al. [Page 54] Internet Draft SIP-H.323 Interworking February 2001 OLC See 11.2.4 See 11.2.4 OLC Ack See 11.2.4 See 11.2.4 UserInputInd See 11.2.4 See 11.2.4 EndSession See 11.2.4 See 11.2.4 H245 Complete Triggering See 11.2.4 CallConnected INVITE FFS FFS CANCEL Triggering Send 4xx,Send DRQ Idle State : CallConnected (Call Connected) Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- DRQ Non Triggering Send 4xx,Send DCF Idle Send RLC RAC Non Triggering See 11.2.1 ReleaseComplete Triggering Send 4xx,Send DRQ Idle TCS See 11.2.4 See 11.2.4 TCS Ack See 11.2.4 See 11.2.4 MSD See 11.2.4 See 11.2.4 MSD Ack See 11.2.4 See 11.2.4 OLC See 11.2.4 See 11.2.4 OLC Ack See 11.2.4 See 11.2.4 UserInputInd See 11.2.4 See 11.2.4 EndSession See 11.2.4 See 11.2.4 INVITE FFS FFS CANCEL Triggering Send 4xx,Send DRQ Idle 11.3 State Machine (H323 to SIP) -------------------------------- +-------------------------+ +---------------->+ Idle +<------------+ | +---+---------------+-----+ | | | | | | | Setup/ARQ | | | V | | | ARJ/RLC +-----------------+ | | +<----------+ WaitForAdm | | Setup/INVITE | Agarwal, et al. [Page 55] Internet Draft SIP-H.323 Interworking February 2001 | +---------+-------+ | (Pregranted ARQ | | | ACF/INVITE | or GK not | | | | present) | | | | | | | 100 Trying/ | | | | Call Proc. | | | | +-------+ | | | | | | | | | V | V V | | CANCEL +------+------------------+ RLC | +<----------------+ WaitForRinging +------------>| | +-------------------------+ | | | | | | |180 Ringing/ | 200 OK/ | | | Alerting | Connect | | V V | | BYE or CANCEL+--------------------------+ RLC | +<----------------+ WaitForChannelsConnected +----------->+ | +---+--------+-------------+ | | | ^ | | | 200 OK/Connect| | | | | +---+ | H245Complete/ | | |ACK | | | | | V | | BYE +-------------------------+ RLC | +<----------------+ CallConnected +------------>+ +-------------------------+ Figure 3: State machine for H.323 to SIP call. 11.4 H.323-SIP State Machine Behavior For Various Events ------------------------------------------- Agarwal, et al. [Page 56] Internet Draft SIP-H.323 Interworking February 2001 State : Idle Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- RAC Non Triggering Sec.11.2.1 Sec.11.2.1 Setup Triggering Sec.11.4.1 Sec.11.4.1 11.4.1 Setup: IWF SHALL send the Call Proceeding message immediately after receiving Setup message. (i) If a Setup message is received in "Idle" state, then send ARQ to H.323 GK (if it is present in the network, i.e. IWF is registered to a H.323 GK). Next State: WaitForAdm (Waiting For Admission) (ii)If IWF has a preGranted ARQ or if no H.323 GK is present in network (i.e.IWF is not registered with any H.323 GK), then send INVITE message. Next State: WaitForRinging 11.4.2 The Setup message will contains the fastStart or tunnelled H.245 messages, all H.245 messages will be handled normally according to H.245 call handling procedures. It MAY be needed to open a H.245 channel between the IWF and the H.323 terminal/Gatekeeper. H245Complete event is initiated when the media channels between the caller and callee are open in both directions. When H.245 is complete, ACK SHALL be sent to SIP network. State : WaitForAdm (Waiting For Admission) Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- ACF Triggering Send INVITE WaitForRinging ARJ Triggering Send RelComp Idle RAC Non Triggering Sec.11.2.1 Sec.11.2.1 ReleaseComplete Triggering Send DRQ, CANCEL Idle Agarwal, et al. [Page 57] Internet Draft SIP-H.323 Interworking February 2001 State : WaitForRinging Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- BRQ FFS FFS RAC Non Triggering Sec.11.2.1 Sec.11.2.1 DRQ Triggering Send DCF,CANCEL,RLC Idle ReleaseComplete Triggering Send DRQ, CANCEL Idle TCS See 11.4.2 See 11.4.2 TCS Ack See 11.4.2 See 11.4.2 MSD See 11.4.2 See 11.4.2 MSD Ack See 11.4.2 See 11.4.2 OLC See 11.4.2 See 11.4.2 OLC Ack See 11.4.2 See 11.4.2 UserInputInd See 11.4.2 See 11.4.2 EndSession See 11.4.2 See 11.4.2 100 Trying Non Triggering Send CallProc. 180 Ringing Triggering Send Alerting WaitFor Channels Connected 200 OK Triggering Send Connect WaitFor Channels Connected BYE Triggering Send DRQ,RLC Idle State : WaitForChannelsConnected Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- BRQ FFS FFS RAC Non Triggering Sec.11.2.1 Sec.11.2.1 DRQ Triggering Send DCF,RLC Idle Send BYE/CANCEL ReleaseComplete Triggering Send DRQ Idle Send BYE/CANCEL TCS See 11.4.2 See 11.4.2 TCS Ack See 11.4.2 See 11.4.2 MSD See 11.4.2 See 11.4.2 MSD Ack See 11.4.2 See 11.4.2 OLC See 11.4.2 See 11.4.2 Agarwal, et al. [Page 58] Internet Draft SIP-H.323 Interworking February 2001 OLC Ack See 11.4.2 See 11.4.2 UserInputInd See 11.4.2 See 11.4.2 EndSession See 11.4.2 See 11.4.2 H245 Complete Triggering Send ACK CallConnected 200 OK Triggering Send Connect BYE Triggering Send DRQ,RLC Idle State : CallConnected Possible Messages Message Category Action Next state ----------------- ---------------- ---------- ---------- BRQ FFS FFS RAC Non Triggering Sec.11.2.1 Sec.11.2.1 DRQ Triggering Send DCF,BYE,RLC Idle ReleaseComplete Triggering Send DRQ,BYE Idle TCS See 11.4.2 See 11.4.2 TCS Ack See 11.4.2 See 11.4.2 MSD See 11.4.2 See 11.4.2 MSD Ack See 11.4.2 See 11.4.2 OLC See 11.4.2 See 11.4.2 OLC Ack See 11.4.2 See 11.4.2 UserInputInd See 11.4.2 See 11.4.2 EndSession See 11.4.2 See 11.4.2 H245 Complete Triggering Send ACK CallConnected BYE Triggering Send DRQ,RLC Idle 12. Implementation Requirements * Terminal Number for the SIP-H323 IWF for H.323 master-slave (MS) determination SHALL be Gateway without MC. * DTMF on H323 side SHALL be carried by User Input Indication. Since there is no media processing in IWF, so the DTMF carried in RTP streams (like in MicroSoft's Netmeeting) SHALL not be transferred to the SIP side. DTMF on SIP side MAY be carried by SIP INFO method. Agarwal, et al. [Page 59] Internet Draft SIP-H.323 Interworking February 2001 * The gateway MAY replicate DTMF digits (received from the SIP network) via H.245 UserInputIndications. No DTMF timing information is sent with H.245v2 UserInputIndications. Therefore, we MAY need to use default DTMF time and inter digit timing definitions for future versions to insure that DTMF digits are properly played out into the SIP network. * An alternative method of sending DTMF (besides UserInputIndications) is via a separate RTP stream using the IETF draft(draft-ietf-avt-dtmf- 00.txt). If when finalized, this draft meets with the VoIP forums approval, then it will be specified as an optional method that endpoints MAY use for DTMF carriage. * Some Call flow examples shows a delayed "ACK" on SIP side. In practical cases, this MAY trigger a timeout on SIP side. In these cases, SIP reinvite will be used and ACK will be sent immediately after getting 200 OK. * Re-invite will be used when necessary. However, the use of reinvite will be avoided because the SIP endpoint MAY not support it. * IWF will contain a look up table which may be used for address resolution in cases when H.323 GK or SIP Server doesn't exist in the network. This lookup table MAY also be used in conjunction with H.323 GK and/or SIP Server. * Registration messages in most of the cases for the H.323 and SIP system will be limited to their domain only. IWF in this case will be a part of both SIP and H.323 domain. This strategy will help in keeping a distributed data for address resolution. This will also help in making a scalable solution. This will be discussed in more detail in Phase 2. * Set the Destination information in H.323 Call Proceeding and Alerting as "gateway" to specify that the call is routed through IWF. * mediaWaitForConnect in H.323 Setup will be set to "false" unless the endpoint is ready for receiving media immediately or if there is a mechanism to buffer the media traffic. * callType for basic calls in H.323 Setup will be set to "pointTopoint". Agarwal, et al. [Page 60] Internet Draft SIP-H.323 Interworking February 2001 * Set the mc=FALSE and undefinedNode=FALSE in the registration message to H.323 network. * The IWF SHOULD support the Q.931 messages listed in Table 3. An entry of "not applicable" in the table means that it is not visible to the SIP endpoint and is only local to the IWF's H.323 stack. Message IWF sends to H.323 H.323 sends to IWF ________________________________________________________ Alerting Supported Supported Call proceeding Supported Supported Connect Supported Supported Progress Not applicable Not applicable Setup Supported Supported Setup Ack Supported Not applicable Release Complete Supported Supported User Information Not applicable Not applicable Information Supported Supported Notify Not applicable Not applicable Status Not applicable Not applicable Status Inquiry Not applicable Not applicable Facility Supported Supported Table 3: Support for Q.931 messages The IWF MUST NOT close the call signaling channel after the call is established. However, if the call is routed through a gatekeeper and the gatekeeper closes the call signaling channel, the IWF MUST comply with H.323 and MUST NOT assume that the call is closed as long as H.245 channel is open. If the Q.931 TCP connection is closed without closing the call signaling channel, then the IWF SHOULD try reopening the TCP connection, as specified by H.323. In case of failure such as TCP connection refused or TCP connection timeout, the IWF SHOULD close the call on the SIP side also by sending a BYE. Q.931-specific information elements, other than user-user information element (UUIE), do not affect the operation of this IWF, however they are required for interoperation with other H.323 Agarwal, et al. [Page 61] Internet Draft SIP-H.323 Interworking February 2001 entities. The specific fields of UUIE used in translating to SIP message are given in Section . Bearer Capability: Information transfer capability (octet 3, bits 0--5): Unless some other restrictions apply (e.g., the IWF is connected to a bandwidth-restricted ISDN network), the parameter SHOULD be set to "unrestricted digital information" or "restricted digital information" on outgoing side. If the IWF knows that the call is going to be voice only, it may choose to set it as "speech" or "3.1 kHz Audio". The IWF ignores this field on incoming requests. Information Transfer Rate and Rate multiplier: If bandwidth information is available from the gatekeeper or some external means (e.g., from bandwidth information in SDP message), then information transfer rate and rate multiplier may be set to values reflecting the bandwidth, else they should be set to some high value as appropriate. This way the bandwidth is not limited to 64 kb/s or 128 kb/s. On the incoming side these values SHOULD be ignored. Note that in Q.931 message the only possible values are multiples of 64 kb/s. Layer 1 protocol (octet 5, bits 1--5): For outgoing Q.931 messages, the parameter is set to H.221 ('00101'), indicating an H.323 video phone call, unless the IWF knows that the call is going to be voice only (e.g., if this is hardcoded in the IWF). In that case, it may encode the parameter as G.711 A-law or mu-law to indicate this. For incoming Q.931 messages, the IWF ignores this field. Calling or Called party number: For outgoing Q.931 messages, the IWF translates the SIP request-URI into an e164 number, as described in Section 6. The Agarwal, et al. [Page 62] Internet Draft SIP-H.323 Interworking February 2001 calling/called party subaddress is not included in Q.931 messages originating from the IWF. For incoming Q.931 messages, the IWF relies on user-user information element for addresses e.g., sourceAddress and destinationAddress fields of UUIE) and ignores the Q.931 parameter. However, if the calling/called party number is present and e164-ID is not present in the H.323 Alias Address then the calling/called party number is used instead of e164-ID while translating address in section 8. H.323 specifies that the called and calling party Subaddress fields are needed for some circuit switched call scenarios and they SHOULD NOT be used for packet based network side only calls. Display: For incoming Q.931 messages, the IWF MAY copy the Display IE to the display parameter of the SIP To header field.Similarly, for outgoing Q.931 messages, the Display parameter MAY be copied from the display parameter of the SIP To field. Cause: For incoming Q.931 messages, the Q.931 Cause information element and/or the UUIE reason field are mapped to the appropriate SIP status response code, as described in Table 1. H.225.0 [12] specifies that either the Cause information element or the releaseCompleteReason MUST be present. It also gives a mapping between the Cause information element and the releaseCompleteReason. Table 1 gives the mapping between releaseCompleteReason and the appropriate SIP status response. Similarly, for outgoing Q.931 messages, the Q.931 Cause information element and the UUIE reason field are derived according to Table 1. User-User-Information-Element: Below, we detail the fields in UUIE which are relevant to H.323-SIP conversion. Other fields are interpreted as defined by H.225.0. Agarwal, et al. [Page 63] Internet Draft SIP-H.323 Interworking February 2001 sourceInfo/destinationInfo: In all messages from the IWF, this field SHOULD be set to indicate that this endpoint is a gateway. However, the sequence of supported protocols in "GatewayInfo" may be empty. H.245SecurityMode, tokens, cryptoTokens: These fields are interpreted as in H.323. Note that since H.245 is terminated at the IWF, this kind of security information is not relevant to the SIP cloud. (Security issues will be addressed in the next phase.) fastStart: FastStart PDUs contain the OpenLogicalChannel (OLC) messages. The IWF converts incoming OLC messages to a SDP message body. One SDP media description line ("m=") is generated for each distinct session-ID. All logical channels with same session-ID appear as payload types in a single SDP media description line. When converting SIP to H.323, the SDP message is converted to a list of OpenLogicalChannel messages, one per payload type. H.323 endpoint will select atmost one OLC per session-ID. This selected OLC is returned by the H.323 endpoint in the fastStart field of Q.931 Connect message. When converting H.323 to SIP, each OLC in fastStart corresponds to a payload type of SDP. All the OLC messages with same session-ID form a single media description ("m=") line. The parameters for the Q.931 SETUP message are listed below. sourceAddress: Converted to/from SIP header From field as described in section 8. destinationAddress: Converted to/from SIP header To field as described in section 8. Agarwal, et al. [Page 64] Internet Draft SIP-H.323 Interworking February 2001 destCallSignalAddress: If the To SIP header field contains a numeric host identifier then destCallSignalAddress is set to the IPv4 address represented by the numeric identifier. conferenceGoal: Set to "create" in outgoing Q.931 messages. (Additional values may be supported in future versions of this specification that support conferencing.) remoteExtensionAddress: Not present in outgoing Q.931 messages. For incoming Q.931 messages, this parameter is combined with the DestinationAddress parameter to generate the SIP To header field and the request-URI. mediaWaitForConnect: Set to "false" in outgoing Q.931 messages. Ignored in incoming Q.931 messages, as media transmission is transparent to the IWF. Table 4 details how an IWF handles H.245 messages. An entry of "not applicable" means that the message does not affect the behavior within the SIP cloud. The remainder of this subsection lists the possible values of some of the fields of H.245 messages. Refer to H.245 version 3.0 for description and details of the ASN.1 structures for H.245. MasterSlaveDetermination: The terminalType parameter is set to indicate that this terminal is a gateway. H.323 specifies a set of numerical values of terminalType for different types of terminals. For example, a gateway without a multipoint controller (MC) has a terminalType of 60; A gateway with a MC and no multipoint processor (MP) has a terminalType value of 80. Other values of terminalType are not relevant to this IWF in the case where media traffic is transparent. See H.323 [5] for other possible values of terminalType. Agarwal, et al. [Page 65] Internet Draft SIP-H.323 Interworking February 2001 Message REQUIRED or Not applicable MasterSlaveDetermination/Ack/Rej/Rel Not Applicable TerminalCapSet/Ack/Reject/Release REQUIRED Send TerminalCapabilitySet Not Applicable OpenLogicalChannel/Ack/Reject REQUIRED OpenLogicalChannelConfirm Not Applicable CloseLogicalChannel/Ack REQUIRED RequestChannelClose OPTIONAL RequestMode/Ack/Rej/Rel RECOMMENDED RoundTripDelayReq/Res Not applicable MaintenanceLoopReq/Ack/Reject Not supported MaintenanceLoopOffCmd Not supported CommunicationModeReq/Res/Cmd For further study ConferenceReq/Res/Cmd/Indic For further study EndSessionCommand REQUIRED FlowControlCommand For further study Encryption Command For further study Jitter Indication For further study User Input REQUIRED H2250MaxSkewIndic For further study MClocationIndication For further study FunctionNotUnderstood Not Applicable FunctionNotSupported Not Applicable vendorIdentifier Not Applicable MiscCommand/Indication For further study Table 4: Support for H.245 messages. An entry of "not applicable" means that it is not visible to the SIP endpoint and is only local to the IWF's H.323 stack. TerminalCapabilitySet: multiplexCapability::h2250Capability: maximumAudioDelayJitter should be set to maximum possible value as specified by H.323. MultipointCapabilities should reflect minimum capability of Centralized Control/ Audio/ Video/ Data. Other conferencing Agarwal, et al. [Page 66] Internet Draft SIP-H.323 Interworking February 2001 capabilities are for further study. RTCP videoControlCapability should be set to false because anyway H.245 indications have to be used for this purpose. MediaPacketizationCapability should contain the information about the dynamic payload types used by SIP endpoint. Transport Capability should be absent. redundancyEncodingCapability should be absent. This is not supported in this version. logicalChannelSwitchingCapability may be supported by the IWF's H.323 stack. This makes mapping SIP re- INVITE easier. t120DynamicPortCapability is set to false because T120 data is not supported in this version. CapabilityTableEntry and CapabilityDescriptor are mapped from the session description given by SDP. A single capability descriptor is used in H.245. All the payload types on a single media description line (m=) are combined to form an alternative capability set in H.245. All such media description lines are combined to form a simultaneous capability set (or a capability descriptor). Mapping multiple SDP received in multipart body of SIP to multiple capability descriptor is for further study. Capability: H233Encryption is not applicable. H235Security is not applicable. DataApplication capability is not supported in this version of the specification. ConferenceCapability is for further study and is not supported in this version of the specification. UserInputCapability may be supported by the IWF. This is Agarwal, et al. [Page 67] Internet Draft SIP-H.323 Interworking February 2001 used to convey DTMF digits. Use of the SIP INFO method may be considered for this purpose. maxPendingReplacementFor is not applicable. Audio and Video: A capability in H.323 represents a payload type. Refer to http://www.iana.org/assignments/media-types/media- types for a list of MIME types and http://www.iana.org/assignments/rtp-parameters for a list of static RTP payload types. Use of static RTP payload types in SDP is discouraged. The IWF should maintain a list of all currently available payload types and media formats and the corresponding RFC numbers. (An intelligent IWF MAY periodically download and parse these HTML pages to update its database). The predefined audio and video capabilities are mapped to appropriate media format and RTP payload type. This mapping is given in this document for ease of reference. This mapping should be used by the IWF to convert the H.323 capability to an SDP media description. When converting from H.323 to SDP, the IWF SHOULD use dynamic payload type. When converting from SDP to H.323, the IWF SHOULD NOT use dynamic payload types because many current implementations do not support these. However, the IWF MUST be able to receive dynamic payload types, in both H2250Capability.MediaPacketizationCapabilty.RTPPayload Type and in H250LogicalChannelParameters.MediaPacketization. When dynamic RTP payload type are used, H225LogicalChannelParameters.dynamicRTPPayloadType MUST match the payload type description given in mediaPacketization. 13. Activities Planned for Next Phase Agarwal, et al. [Page 68] Internet Draft SIP-H.323 Interworking February 2001 13.1 Simple call supplementary services like call forwarding, call hold and call transfer. 13.2 Conferencing. 13.3 Session change (re-invite, mode request). 13.4 Security 13.5 QOS signalling. 14. Security Considerations 14.1 Gateway authentication method to SIP side of the IWF. 15. Known Issues 15.1 Resource reservation (RAI of H.323 )mapping in SIP. 15.2 Publishing of IWF dialing range automatically in SIP. At present, this needs to be configured statically in the SIP servers. 15.3 Support of Location request and mapping of the same in SIP Servers. Since H.323 terminals/gateway cannot receive LRQ messages (See Table 19/Section 7.7/H.225 [12]) to resolve addresses, the address resolution information cannot be properly distributed. 16. To Do 16.1 Call Flow diagrams does'nt reflect the calculations for finding the common subset of capabilities. This was not added because of simplicity and few additional call flow diagrams will be added in next release of the draft. 16.2 Message parameter mapping giving the details of every possible mapping will be added in next release of the draft. 16.3 Registration call flow diagrams will be added in the next release of the draft. 16.4 Call Release flow diagrams will be added in the next release of the draft. 16.5 Call flows showing SDP media description line ("m=") for each distinct session-ID of the OLC will be added in the next release of the draft. 16.6 Treatment of IWF and SIP network as a cluster and defining a zone from H.323 perspective. 16.7 Transfer of Qos (if any) to SIP network. Agarwal, et al. [Page 69] Internet Draft SIP-H.323 Interworking February 2001 16.8 The state machine will be further refined once the detail analysis of all call flows is completed. 17. Conclusion This draft is an attempt to define an agreed upon standard for the SIP and H.323 interworking. It will be updated based on the discussions on open mailing lists and implementors. Appendix A: Calculating common subset of capabilities The capability set of a terminal or a user agent refers to the set of algorithms for audio, video and data that it can support. It also conveys information about constraints in the selection of algorithms it may have. For example, due to limited bandwidth, a terminal may indicate that it can use either G.711 without video or G.723.1 with H.261 video. The operating mode of a call refers to the selected algorithms which are used for the actual transfer of media. To determine the operating mode for a call it is often necessary to find out the intersection of the capabilities of the endpoints in the conference. This section presents a way to calculate this intersection of the capability sets described by H.245 Terminal Capability Set (TCS) and that by SDP. A maximal intersection of two capability sets is a capability set which is a subset of both the capability sets and no other superset of the maximal intersection is a subset of those capability sets. It can be proven that if M is an operating mode for capability set C1 as well as for capability set C2, then M will be an operating mode for maximal intersection of C1 and C2. Thus, we fulfill requirement X described in Section X. H.245 defines Terminal Capabilities as a list of capability descriptors, ordered in decreasing preference. Any one of the capability descriptors can be used for selecting operating modes. Agarwal, et al. [Page 70] Internet Draft SIP-H.323 Interworking February 2001 Each capability descriptor includes a simultaneous capability set. Each element in the simultaneous capability set is an alternative capability set. Each element in the alternative capability set represents an algorithm. Each algorithm has a payload type and can be fully described by the payload type, a profile and some optional attributes. Convention: { } capability descriptor or simultaneous capability set [ ] alternative capability set Example: Let a1, a2, a3, a4, a5 be audio algorithms and v1, v2, v3 be video algorithms. C1 represents a capability set with two capability descriptors: C1 = { [a1, a2, a3] [v1, v2] } { [a1, a4, a5] [v1] } Operating modes could be (a1, v1), (a1, v2), (a4, v1), (a5), etc. Note that (a4, v2) is not an operating mode since a4 and v2 are drawn from different capability descriptors. Let C2 be another capability set. C2 = { [a1, a4, a2] [v1, v2, v3] } { [a1, a2, a5] [v1, v3] } Agarwal, et al. [Page 71] Internet Draft SIP-H.323 Interworking February 2001 The maximal intersection of C1 and C2 is C = { [a1, a2] [v1, v2] } { [a1, a4] [v1] } { [a1, a5] [v1] } Note that there are other capability sets which are intersections of C1 and C2 (e.g., {[a1,a2][v2]}), but they are subsets of C and hence can be derived from C. Algorithm for Finding Maximal Intersection of Capability Sets ---------------------------------------------------------------- An algorithm to find the maximal intersection of any two capability sets C1 and C2 is given below: 1. Set the result C to the empty set. 2. For each pair of capability descriptors (d1, d2), where d1 is from C1 and d2 is from C2, derive the permutations of alternative sets, s1 and s2. For each such permutation, where s1 is from d1 and s2 is from d2, intersect s1 and s2 (written as s=s1 ^ s2) and add s to C. 3. Remove duplicate entries from C. Example: Using the example with C1 and C2 given above, the outer loop runs for four iterations, since C1 and C2 both have two descriptors. Agarwal, et al. [Page 72] Internet Draft SIP-H.323 Interworking February 2001 1. d1 = {[a1,a2,a3][v1,v2]}, d2 = {[a1,a4,a2][v1,v2,v3]} Inner loop runs for 2 iterations: 1) {[a1,a2,a3]^[a1,a4,a2],[v1,v2]^[v1,v2,v3]} = {[a1,a2][v1,v2]} 2) {[a1,a2,a3]^[v1,v2,v3],[v1,v2]^[a1,a4,a2]} = {[][]} /* Empty set */ 2. d1 = {[a1,a4,a5][v1]}, d2 = {[a1,a4,a2][v1,v2,v3]} 1) {[a1,a4,a5]^[a1,a4,a2], [v1] ^[v1,v2,v3]} = {[a1,a4][v1]} 2) {[a1,a4,a5]^[v1,v2,v3],[v1]^[a1,a4,a2]} = {[][]} /* Empty set */ 3. d1 = {[a1,a2,a3][v1,v2]}, d2 = {[a1,a2,a5][v1,v3]} 1) {[a1,a2,a3]^[a1,a2,a5],[v1,v2]^[v1,v3]} = {[a1,a2][v1]} 2) {[a1,a2,a3]^[v1,v3],[v1,v2]^[a1,a2,a5]} = {[][]} /* Empty set */ 4. d1 = {[a1,a4,a5][v1]}, Agarwal, et al. [Page 73] Internet Draft SIP-H.323 Interworking February 2001 d2 = {[a1,a2,a5][v1,v3]} 1) {[a1,a4,a5]^[a1,a2,a5],[v1]^[v1,v3]} = {[a1,a5][v1]} 2) {[a1,a4,a5]^[v1,v3],[v1]^[a1,a2,a5]} = {[][]} /* Empty set */ After these iterations the intersection set becomes { [a1,a2] [v1,v2] } { } { [a1,a2] [v1] } { } { [a1,a4] [v1] } { } { [a1,a5] [v1] } { } After removing duplicates, the maximal intersection is { [a1,a2] [v1,v2] } { [a1,a4] [v1] } { [a1,a5] [v1] } Since H.323 does not require that all algorithms listed within a single alternative capability have the same media type, we need the inner loop to find out all the possible combinations. For example, if C1 = {[a1,a2,a3] [a1,a4,v2,v1]} and C2 = {[a1,a4,v2] [v1,v2,v3]}, then the above algorithm correctly finds the intersection as {[a1] [v1,v2]} {[a1,a4,v2]} Appendix B: Advertisement of SIP Support by H.323 Gateways Agarwal, et al. [Page 74] Internet Draft SIP-H.323 Interworking February 2001 ----------------------------------------------------------- SupportedProtocols ::= CHOICE { nonStandardData NonStandardParameter, h310 H310Caps, h320 H320Caps, h321 H321Caps, h322 H322Caps, h323 H323Caps, h324 H324Caps, voice VoiceCaps, t120-only T120OnlyCaps, ..., nonStandardProtocol NonStandardProtocol, t38FaxAnnexbOnly T38FaxAnnexbOnlyCaps, sip SIPCaps } SIPCaps ::= SEQUENCE { nonStandardData NonStandardParameter OPTIONAL, dataRatesSupported SEQUENCE OF DataRate OPTIONAL, supportedPrefixes SEQUENCE OF SupportedPrefix, ... } CallCapacityInfo ::= SEQUENCE { voiceGwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h310GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h320GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h321GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h322GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h323GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, h324GwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, t120OnlyGwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, t38FaxAnnexbOnlyGwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, terminalCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, mcuCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL, ..., Agarwal, et al. [Page 75] Internet Draft SIP-H.323 Interworking February 2001 sipGwCallsAvailable SEQUENCE OF CallsAvailable OPTIONAL } Appendix C: Message Details of Call Flows ------------------------------------------------------------- C.1 Simple Call from H.323 terminal to SIP terminal. Message Details. F1 Setup H.323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 sourceAddress : e164 address : 01000220013101720 h323-ID address : UserA19284 e164 address : 7199557429 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false Agarwal, et al. [Page 76] Internet Draft SIP-H.323 Interworking February 2001 destinationAddress : h323-ID Address : UserB@there.com destCallSignalAddress : ipAddress : ip : 164.164.28.121 port : 1720 activeMC : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.101 port : 3472 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) mediaWaitForConnect : false canOverlapSend : false h245Tunneling : false } Setup specifies the called endpoint address in H323 Id of destination address. This H323Id will be resolved at the IWF and the destination call signalling address in this case will be the call signalling address of IWF. IWF uses the destination alias address for resolving the destination endpoint and routes the call to endpoint B. F2 INVITE IWF -> SIP INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Agarwal, et al. [Page 77] Internet Draft SIP-H.323 Interworking February 2001 Content-Type: application/sdp Content-Length: ... v=0 o=IWF 2890844526 2890844526 IN IP4 164.164.28.121 s=- c=IN IP4 164.164.28.121 t=3034423619 0 m=audio 5004 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F3 CallProc IWF -> H.323 H323-UserInformation { h323-uu-pdu : h323-message-body : callproceeding : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : gateway callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) } Call Proceeding will tell the calling endpoint that the call is routed through a gateway. F4 (100 Trying) SIP -> IWF SIP/2.0 100 Trying Via: SIP/2.0/UDP 164.164.28.121:5060 From: Agarwal, et al. [Page 78] Internet Draft SIP-H.323 Interworking February 2001 To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Content-Length: 0 F5 180 Ringing SIP -> IWF SIP/2.0 100 Trying Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Content-Length: 0 F6 Alerting IWF -> H.323 H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : gateway callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) } F7 200 OK IWF -> SIP Agarwal, et al. [Page 79] Internet Draft SIP-H.323 Interworking February 2001 SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F8 Connect IWF -> H.323 H323-UserInformation { h323-uu-pdu : h323-message-body : callproceeding : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.141 port : 2000 destinationInfo : gateway conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) Agarwal, et al. [Page 80] Internet Draft SIP-H.323 Interworking February 2001 callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) } H245 Address specified in Connect message will give the information about the H.245 channel of endpoint B. This will be used to establish the H.245 control channel. F9 ACK IWF -> SIP ACK sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 ACK Content-Length: 0 F10 TCS H.323 -> IWF H245 MultimediaSystemControlMessage { request : terminalCapabilitySet : sequenceNumber : 1 protocolIdentifer : itu-t : recommendation : h : 245 : version : 3 multiplexCapability : h2250Capability : maximumAudioDelayJitter : 60 receiveMultipointCapability : multicastCapability : false multiUniCastConference : false Agarwal, et al. [Page 81] Internet Draft SIP-H.323 Interworking February 2001 mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false mcCapability : centralizedConferenceMC : false deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 capability : receiveAudioCapability : g711Ulaw-64k : 60 capabilityTableEntryNumber : 7110 capability : Agarwal, et al. [Page 82] Internet Draft SIP-H.323 Interworking February 2001 receiveAudioCapability : g711Alaw64k : 60 capabilityTableEntryNumber : 728 capability : receiveAudioCapability : g728 : 60 capabilityTableEntryNumber : 261 capability : receiveVideoCapability : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false capabilityTableEntryNumber : 263 capability : receiveVideoCapability : h263VideoCapability : sqcifMPI : 1 [1/29.97 Hz] qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] maxBitRate : 1000 [100 bit/s] unrestrictedVector : false arithmeticCoding : false advancedPrediction : false pbFrames : false temporalSpatialTradeOffCapability : false errorCompensation : false capabilityTableEntryNumber : 7231 capability : receiveAudioCapability : g7231 : maxA1-sduAudioFrames : 8 silenceSuppression : false capabilityTableEntryNumber : 120 capability : receiveAndTransmitDataApplicationCapability : Agarwal, et al. [Page 83] Internet Draft SIP-H.323 Interworking February 2001 application : t120 : separateLANStack : maxBitRate : 1000 [100 bit/s] capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 7110 7231 728 : 261 263 : 120 } F11 TCSAck IWF -> H.323 H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } F12 TCS IWF -> H.323 H245 MultimediaSystemControlMessage { request : terminalCapabilitySet : sequenceNumber : 1 protocolIdentifer : itu-t : recommendation : h : 245 : version : 3 multiplexCapability : Agarwal, et al. [Page 84] Internet Draft SIP-H.323 Interworking February 2001 h2250Capability : maximumAudioDelayJitter : 60 receiveMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false mcCapability : centralizedConferenceMC : false deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 Agarwal, et al. [Page 85] Internet Draft SIP-H.323 Interworking February 2001 capability : receiveAudioCapability : g711Ulaw-64k : 60 capabilityTableEntryNumber : 7110 capability : receiveAudioCapability : g711Alaw64k : 60 capabilityTableEntryNumber : 728 capability : receiveAudioCapability : g728 : 60 capabilityTableEntryNumber : 261 capability : receiveVideoCapability : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false capabilityTableEntryNumber : 263 capability : receiveVideoCapability : h263VideoCapability : sqcifMPI : 1 [1/29.97 Hz] qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] maxBitRate : 1000 [100 bit/s] unrestrictedVector : false arithmeticCoding : false advancedPrediction : false pbFrames : false temporalSpatialTradeOffCapability : false errorCompensation : false capabilityTableEntryNumber : 7231 capability : receiveAudioCapability : g7231 : Agarwal, et al. [Page 86] Internet Draft SIP-H.323 Interworking February 2001 maxA1-sduAudioFrames : 8 silenceSuppression : false capabilityTableEntryNumber : 120 capability : receiveAndTransmitDataApplicationCapability : application : t120 : separateLANStack : maxBitRate : 1000 [100 bit/s] capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 7110 7231 728 : 261 263 : 120 } F13 TCSAck H.323 -> IWF H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } F14 MSD H.323 -> IWF H245 MultimediaSystemControlMessage { request : masterSlaveDetermination : terminalType : 50 statusDeterminationNumber : 8524727 } Agarwal, et al. [Page 87] Internet Draft SIP-H.323 Interworking February 2001 F14A MSD IWF -> H.323 H245 MultimediaSystemControlMessage { request : masterSlaveDetermination : terminalType : 60 statusDeterminationNumber : 5996695 } F15 MSDAck IWF -> H.323 MasterSlaveDeterminationAck H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : master } F16 MSDAck H323 -> IWF H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : slave } F17 OLC H.323 -> IWF OpenLogicalChannel (RTCP=2327,g711Ulaw) H245 MultimediaSystemControlMessage { request : Agarwal, et al. [Page 88] Internet Draft SIP-H.323 Interworking February 2001 openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 transportCapability : QOSCapabilities : rsvpParameters : qosMode : guaranteedQOS tokenRate : 23 [bytes/sec] bucketSize : -1 [bytes] peakRate : -1 [bytes/sec] minPoliced : -1 maxPktSize : -1 [bytes] atmParameters : maxNTUSize : 10 [octets] atmUBR : false atmrtVBR : false atmnrtVBR : false atmABR : false atmCBR : true } F18 OLCAck IWF -> H.323 OpenLogicalChannelAck (RTP=4326, 164.164.28.141) H245 MultimediaSystemControlMessage { response : Agarwal, et al. [Page 89] Internet Draft SIP-H.323 Interworking February 2001 openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 flowControlToZero : true } F19 OLC IWF -> H.323 OpenLogicalChannel (RTCP=4347,g711Ulaw) H245 MultimediaSystemControlMessage { request : openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 } Agarwal, et al. [Page 90] Internet Draft SIP-H.323 Interworking February 2001 F20 OLCAck H.323 -> IWF OpenLogicalChannelAck (RTP=2326, 164.164.28.101) H245 MultimediaSystemControlMessage { response : openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 flowControlToZero : true } F21 INVITE IWF -> SIP INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 Agarwal, et al. [Page 91] Internet Draft SIP-H.323 Interworking February 2001 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F22 200 OK SIP -> IWF SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F23 ACK IWF -> SIP ACK sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 ACK Content-Length: 0 ------------------------------------------------------------------ Agarwal, et al. [Page 92] Internet Draft SIP-H.323 Interworking February 2001 C.2 Call from H.323 terminal to SIP terminal using H.245 tunneling Message Details. F1 Setup H.323 -> IWF Setup UserB@there.com H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.101 port : 2000 sourceAddress : e164 address : 01000220013101720 h323-ID address : UserA@here.com e164 address : 7199557429 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false destinationAddress : Agarwal, et al. [Page 93] Internet Draft SIP-H.323 Interworking February 2001 h323-ID address : UserB@there.com destCallSignalAddress : ipAddress : ip : 164.164.28.121 port : 1720 activeMC : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.101 port : 3472 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) mediaWaitForConnect : false canOverlapSend : false h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage : request : terminalCapabilitySet : sequenceNumber : 1 protocolIdentifer : itu-t : recommendation : h : 245 : version : 3 multiplexCapability : h2250Capability : maximumAudioDelayJitter : 60 receiveMultipointCapability : multicastCapability : false Agarwal, et al. [Page 94] Internet Draft SIP-H.323 Interworking February 2001 multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false mcCapability : centralizedConferenceMC : false deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 capability : receiveAudioCapability : g711Ulaw-64k : 60 capabilityTableEntryNumber : 7110 Agarwal, et al. [Page 95] Internet Draft SIP-H.323 Interworking February 2001 capability : receiveAudioCapability : g711Alaw64k : 60 capabilityTableEntryNumber : 728 capability : receiveAudioCapability : g728 : 60 capabilityTableEntryNumber : 261 capability : receiveVideoCapability : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false capabilityTableEntryNumber : 263 capability : receiveVideoCapability : h263VideoCapability : sqcifMPI : 1 [1/29.97 Hz] qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] maxBitRate : 1000 [100 bit/s] unrestrictedVector : false arithmeticCoding : false advancedPrediction : false pbFrames : false temporalSpatialTradeOffCapability : false errorCompensation : false capabilityTableEntryNumber : 7231 capability : receiveAudioCapability : Agarwal, et al. [Page 96] Internet Draft SIP-H.323 Interworking February 2001 g7231 : maxA1-sduAudioFrames : 8 silenceSuppression : false capabilityTableEntryNumber : 120 capability : receiveAndTransmitDataApplicationCapability : application : t120 : separateLANStack : maxBitRate : 1000 [100 bit/s] capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 7110 7231 728 : 261 263 : 120 : h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage : request : masterSlaveDetermination : terminalType : 50 statusDeterminationNumber : 10712223 } F2 INVITE IWF -> SIP INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Agarwal, et al. [Page 97] Internet Draft SIP-H.323 Interworking February 2001 Content-Length: 0 F3 180 Ringing SIP -> IWF SIP/2.0 100 Trying Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Content-Length: 0 F4 Alerting IWF -> H.323 H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : gateway callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) } F5 200 OK SIP -> IWF SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 From: Agarwal, et al. [Page 98] Internet Draft SIP-H.323 Interworking February 2001 To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F6 Connect IWF -> H.323 Connect (MSD Ack, TCS Ack, TCS) H323-UserInformation { h323-uu-pdu : h323-message-body : connect : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.141 port : 2002 destinationInfo : vendor : vendor : t32CountryCode : 11 Agarwal, et al. [Page 99] Internet Draft SIP-H.323 Interworking February 2001 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 gateway : mc : false undefinedNode : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : master } : h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } h245Control - Sequence[ 2 ] H245 MultimediaSystemControlMessage : request : terminalCapabilitySet : Agarwal, et al. [Page 100] Internet Draft SIP-H.323 Interworking February 2001 sequenceNumber : 1 protocolIdentifer : itu-t : recommendation : h : 245 : version : 3 multiplexCapability : h2250Capability : maximumAudioDelayJitter : 60 receiveMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false Agarwal, et al. [Page 101] Internet Draft SIP-H.323 Interworking February 2001 mcCapability : centralizedConferenceMC : false deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 capability : receiveAudioCapability : g711Ulaw-64k : 60 capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 } F7 Facility H.323 -> IWF Facility (TCS Ack, MSD Ack, OLC) H323-UserInformation { h323-uu-pdu : h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : Agarwal, et al. [Page 102] Internet Draft SIP-H.323 Interworking February 2001 H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : slave h245Control - Sequence[ 2 ] : H245 MultimediaSystemControlMessage { request : openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 } } F8 Facility IWF -> H323 Agarwal, et al. [Page 103] Internet Draft SIP-H.323 Interworking February 2001 Facility (OLC Ack, OLC) H323-UserInformation { h323-uu-pdu : h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 Agarwal, et al. [Page 104] Internet Draft SIP-H.323 Interworking February 2001 tsapIdentifier : 4327 flowControlToZero : true } h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { request : openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 } } F9 Facility H323 -> IWF Facility (OLC Ack) H323-UserInformation { h323-uu-pdu : h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version Agarwal, et al. [Page 105] Internet Draft SIP-H.323 Interworking February 2001 : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.121 tsapIdentifier : 2326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.121 tsapIdentifier : 2327 flowControlToZero : true } } F10 ACK IWF -> SIP ACK sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Agarwal, et al. [Page 106] Internet Draft SIP-H.323 Interworking February 2001 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 ACK Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 --------------------------------------------------------------- C.3 Call from H.323 terminal to SIP terminal using fast connect procedure. Message Details --------------- F1 Setup (fastStart=true,OLC) H323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.101 Agarwal, et al. [Page 107] Internet Draft SIP-H.323 Interworking February 2001 port : 2000 sourceAddress : e164 address : 01000220013101720 h323-ID address : UserB@there.com e164 address : 7199557429 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false destCallSignalAddress : ipAddress : ip : 164.164.28.121 port : 1720 activeMC : false conferenceID : Hex( 56 34 34 34 34 EF 0B 00 21 21 E4 A5 35 A3 9A 82) conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.101 port : 1700 callIdentifier : guid : Hex( 56 34 34 34 34 EF 0A 00 21 21 E4 A5 35 A3 9A 82 ) fastStart : fastStart - Sequence[ 0 ] : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : Agarwal, et al. [Page 108] Internet Draft SIP-H.323 Interworking February 2001 audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 : fastStart - Sequence[ 1 ] : forwardLogicalChannelNumber : 2 forwardLogicalChannelParameters : dataType : audioData : g7231 : maxA1-sduAudioFrames : 8 silenceSuppression : false multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 : fastStart - Sequence[ 2 ] : forwardLogicalChannelNumber : 4762 forwardLogicalChannelParameters : dataType : nullData : multiplexParameters : none : reverseLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : Agarwal, et al. [Page 109] Internet Draft SIP-H.323 Interworking February 2001 h2250LogicalChannelParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 : fastStart - Sequence[ 3 ] : forwardLogicalChannelNumber : 4762 forwardLogicalChannelParameters : dataType : nullData : multiplexParameters : none : reverseLogicalChannelParameters : dataType : audioData : g7231 : maxA1-sduAudioFrames : 8 silenceSuppression : false multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 : Agarwal, et al. [Page 110] Internet Draft SIP-H.323 Interworking February 2001 fastStart - Sequence[ 4 ] : forwardLogicalChannelNumber : 3 forwardLogicalChannelParameters : dataType : videoData : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false multiplexParameters : h2250LogicalChannelParameters : sessionID : 2 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2329 : fastStart - Sequence[ 5 ] : forwardLogicalChannelNumber : 4762 forwardLogicalChannelParameters : dataType : nullData : multiplexParameters : none : reverseLogicalChannelParameters : dataType : videoData : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false multiplexParameters : h2250LogicalChannelParameters : Agarwal, et al. [Page 111] Internet Draft SIP-H.323 Interworking February 2001 sessionID : 2 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2328 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2329 : mediaWaitForConnect : false canOverlapSend : false h245Tunneling : false } F2 INVITE IWF -> SIP INVITE sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 Agarwal, et al. [Page 112] Internet Draft SIP-H.323 Interworking February 2001 F3 180 RINGING SIP -> IWF SIP/2.0 100 Trying Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Content-Length: 0 F4 Alerting IWF -> H323 H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : gateway callIdentifier : Hex( 56 34 34 34 34 EF 0A 00 21 21 E4 A5 35 A3 9A 82 ) } F5 200 OK SIP -> IWF SIP/2.0 200 OK Agarwal, et al. [Page 113] Internet Draft SIP-H.323 Interworking February 2001 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F6 Connect (fastStart=true,OLC) IWF -> H323 H323-UserInformation { h323-uu-pdu : h323-message-body : connect : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 gateway : Agarwal, et al. [Page 114] Internet Draft SIP-H.323 Interworking February 2001 mc : false undefinedNode : false conferenceID : Hex( 56 34 34 34 34 EF 0B 00 21 21 E4 A5 35 A3 9A 82 ) callIdentifier : guid : Hex( 56 34 34 34 34 EF 0A 00 21 21 E4 A5 35 A3 9A 82 ) fastStart : fastStart - Sequence[ 0 ] : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 : fastStart - Sequence[ 1 ] : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : nullData : multiplexParameters : none : reverseLogicalChannelParameters : dataType : audioData : Agarwal, et al. [Page 115] Internet Draft SIP-H.323 Interworking February 2001 g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 : : h245Tunneling : false } F7 Ack IWF -> SIP ACK sip:UserB@there.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=9876 Call-ID: 4423493498581@164.164.28.121 CSeq: 1024 ACK Content-Length: 0 --------------------------------------------------------- C.4 Call from H.323 terminal to SIP terminal using overlapped sending. Message Details. F1 Setup H.323 -> IWF Agarwal, et al. [Page 116] Internet Draft SIP-H.323 Interworking February 2001 Setup(CanOverlapSend=True, CgPn=555-1212, CdPn=214-555-1313) H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 sourceAddress : e164 address : 01000220013101720 h323-ID address : UserA19284 e164 address : 7199557429 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false destinationAddress : e164 address : 555-1212 destCallSignalAddress : ipAddress : ip : 164.164.28.121 port : 1720 activeMC : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) Agarwal, et al. [Page 117] Internet Draft SIP-H.323 Interworking February 2001 conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.101 port : 3472 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) mediaWaitForConnect : false canOverlapSend : true h245Tunneling : false } F2 Setup Ack IWF -> H.323 Setup Ack { Protocol Identifier : itu-t : recommendation : h : 2250 : version : 2 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) Message type : 11011 (Bits) Progress indicator : 0001000 (Octet 4) } F3 INVITE IWF -> SIP Agarwal, et al. [Page 118] Internet Draft SIP-H.323 Interworking February 2001 INVITE sip:555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1 INVITE Contact: Content-Length: 0 F4 484 Address Incomplete SIP -> IWF SIP/2.0 484 Address Incomplete Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=34239188 Call-ID: 4423493498581@164.164.28.121 CSeq: 1 INVITE Content-Length: 0 F5 ACK IWF -> SIP ACK sip:555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=34239188 Call-ID: 4423493498581@164.164.28.121 CSeq: 1 ACK Content-Length: 0 F6 Information H.323 -> IWF Information (CdPn=972-555-1212) H323-UserInformation { h323-uu-pdu : h323-message-body : Agarwal, et al. [Page 119] Internet Draft SIP-H.323 Interworking February 2001 information : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) } F7 INVITE IWF -> SIP INVITE sip:+1-972-555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1 INVITE Contact: Content-Length: 0 F8 180 Ringing SIP -> IWF SIP/2.0 180 Ringing Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=843423 Call-ID: 4423493498581@164.164.28.121 CSeq: 1 INVITE Content-Length: 0 F9 Alerting IWF -> H.323 Agarwal, et al. [Page 120] Internet Draft SIP-H.323 Interworking February 2001 H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : gateway callIdentifier : Hex( 56 34 34 34 34 EF 0A 00 21 21 E4 A5 35 A3 9A 82 ) } F10 200 OK SIP -> IWF SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: ;tag=843423 Call-ID: 4423493498581@164.164.28.121 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 Agarwal, et al. [Page 121] Internet Draft SIP-H.323 Interworking February 2001 F11 Connect IWF -> H.323 Connect H323-UserInformation { h323-uu-pdu : h323-message-body : callproceeding : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.141 port : 2000 destinationInfo : gateway conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) } F12 H245 H.323 <-> IWF H245 F13 ACK IWF -> SIP ACK sip:+1-972-555-1212@164.164.28.121 SIP/2.0 Agarwal, et al. [Page 122] Internet Draft SIP-H.323 Interworking February 2001 Via: SIP/2.0/UDP 164.164.28.121:5060 From: To: Call-ID: 4423493498581@164.164.28.121 CSeq: 1 ACK Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 --------------------------------------------------------------------- C.4 Simple call from SIP terminal to H.323 terminal. Message Details F1 INVITE SIP -> IWF INVITE sip:UserA@here.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 Agarwal, et al. [Page 123] Internet Draft SIP-H.323 Interworking February 2001 F2 Setup IWF -> H.323 Setup H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 sourceInfo : gateway sourceAddress : e164 address : 01000220013101720 h323-ID address : UserB@there.com e164 address : 7199557429 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false destinationAddress : h323-ID Address : UserA@here.com destCallSignalAddress : ipAddress : ip : 164.164.28.141 port : 1720 activeMC : false Agarwal, et al. [Page 124] Internet Draft SIP-H.323 Interworking February 2001 conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.101 port : 3472 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) mediaWaitForConnect : false canOverlapSend : false h245Tunneling : false } F3 Alerting H.323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 destinationInfo : terminal callIdentifier : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) } F4 180 Ringing IWF -> SIP Agarwal, et al. [Page 125] Internet Draft SIP-H.323 Interworking February 2001 SIP/2.0 180 Ringing Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Content-Length: 0 F5 Connect H.323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : callproceeding : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.141 port : 2000 destinationInfo : terminal conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB) callIdentifier : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB) } F6 H.245 IWF <-> H.323 H.245 Agarwal, et al. [Page 126] Internet Draft SIP-H.323 Interworking February 2001 F7 200 OK IWF -> SIP SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F8 ACK SIP -> IWF ACK sip:UserA876665@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 ACK Content-Length: 0 ----------------------------------------------------------- C.5 Call from SIP terminal to H.323 terminal using H.245 tunneling. Message Details F1 INVITE SIP -> IWF Agarwal, et al. [Page 127] Internet Draft SIP-H.323 Interworking February 2001 INVITE sip:UserA@here.com SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 Setup(tunn.=true,TCS,MSD) IWF -> H323 H323-UserInformation { h323-uu-pdu : h323-message-body : setup : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.101 port : 2000 sourceAddress : e164 address : 01000220013101720 h323-ID address : UserB@there.com e164 address : 7199557429 Agarwal, et al. [Page 128] Internet Draft SIP-H.323 Interworking February 2001 sourceInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 terminal : mc : false undefinedNode : false destCallSignalAddress : ipAddress : ip : 164.164.28.141 port : 1720 activeMC : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) conferenceGoal : create callType : pointToPoint sourceCallSignalAddress : ipAddress : ip : 164.164.28.121 port : 3472 callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) mediaWaitForConnect : false canOverlapSend : false h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage : request : terminalCapabilitySet : sequenceNumber : 1 protocolIdentifer : itu-t Agarwal, et al. [Page 129] Internet Draft SIP-H.323 Interworking February 2001 : recommendation : h : 245 : version : 3 multiplexCapability : h2250Capability : maximumAudioDelayJitter : 60 receiveMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false mcCapability : centralizedConferenceMC : false Agarwal, et al. [Page 130] Internet Draft SIP-H.323 Interworking February 2001 deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 capability : receiveAudioCapability : g711Ulaw-64k : 60 capabilityTableEntryNumber : 7110 capability : receiveAudioCapability : g711Alaw64k : 60 capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 : h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage : request : masterSlaveDetermination : terminalType : 60 statusDeterminationNumber : 10712223 } F3 Alerting(tunn.=true,TCSAck,MSD Ack, TCS) H323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : alerting : protocolIdentifier : itu-t : recommendation : h : 2250 : version Agarwal, et al. [Page 131] Internet Draft SIP-H.323 Interworking February 2001 : 2 destinationInfo : terminal callIdentifier : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : slave } : h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } h245Control - Sequence[ 2 ] H245 MultimediaSystemControlMessage : request : terminalCapabilitySet : sequenceNumber : 1 protocolIdentifer : itu-t : recommendation : h : 245 : version : 3 multiplexCapability : h2250Capability : maximumAudioDelayJitter : 60 Agarwal, et al. [Page 132] Internet Draft SIP-H.323 Interworking February 2001 receiveMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false transmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false receiveAndTransmitMultipointCapability : multicastCapability : false multiUniCastConference : false mediaDistributionCapability : centralizedControl : false distributedControl : false centralizedAudio : false distributedAudio : false centralizedVideo : false distributedVideo : false mcCapability : centralizedConferenceMC : false deCentralizedConferenceMC : false rtcpVideoControlCapability : false mediaPacketizationCapability : h261aVideoPacketization : false capabilityTable : capabilityTableEntryNumber : 7111 capability : receiveAudioCapability : Agarwal, et al. [Page 133] Internet Draft SIP-H.323 Interworking February 2001 g711Ulaw-64k : 60 capabilityTableEntryNumber : 7110 capability : receiveAudioCapability : g711Alaw64k : 60 capabilityTableEntryNumber : 728 capability : receiveAudioCapability : g728 : 60 capabilityTableEntryNumber : 261 capability : receiveVideoCapability : h261VideoCapability : qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] temporalSpatialTradeOffCapability : false maxBitRate : 600 [100 bit/sec] stillImageTransmission : false capabilityTableEntryNumber : 263 capability : receiveVideoCapability : h263VideoCapability : sqcifMPI : 1 [1/29.97 Hz] qcifMPI : 1 [1/29.97 Hz] cifMPI : 1 [1/29.97 Hz] maxBitRate : 1000 [100 bit/s] unrestrictedVector : false arithmeticCoding : false advancedPrediction : false pbFrames : false temporalSpatialTradeOffCapability : false errorCompensation : false Agarwal, et al. [Page 134] Internet Draft SIP-H.323 Interworking February 2001 capabilityTableEntryNumber : 7231 capability : receiveAudioCapability : g7231 : maxA1-sduAudioFrames : 8 silenceSuppression : false capabilityTableEntryNumber : 120 capability : receiveAndTransmitDataApplicationCapability : application : t120 : separateLANStack : maxBitRate : 1000 [100 bit/s] capabilityDescriptors : capabilityDescriptorNumber : 0 simultaneousCapabilities : 7111 7110 7231 728 : 261 263 : 120 } F4 180 Ringing IWF -> SIP SIP/2.0 180 Ringing Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Content-Length: 0 F5 Facility(TCS Ack,OLC,MSD Ack) IWF -> H323 H323-UserInformation { h323-uu-pdu : Agarwal, et al. [Page 135] Internet Draft SIP-H.323 Interworking February 2001 h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : terminalCapabilitySetAck : sequenceNumber : 1 } h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { response : masterSlaveDeterminationAck : decision : master } h245Control - Sequence[ 2 ] : H245 MultimediaSystemControlMessage { request : openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : Agarwal, et al. [Page 136] Internet Draft SIP-H.323 Interworking February 2001 dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 } } F6 Facility (OLC Ack,OLC) H323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage Agarwal, et al. [Page 137] Internet Draft SIP-H.323 Interworking February 2001 { response : openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 flowControlToZero : true } h245Control - Sequence[ 1 ] : H245 MultimediaSystemControlMessage { request : openLogicalChannel : forwardLogicalChannelNumber : 1 forwardLogicalChannelParameters : dataType : audioData : g711Ulaw-64k : 60 multiplexParameters : h2250LogicalChannelParameters : sessionID : 1 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.141 tsapIdentifier : 4327 } Agarwal, et al. [Page 138] Internet Draft SIP-H.323 Interworking February 2001 } F7 Facility (OLC Ack) IWF -> OLC H323-UserInformation { h323-uu-pdu : h323-message-body : facility : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 reason : callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true h245Control : h245Control - Sequence[ 0 ] : H245 MultimediaSystemControlMessage { response : openLogicalChannelAck : forwardLogicalChannelNumber : 1 forwardMultiplexAckParameters : h2250LogicalChannelAckParameters : sessionID : 1 mediaChannel : unicastAddress : iPAddress : Agarwal, et al. [Page 139] Internet Draft SIP-H.323 Interworking February 2001 network : 164.164.28.101 tsapIdentifier : 2326 mediaControlChannel : unicastAddress : iPAddress : network : 164.164.28.101 tsapIdentifier : 2327 flowControlToZero : true } } F8 Connect H323 -> IWF H323-UserInformation { h323-uu-pdu : h323-message-body : connect : protocolIdentifier : itu-t : recommendation : h : 2250 : version : 2 h245Address : ipAddress : ip : 164.164.28.141 port : 2002 destinationInfo : vendor : vendor : t32CountryCode : 11 t32Extension : 11 manufacturerCode : 11 productId : IWF versionId : SIP-H323 gateway : mc : false Agarwal, et al. [Page 140] Internet Draft SIP-H.323 Interworking February 2001 undefinedNode : false conferenceID : Hex( 56 34 34 34 34 EF 09 00 21 21 E4 83 2D 7E BA AB ) callIdentifier : guid : Hex( 56 34 34 34 34 EF 08 00 21 21 E4 83 2D 7E BA AB ) h245Tunneling : true } F9 200 OK IWF -> SIP SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F10 ACK SIP -> IWF ACK sip:UserA876665@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: ;tag=a563s1 Call-ID: 56-23-12-12@164.164.28.141 Agarwal, et al. [Page 141] Internet Draft SIP-H.323 Interworking February 2001 CSeq: 1 ACK Content-Length: 0 -------------------------------------------------------------- C.6 Call from SIP terminal to H.323 terminal using overlapped sending. Message Details F1 INVITE SIP -> IWF INVITE sip:555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 Setup IWF -> H.323 H.225 Setup(canOverlapSend=true, incomplete address) F3 484 Address Incomplete SIP -> IWF SIP/2.0 484 Address Incomplete Agarwal, et al. [Page 142] Internet Draft SIP-H.323 Interworking February 2001 Via: SIP/2.0/UDP 164.164.28.121:5060 To: ;tag=132328u439834234 From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Content-Length: 0 F4 ACK SIP -> IWF ACK sip:555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: ;tag=132328u439834234 From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 ACK Content-Length: 0 F5 Setup Ack H.323 -> IWF H.225 Setup Ack F6 INVITE SIP -> IWF INVITE sip:+1-972-555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserB 2890844526 2890844526 IN IP4 164.164.28.141 s=- c=IN IP4 164.164.28.141 Agarwal, et al. [Page 143] Internet Draft SIP-H.323 Interworking February 2001 t=3034423619 0 m=audio 4346 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F7 Information IWF -> H.323 H.225 Information (Additional Address) F8 Alerting H.323 -> IWF H.225 Alerting F9 180 Ringing SIP -> IWF SIP/2.0 180 Ringing Via: SIP/2.0/UDP 164.164.28.121:5060 To: ;tag=81902834 From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Content-Length: 0 F10 Connect H.323 -> IWF H.225 Connect F11 H245 H.323 <-> IWF H.245 message exchange F12 200 OK IWF -> SIP SIP/2.0 200 OK Via: SIP/2.0/UDP 164.164.28.121:5060 Agarwal, et al. [Page 144] Internet Draft SIP-H.323 Interworking February 2001 To: ;tag=81902834 From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: ... v=0 o=UserA 2890844526 2890844526 IN IP4 164.164.28.101 s=- c=IN IP4 164.164.28.101 t=3034423619 0 m=audio 2326 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F13 ACK SIP -> IWF ACK sip:+1-972-555-1212@164.164.28.121 SIP/2.0 Via: SIP/2.0/UDP 164.164.28.121:5060 To: ;tag=81902834 From: Call-ID: 56-23-12-12@164.164.28.141 CSeq: 1 ACK Content-Length: 0 Appendix D : Summary of SIP-H.323 Interworking Requirements This is the summary of the requirements mentioned in SIP-H.323 interworking draft [9] for basic call handling. The Sip-H.323 requirements draft [9] provides the detail requirements for SIP-H.323 Interworking based on H.323 Version 2 [5] and SIP RFC- 2543 [3]. There are two phases of the interworking standard. The first phase will define the basic call establishment and termination. The second phase will include some optional, advanced features, and Agarwal, et al. [Page 145] Internet Draft SIP-H.323 Interworking February 2001 services. Both phases have to meet the general requirements specified in the following sections. A high-level summary of the requirements is described as stated below: D.1. Functionality within the Interowkrking Function (IWF): The IWF may have the look-up tables for SIP and H.323 address resolution. It may contain the functions like Call sequence mapping, Address resolution, Terminal Capability transactions, Opening and closing of media channels, Mapping media algorithms for H.323 and SIP network, Call resource reservation and release, Ability to provide the state of a call, Call state machine, Mid Call signal processing, and Service Interoperability Logic. No media processing will be done within the IWF. D.2. Pre-Call Requirements: The IWF shall support the address resolution schemes of both H.323 and SIP protocol and may register itself to the H.323 gatekeeper (GK) and the SIP server (Register, Redirect, Proxy). D.3. General Interworking Requirements D.3.1 Basic call Requirements D.3.1.1 General Requirements: The default call parameters shall be provided for the transaction along with resource release capability with detection of the call deactivation. D.3.1.2 Address Resolution: Both SIP and H.323 address resolution services shall be provided for both SIP and H.323 calls. D.3.1.3 Call with H.323 GKs: The addresses shall be resolved with the help of the GK where the GK is present and will act as a SIP user agent for registering with the H.323 GK. D.3.1.4 Call with SIP Servers: The addresses shall be resolved with the help of the SIP server where the SIP server is present and will act as an H.323 terminal for registering with the SIP server. D.3.1.5 Call with both H.323 GK and SIP Server: The IWF shall act both SIP user agent and H.323 terminal. Agarwal, et al. [Page 146] Internet Draft SIP-H.323 Interworking February 2001 D.3.1.6 Capability negotiation: It shall send all the capability descriptors of H.323 and SDP descriptors of SIP in the best possible way to each other without making any assumptions about the capabilities of either SIP user agent or H.323 terminal. However, it may indicate a default capability of H.323 terminal or SIP user agent even before exchanging capability with H.323 (using H.245) and SIP (using SDP). This default capability follows the mandatory capability requirements as defined by the respective protocols. D.3.1.7 Opening of logical channels: The IWF shall support unidirectional, symmetric bi-directional, and asymmetric bi-directional opening of channels, and will respond to the mode request and/or to the request for reopening and changing an existing logical channel. The support the flow control of H.323 shall also be provided. D.3.1.8 Handling of Media transmission and reception: The IWF shall not handle any RTP data. D.3.2 Requirements for support of fast connect procedures: The IWF shall shall support the fast Start element in H.323. D.3.3 Requirements for support of H.245 tunnelling: The IWF shall support the H.245 tunneling in the Setup message. D.3.4 Requirements for support of pre granted ARQ: The IWF shall support the pre-granted ARQ. In this case, it may do the address resolution from H.323 GK using LRQ/LCF exchange. D.3.5 Requirements for support of overlapped sending: The IWF shall support the overlapped sending of dialed digits by using the INFO method in SIP and Q.931 Setup, Setup Ack and Information Message in H.323. The IWF shall support the transfer of digits during a call by using INFO method in SIP and UserInputIndication in H.245(H.323). D.4. Transport: Both TCP and UDP shall be supported and the network does not assure QoS. The signaling messages have not priority over other messages. The Support for H.323Annex E (H.323 signaling over UDP) is optional. RTP shall be used for carrying media over both SIP and H.323 network. Agarwal, et al. [Page 147] Internet Draft SIP-H.323 Interworking February 2001 D.5. Mapping between SIP and H.323 D.5.1 General Procedures: Call message sequence shall be maintained in both directions. The messages that do not have a match on the other side should be terminated on the IWF, and IWF should take the necessary action on them. Information elements that are not in use on the H.323 side shall be generated by the IWF as required by the SIP protocol and vice versa. The SIP data fields shall be converted into the corresponding ASN.1 user-user information element structure. The user- user information element structure shall be generated according to specifications in Recommendation H.225.0 version 2.0 and H.245 version 4.0. D.5.2 H.323 Call Signalling (H.225.0) and SIP Call Signalling D.5.2.1. The IWF shall conform to the call signalling procedures recommended for the SIP side independent of the H.323 side. D.5.2.2. The IWF shall conform to the call signalling procedures recommended for the H.323 side independent of the SIP side. D.5.2.3. The IWF shall terminate the Q.931 Call Signalling Channel between an H.323 endpoint or H.323 Gatekeeper (in case of GK routed signalling) and the IWF on one hand and the call signalling (if any) between the IWF and the SIP endpoint on the other side. D.5.2.4. The IWF shall terminate the RAS Channel between H.323 Gatekeeper (if any) and IWF. D.5.2.5. Messages for supplementary services (FACILITY, NOTIFY, and the INFORMATION messages) in H.323 side may be processed by the IWF only if the service is supported. D.5.3 H.323 Call Control (H.245) and SIP Call Control (SDP): IWF should try to map the H.245 and SDP to the maximum extent. D.5.4 H.323 audio/video codec to SIP media formats: The IWF should provide invisible support for all audio, video, and/or data algorithms commonly supported by both ITU and IANA. Agarwal, et al. [Page 148] Internet Draft SIP-H.323 Interworking February 2001 D.5.5 Call sequence: The call sequence on both sides should be maintained in such a way that neither H.323 terminal nor SIP UA is aware of the IWF presence. The IWF should provide seamless interworking between the call flows of the two protocols. The IWF will not make any modifications to the normal call flows of either protocols .The messages and parameters which do not have direct mapping on the other side are to be generated by the IWF with default parameters in most cases. D.6. State Machine Requirements: Unexpected messages in a particular state shall be treated as "Error" messages. All messages which do not change the state shall be treated as "Non-triggering or Informational" messages. All messages which expect a change in state shall be treated as "Triggering" messages. For each state, there should be guidelines that classify all possible messages into the above three categories. D.7. Security: A simple security scheme should be enabled in the IWF. In this scheme the IWF will accept requests from a pre-configured set of SIP Server, SIP EP, H.323 EP, or H.323 GKs only and it will reject all other requests. References [1] S. Bradner, "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [2] S. Bradner,"Key words for use in RFCs to indicate requirement levels", RFC 2119,IETF, March 1997. [3] M. Handley, H.Schulzrinne, E.Schooler, and J.Rosenberg, "SIP:Session Initiation Prtocol", RFC 2543,IETF,March 1999. [4] M. Handley and V. Jacobson, "SDP: Session Description Prtocol", RFC 2327, IETF, April 1998. [5] "Packet based multimedia communication systems", Recommendation H.323 Version 2,ITU-T,Geneva,Switzerland,Feb. 1998. [6] J.Rosenberg and H.Salama, "Usage of TRIP in Gateways for Exporting Agarwal, et al. [Page 149] Internet Draft SIP-H.323 Interworking February 2001 Phone Routes",draft-rs-trip-gw-00.txt, IETF, March 2000. Work in progress. [7] S. Donovan, "The SIP INFO Method," RFC 2976, IETF, Oct.2000. [8] Singh/Schulzrinne, "Interworking Between SIP/SDP and H.323", draft- singh-sip-h323-00.txt,IETF, January 2000. Work in progress. [9] H.Agrawal, R.R.Roy, V.Palawat, A.Johnston, C.Agboh, D.Wang, K.Singh and H.Schulzrinne, "SIP-H.323 Interworking Requirements",draft- agrawal-sip-h323-interworking-reqs-01.txt", IETF, Jan 2001. Work in progress. [10] H.Schulzrinne and S. Petrack, "RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals", RFC 2833, IETF, May 2000. [11] G. Camarillo and A. Roach, "Best Current Practice for ISUP to SIP mapping" Internet Draft, Work in Progress, March 2000. [12] "Call Signaling Protocols and Media Stream Packetization for Packet Based Multimedia Communications Systems " Recommendation H.225.0 Version 2, ITU-T, Geneva, Switzerland, March 1997. [13] "Control protocol for multimedia communication, " Recommendation H.245.0 Version 3, ITU-T, Geneva, Switzerland, Feb. 1998. Acknowledgments The authors would like to acknowledge the many contributors who debated the SIP-H.323 interworking architecture and requirements on the IETF, SIP and SG16 mailing lists. In particular, we would like to thank Dave Walker (SS8 Networks) and Jean-Francois Mule(Clarent Corporation). Contributions to this document have also been made through different internet-drafts and discussions with members of SIP, H.323, aHIT!, TIPHON and SG16 forums. Agarwal, et al. [Page 150] Internet Draft SIP-H.323 Interworking February 2001 Authors' Addresses Hemant Agrawal GlobeSpan Inc. A-8, Sector 9, Noida, UP - 201301 INDIA Tel: + 91-120-454-4028 x 121 Fax: + 91-120-454-4014 Email: hemantag@globespan.net Radhika R. Roy AT&T Room D3-2C09 200 Laurel Avenue S. Middletown, NJ 07748, USA Tel: + 1-732-420=1580 Fax: + 1-732-368-1302 Email: rrroy@att.com Vipin Palawat Cisco Systems Inc. 900, Chelmsford Street Tower II, Floor 14 Lowell, MA 01851 Tel: + 1-978-275-5122 Fax: + 1-978-275-5122 Email : vpalawat@cisco.com David Wang Nuera Communications Inc. 10445 Pacific Center Court San Diego, CA 92121 USA Tel: + 1-858-625-9220 x 1260 Fax: + 1-858-625-2422 Agarwal, et al. [Page 151] Internet Draft SIP-H.323 Interworking February 2001 Email: dwang@nuera.com Alan Johnston MCI WorldCom 100 South Fourth Street St. Louis, MO 63102 USA Tel: + 1-314- 3427360 Fax: + 1-314-3428452 Email: alan.johnston@wcom.com Charles Agboh Ebone Terhulsesteenweg 6A, 1560 Hoeilaart Belgium. Tel: + 22-658-4243 Fax: + 22-658-5118 Email: Charles.Agboh@ebone.com Kundan Singh Dept. of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027 USA Email: kns10@cs.columbia.edu Henning Schulzrinne Dept. of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027 USA Email: schulzrinne@cs.columbia.edu Joon Maeng VTel Communications 108 Wild Basin Rd. Agarwal, et al. [Page 152] Internet Draft SIP-H.323 Interworking February 2001 Austin, TX 78746 USA Tel: +1-512-437-4567 Email: joon_maeng@vtel.com Full Copyright Statement "Copyright (C) The Internet Society (date). All Rights Reserved. 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