Internet Engineering Task Force M. HASEBE Internet-Draft NTT-East Expiration: Aug 27th, 2006 J. KOSHIKO NTT-East Y. SUZUKI NTT-East T. YOSHIKAWA NTT-East Aug 27th, 2006 Examples call flow in race condition on Session Initiation Protocol draft-hasebe-sipping-race-examples-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document gives examples of Session Initiation Protocol (SIP) call flows in race condition. Call flows in race conditions are confusing and this document shows the best practices to handle them. The elements in these call flows include SIP User Agents and SIP Proxies. Call flow diagrams and message details are shown. Hasebe [Page 1] Internet Draft Examples call flow in race condition Aug 27th,2006 Table of Contents 1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 General Assumptions. . . . . . . . . . . . . . . . . . . . . 3 1.2 Legend for Message Flows . . . . . . . . . . . . . . . . . . 3 1.3 SIP Protocol Assumptions . . . . . . . . . . . . . . . . . . 4 2. The Dialog State Machine(for Race Condition) . . . . . . . . . . 4 3. Race condition . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1 Receiving message in the Moratorium State. . . . . . . . . . 8 3.1.1 Receiving Initial INVITE retransmission(Trying state). . 8 (old name: Initial INVITE retransmission) 3.1.2 Receiving CANCEL(Trying state) . . . . . . . . . . . . 11 (old name: CANCEL crossover) 3.1.3 Receiving CANCEL(Trying state) via a stateful proxy. . 14 (old name: CANCEL crossover via a stateful proxy) 3.1.4 Receiving BYE (Early state). . . . . . . . . . . . . . 21 (old name: BYE crossover on the early dialog) 3.1.5 Receiving re-INVITE (Established state). . . . . . . . 23 (old name: re-INVITE on the moratorium dialog) 3.1.6 Receiving BYE (Established state). . . . . . . . . . . 27 (old name: A retransmitted 200 OK after sending a BYE) 3.2 Receiving message in the Mortal State. . . . . . . . . . . 31 3.2.1 Receiving BYE(Established state) . . . . . . . . . . . 31 (old name: BYE crossover) 3.2.2 Receiving re-INVITE(Established state) . . . . . . . . 35 (old name: Session timer crossover (re-INVITE, BYE) ) 3.2.3 Receiving REFER(Established state) . . . . . . . . . . 39 (old name: REFER crossover (REFER, BYE) ) 3.2.4 Receiving 200OK for re-INVITE(Established state) . . . 43 (old name: A BYE is sent immediately after sending of a re-INVITE ) 3.2.5 Receiving ACK (Moratorium state) . . . . . . . . . . . 46 3.3 other race condition . . . . . . . . . . . . . . . . . . . 49 3.3.1 Early Dialog . . . . . . . . . . . . . . . . . . . . . 49 3.3.2 A BYE on the early dialog. . . . . . . . . . . . . . . 57 3.3.3 re-INVITE crossover. . . . . . . . . . . . . . . . . . 60 3.3.4 UPDATE and re-INVITE crossover . . . . . . . . . . . . 67 4. References . . . . . . . . . . . . . . . . . . . . . . . . . . 73 5. Intellectual Property Statement. . . . . . . . . . . . . . . . 74 6. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 74 1. Overview The call flows shown in this document were derived in the design of a SIP IP communications network. These examples are difficult to interpret the behaviors of user agent based on RFCs. In various situations which may happen when SIP is implemented, especially, when a situation which serves as a norm of implementing in RFC is not illustrated, by showing operation of a terminal or a server Hasebe [Page 2] Internet Draft Examples call flow in race condition Aug 27th,2006 as an example, it will be a help to a SIP implementors. For example, the sequence which CANCEL and 200 OK for INVITE cross each other is possible. INVITE transaction obviously exists from UAC's point of view, when the UAC sends a CANCEL message. However, when the UAS sends a 200 OK response for INVITE and then receives CANCEL message, there is not INVITE transaction anymore from UAS's point of view. In such a case, it's not easy to specify the response from the UAS in RFCs. This document clarifies SIP UA behaviors when messages cross each other as race conditions. By clarifying operation under race conditions, different interpretations between implementations are avoided and interoperability is expected to be promoted. It is the hope of the authors that this document will be useful for SIP implementors, designers, and protocol researchers and will help them achieve the goal of a standard implementation of RFC 3261 [1]. These call flows are based on the current version 2.0 of SIP in RFC 3261 [1] with SDP usage described in RFC 3264 [2]. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14, RFC 2119 [4]. 1.1 General Assumptions A number of architecture, network, and protocol assumptions underlie the call flows in this document. Note that these assumptions are not requirements. They are outlined in this section so that they may be taken into consideration and help in understanding of the call flow examples. These flows do not assume specific underlying transport protocols such as TCP, TLS, and UDP. See the discussion in RFC 3261 for details on the transport issues for SIP. 1.2 Legend for Message Flows Dashed lines (---) and slash lines (/,\) represent signaling messages that are mandatory to the call scenario.(X) represents crossover of signaling messages. Arrow indicate the direction of message flow. Double dashed lines (===) represent media paths between network elements. Messages with parentheses around their name represent optional Hasebe [Page 3] Internet Draft Examples call flow in race condition Aug 27th,2006 messages. Messages are identified in the Figures as F1, F2, etc. These numbers are used for references to the message details that follow the Figure. Comments in the message details are shown in the following form: /* Comments. */ 1.3 SIP Protocol Assumptions This document does not prescribe the flows precisely as they are shown, but rather illustrates the principles for best practice. They are best practice usages (orderings, syntax, selection of features for the purpose, or handling of error) of SIP methods, headers and parameters. NOTE: The flows in this document must not be copied as they are by implementors because additional characteristics were incorporated into the document for ease of explanation. To sum up, the procedures described in this document represent well-reviewed examples of SIP usage, which are best common practice according to IETF consensus. For simplicity in reading and editing the document, there are a number of differences between some of the examples and actual SIP messages. Examples are: Call-IDs are often repeated; CSeq often begins, at 1; header fields are usually shown in the same order; usually only the minimum required header field set is shown; and and Accept, Allow, etc are not shown. Actors: Element Display Name URI IP Address ------- ------------ --- ---------- User Agent Alice sip:alice@atlanta.example.com 192.0.2.101 User Agent Bob sip:bob@biloxi.example.com 192.0.2.201 User Agent Carol sip:carol@chicago.example.com 192.0.2.202 Proxy Server ss.atlanta.example.com 192.0.2.111 2. The Dialog State Machine(for Race Condition) Race conditions are generated when the dialog state of the receiving side differs from the dialog state of the sending side. Thus race conditions are generated on both UAs when caller's signal and callee's signal are intersected in the network. For instance, a race condition occurs when UAC (User Agent Client) sends a CANCEL on Early state while UAS (User Agent Server) is transitting from Early state to Confirmed state by sending a Hasebe [Page 4] Internet Draft Examples call flow in race condition Aug 27th,2006 200 OK to ini-INVITE. The dialog state machine (DSM) is represented as follows to help the understanding of UA's behavior in such race conditions. +-----------------------------------------------+ | Preparative | | +-----------+ +---------------+ | | | | 1xx-notag | |---C--+ | | Trying |---------->| Proceeding | | | 1xx-notag | | | | |<--C--+ | +-----------+ +---------------+ | | | +-----------------------------------------------+ | | | | 3xx-6xx | 1xx-tag | 2xx | | | | V | | +-------------------+ | | 3xx-6xx| |---+ | +<--------| Early | | 1xx-tag | | | |<--+ | | +-------------------+ | | | | | | | BYE | 2xx | | | +----------+----+ | | | +-----C------------C-----+ +-----------C-------+ | | Terminated | | | Confirmed | | | | +<----C-------| | | | | | | BYE | | | | | V | | V | | | +------------+ | | +-----------+ | | | | |---C-+ | | |---C--+ | | | Mortal | | | BYE | | Moratorium| | | 2xx | | | |<--C-+ | | |<--C--+ | | +------------+ | | +-----------+ | | | | | | | | | | | Timeout | | | ACK | | | | | | | | | V V | | V | | +---------------+ | | +-----------+ | | | | | | | | | | | Morgue | | | |Established| | | | | | | | | | | +---------------+ | | +-----------+ | | | | | +------------------------+ +-------------------+ figure 1 Hasebe [Page 5] Internet Draft Examples call flow in race condition Aug 27th,2006 Figure 1 shows a DSM for race conditions. This document clarifies UA's behavior by subdividing some internal states showed on FSM (Finate State Machine) for dialog state of the dialog-package[7], without changing the states of the dialog, "early", "confirmed", and "terminated" shown in RFC3261. Preparative state is put before the Ealy state, which includes Trying and Proceeding. Moreover, Confirmed state is devided into two sub-states, Moratorium and Established. In addition, Terminated state is subdivided into two states, Mortal and Morgue. The following is UA's behaviors in each state. Preparative: Preparative is a state until the Early dialog is established by sending and receiving a provisional response with To-tag after an ini-INVITE is sent and received. The dialog has not existed yet in Preparative state. The dialog state transit from the Preparative to the Early by sending or receiving a provisional response with To-tag. Moreover, the dialog state transit to Moratorium which is a substate of Confirmed state, if UA sends or receives a 2xx response. In addition, the dialog state transit to Morgue state which is a substate of Terminated state, if UA sends or receives a 3xx-6xx response. Sending an ACK to a 3xx-6xx response and retransmissions of 3xx-6xx are not expressed on this DSM because they are sent by INVITE transactions. Trying: Trying is substate of Preparative and inherits the behavior of Preparative. Trying is started by sending and receiving an ini-INVITE. It transits to Proceeding by sending or receiving a 1xx (usually 100 trying) without To-tag. UAC may retransmit an INVITE on transaction layer and UAC must not send a CANCEL request. UAS may send a 1xx-6xx response. Proceeding: Proceeding is substate of Preparative and inherits the behavior of Preparative. Dialog becomes Proceeding state if dialogs in Trying state send or receive a 1xx without To-tag (usually 100 trying). UAC may send a CANCEL, and UAS may send a 1xx-6xx response in Proceeding state. Early: The early dialog is established by sending or receiving a provisional response with To-tag. The early dialog exists though the dialog has not existed in this state yet. The dialog state transits from Early to Moratorium, substate of Confirmed by sending or receiving a 2xx response. In addition, the dialog state transits to the Morgue subdivided internally in the Terminated by sending and receiving a 3xx-6xx response. Hasebe [Page 6] Internet Draft Examples call flow in race condition Aug 27th,2006 Sending an ACK to a 3xx-6xx response and retransmissions of 3xx-6xx are not expressed on this DSM because they are sent by INVITE transactions. UAC may send CANCEL in Proceeding state. UAC may send BYE (although it is not recommended.) UAS may send a 1xx-6xx response. Confirmed: Sending or receiving 2xx final response establishes a dialog. Dialog exists in this state. BYE message changes state from Confirmed to Mortal, substate of Terminated. Confirmed has two substates, Moratorium and Established, they are different in messages UA are allowed to send. Moratorium: Moratorium is a substate of Confirmed and inherits the behavior of Confirmed. Moratorium transits to Established by sending or receiving an ACK request. UAC may send an ACK and UAS may send a 2xx final response. Established: Established is a substate of Confirmed and inherits the behavior of Confirmed. Both caller and callee may send various messages which influences a dialog. Caller supports the transmission of ACK to a retransmission of a 2xx response to an ini-INVITE. Terminated: Terminated state is devided into two substates, Mortal and Morgue, to consider a behavior when a dialog is being terminated. In this state, UAs hold information about the dialog which is being terminated. Confirmed transits to Mortal, a substate of Terminated, by sending or receiving a BYE request. Mortal: Caller and callee becomes Mortal state by sending or receiving a BYE. Only a BYE or its response can be handled in this state, and no other messages can be received. This is because the use case is taken into consideration that a BYE message are sent by both a caller and a callee to exchange reports about the session when it is being terminated. Therefore, UA possesses dialog information for internal process but dialog shouldn't exist outwardly. UA stops managing dialog state and changes it to Morgue state, when the BYE transaction is done by timer. (Timer F or Timer K for UAC. Timer J for UAS.) Morgue: Dialog doesn't exist any more in this state. Sending or receiving a signal which influences a dialog is not performed. (It is literally terminated.) 3. Race condition This section details race condition between two SIP User Agents (UAs): Alice and Bob. Alice (sip:alice@atlanta.example.com) Hasebe [Page 7] Internet Draft Examples call flow in race condition Aug 27th,2006 and Bob (sip:bob@biloxi.example.com) are assumed to be SIP phones or SIP-enabled devices. In case that CANCEL and 200 OK to INVITE intersect, INVITE transaction obviously exists in UAC. On the other side, there is not INVITE transaction anymore in UAS when it sends a 200 OK response to the INVITE and then receives a CANCEL request. This is an example of UA's behavior in Moratorium state, a substate of Confirmed. Examples of such race conditions are shown below. 3.1 Receiving message in the Moratorium State This section shows some examples of call flow in race condition when receiving the message from other states in the Moratorium state. 3.1.1 Receiving Initial INVITE retransmission(Trying state) in Moratorium state Alice Bob | | | ini-INVITE F1 | |------------------------------->| | 180 F2(Packet loss) | | X<---------------------| | | | ini-INVITE F4 200 F3 | |------------- --------------| Terminate(ServerTransaction) | \ / | | X | | / \ | |<------------ ------------->| | ACK F5 | |------------------------------->| | | | | In this scenario, all provisional responses to the initial INVITE (ini-INVITE) are lost, and UAC retransmits an ini-INVITE. At the same time as retransmission, UAS generates a 200 OK to the ini-INVITE and it terminate an INVITE server transaction. (RFC3261, 13.3.1.4) After sending a 200 OK, a TU of UAS processes ACK and retransmission of 200 OK. (RFC3261, 17.1) A TU of UAS processes a retransmitted ini-INVITE, but it doesn't have a To-tag, therefore the TU cannot use a mechanism to recognize the dialog by From-tag, Call-ID and To-tag. However, it must recognize a retransmitted ini-INVITE correctly by From-tag and Call-ID. (It must not construct a new dialog in response to a retransmitted Hasebe [Page 8] Internet Draft Examples call flow in race condition Aug 27th,2006 ini-INVITE regarding it as a request outside dialog.) Since TU of UAS retransmits a 200 OK according to the timer during it waits for ACK, it doesn't need to retransmit 200 OK for the retransmitted ini-INVITE. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 /* A 180 response is lost and does not reach Alice. */ F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Hasebe [Page 9] Internet Draft Examples call flow in race condition Aug 27th,2006 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Bob sends a 200 OK and terminates the INVITE transaction at the same time. TU performs retransmitting of a 200 OK directly.*/ F4 INVITE(retransmission) Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Since F2 is lost, Alice retransmits an ini-INVITE. The retransmitted INVITE does not match any existing transaction because Bob has already sent a 200 OK. Moreover, the retransmitted ini-INVITE does not have a To-tag, so it doesn't match any existing dialog. Therefore, Bob have to recognize the retransmitted INVITE correctly, without treating with the new INVITE. */ Hasebe [Page 10] Internet Draft Examples call flow in race condition Aug 27th,2006 F5 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 3.1.2 Receiving CANCEL(Trying state) in Moratorium state Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | |CANCEL F3 200 OK F4 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | | | ACK F6 481 F5 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | | | Both Way RTP Media | |<======================>| | BYE F7 | |----------------------->| | 200 F8 | |<-----------------------| | | | | In this scenario, Alice sends a CANCEL and Bob sends a 200 OK response to the initial INVITE message at the same time. Then Bob sends a 481 response in response to the CANCEL from Alice. UAC can terminate the session by sending a BYE immediately after receiving 200 OK for INVITE. Hasebe [Page 11] Internet Draft Examples call flow in race condition Aug 27th,2006 By transmitting a BYE after 200 OK, "it just means that the software in his phone needs to maintain state for a short while in order to clean up properly." (RFC3261, 15) In this sequence, it is recommended that caller terminates the session by sending a BYE. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 CANCEL Alice -> Bob CANCEL sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Hasebe [Page 12] Internet Draft Examples call flow in race condition Aug 27th,2006 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 /* When Alice sends a CANCEL, INVITE transaction exists. */ F4 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Alice sends a CANCEL and Bob sends a 200 OK response to the initial INVITE message at the same time. From Bob's point of view, an INVITE transaction is completed by sending of the final response (200 OK). A 200 OK and a CANCEL crossed each other and inconsistency has arisen in the state of INVITE transaction of Alice and Bob. */ F5 481 Call/Transaction Dose Not Exist Bob -> Alice SIP/2.0 481 Call/Transaction Dose Not Exist Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 CANCEL Contact: Content-Length: 0 /* The final respons to INVITE transaction has already sent while Hasebe [Page 13] Internet Draft Examples call flow in race condition Aug 27th,2006 CANCEL request targeting this INVITE transaction is received, so Bob returns a 481 response. */ F6 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* Bob has sent the final response, and a CANCEL becomes invalid. RTP streams are established.*/ F7 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F8 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 3.1.3 Receiving CANCEL(Trying state) via a stateful proxy in Moratorium state Alice Proxy Bob | | | | INVITE F1 | | Hasebe [Page 14] Internet Draft Examples call flow in race condition Aug 27th,2006 |--------------------->| INVITE F2 | | 100 Trying F3 |--------------------->| |<---------------------| 180 Ringing F4 | | 180 F5 |<---------------------| |<---------------------| | | | | | CANCEL F6 | | |--------------------->| CANCEL F7 200 F8 | | 200(CANCEL) F9 |--------- --------| |<---------------------| \ / | | | X | | | / \ | | 200(INVITE) F10 |<-------- ------->| |<---------------------| 481(CANCEL) F11 | | ACK F12 |<---------------------| |--------------------->| ACK F13 | | |--------------------->| | BYE F14 | | |--------------------->| BYE F15 | | |--------------------->| | | 200 F16 | | 200 F17 |<---------------------| |<---------------------| | | | | | | | If a CANCEL crosses a 200 OK to an INVITE between Bob and a stateful proxy, the UAC may receive a 200 OK to the INVITE after receiving 200 OK to the CANCEL. TU must manage a CANCEL transaction and an INVITE transaction independently, and even if a CANCEL is successful, TU cannot terminate an INVITE transaction, as described on 9.1 of RFC3261. Like "3.1.2 Receiving CANCEL(Trying state)", the UAC may send a BYE and terminate the session immediately after receiving 200 OK to an INVITE. Message Details F1 INVITE Alice -> Proxy INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 Hasebe [Page 15] Internet Draft Examples call flow in race condition Aug 27th,2006 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 INVITE Proxy -> Bob INVITE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Max-Forwards: 69 Record-Route: From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F3 100 Trying Proxy -> Alice SIP/2.0 100 Trying Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F4 180 Ringing Bob -> Proxy SIP/2.0 180 Ringing Hasebe [Page 16] Internet Draft Examples call flow in race condition Aug 27th,2006 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 ;received=192.0.2.233 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F5 180 Ringing Proxy -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F6 CANCEL Alice -> Proxy CANCEL sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 F7 CANCEL Proxy -> Bob CANCEL sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 /* Proxy sent a 200 OK to the CANCEL and Bob sent INVITE at the same time. */ Hasebe [Page 17] Internet Draft Examples call flow in race condition Aug 27th,2006 F8 200 OK(INVITE) Bob -> Proxy SIP/2.0 200 OK Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 ;received=192.0.2.233 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 148 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.100 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F9 200 OK(CANCEL) Proxy -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 /* Since CANCEL requests are hop-by-hop, the proxy answers with a 200 OK to the CANCEL of Alice. Note that the 200 OK doesn't mean the success of the CANCEL to the INVITE. */ F10 200 OK(INVITE) Proxy -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Hasebe [Page 18] Internet Draft Examples call flow in race condition Aug 27th,2006 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 148 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.100 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F11 481 Call/Transaction Does Not Exist Bob -> Proxy SIP/2.0 481 Call/Transaction Does Not Exist Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 /* Since Bob has already sent 200 OK to INVITE, CANCEL fails with 481 response. */ F12 ACK Alice -> Proxy ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bq9 Max-Forwards: 70 Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F13 ACK Proxy -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bq9 ;received=192.0.2.101 Max-Forwards: 69 From: Alice ;tag=9fxced76sl Hasebe [Page 19] Internet Draft Examples call flow in race condition Aug 27th,2006 To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F14 BYE Alice -> Proxy BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74be5 Max-Forwards: 70 Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Alice may send a BYE and terminate the sessin immediately on receipt of a 200 OK after the CANCEL. */ F15 BYE Proxy -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK739578.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74be5 ;received=192.0.2.101 Max-Forwards: 69 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F16 200 OK Bob -> Proxy SIP/2.0 200 OK Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK739578.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74be5 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F17 200 OK Proxy -> Alice Hasebe [Page 20] Internet Draft Examples call flow in race condition Aug 27th,2006 SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74be5 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 BYE Content-Length: 0 3.1.4 Receiving BYE (Early state) in Moratorium state Alice Bob | | | ini-INVITE F1 | |------------------------------->| | 180 F2 | |<-------------------------------| | | | BYE F4 200(INVITE) F3| |------------- --------------| | \ / | | X | | / \ | |<------------ ------------->| | | | 200(BYE) F5 | |<-------------------------------| | | | | In this scenario, Alice sends a BYE on the early dialog and Bob sends a 200 OK response to the initial INVITE message at the same time. Bob receives a BYE on the Confirmed dialog though Alice sended a BYE on the Early dialog. A BYE functions normally even if it is received after the INVITE transaction terminates because a BYE differs from a CANCEL, and is sent to not request but the dialog. Alice gets into a Mortal state on receiving the BYE response, and remains Mortal until the Timer K timeout occurs. Therefore, UA don't send an ACK if it receives a 200 to INVITE. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Hasebe [Page 21] Internet Draft Examples call flow in race condition Aug 27th,2006 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK(ini-INVITE) Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 Hasebe [Page 22] Internet Draft Examples call flow in race condition Aug 27th,2006 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 BYE Alice -> Bob BYE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F5 200 OK(BYE) Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Contact: Content-Length: 0 3.1.5 Receiving re-INVITE (Established state) in Moratorium state Alice Bob | | | ini-INVITE F1 | |------------------------------->| | 180 F2 | |<-------------------------------| | | | 200 F3 | |<-------------------------------| | ACK F4(packet loss) | |-------------------->X | | | | re-INVITE F6 200 F5 | |------------- --------------| | \ / | | X | | / \ | |<------------ ------------->| | ACK F7 200 F8 | |------------- --------------| Hasebe [Page 23] Internet Draft Examples call flow in race condition Aug 27th,2006 | \ / | | X | | / \ | |<------------ ------------->| | ACK F9 | |------------------------------->| | | | | In this scenario, UAS receives a re-INVITE before receiving an ACK to ini-INVITE. UAS sends a 200 OK to the re-INVITE (F8) because it has sent a 200 OK to the ini-INVITE (F3, F5) and the dialog has already been confirmed. However, if a 200 OK to the ini-INVITE has an offer and the answer would be in the ACK, UA should return by a 491 to the re-INVITE. If UAS doesn't receive an ACK for a long time, it should send a BYE and terminate the dialog. Editor's Note: In this sequence, UAS comes to know that UAC receives a 200 OK to the ini-INVITE, when UAS receives a re-INVITE on the dialog. Therefore, it's believed that UA may view an ACK to be received already if it has received a mid-dialog request such as a re-INVITE even though it hasn't actually received an ACK. (However, only provided an ACK plays a role to transmit that UAC receives the 200 OK. In other words, in case that an ACK doesn't have an answer. ) It is a difficult problem if UAS in Moratorium state accepts the message generated by Established state. Therefore, this example may be corrected. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 Hasebe [Page 24] Internet Draft Examples call flow in race condition Aug 27th,2006 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Hasebe [Page 25] Internet Draft Examples call flow in race condition Aug 27th,2006 Content-Length: 0 /* A ACK request is lost. */ F5 200 OK Bob -> Alice (retransmission) SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* UAS retransmits a 200 OK to an ini-INVITE since it didn't receive a ACK. */ F6 re-INVITE Alice -> Bob INVITE sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Length: 151 v=0 o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly Hasebe [Page 26] Internet Draft Examples call flow in race condition Aug 27th,2006 F7 ACK Alice -> Bob (retransmission) ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F8 200 OK(re-INVITE) Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Length: 151 v=0 o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=recvonly F9 ACK Alice -> Bob ACK sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK230f2.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 ACK Content-Length: 0 3.1.6 Receiving BYE (Established state) in Moratorium state Hasebe [Page 27] Internet Draft Examples call flow in race condition Aug 27th,2006 Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4(packet loss) | |-------------->X | | Both Way RTP Media | |<======================>| | BYE F6 200 F5 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | 200 OK F7 | |<-----------------------| | | | | In this scenario, a ACK request to a 200 OK response is lost (or delay), immediately after Bob sends the retransmitted 200 OK to ini-INVITE and Alice sends a BYE at the same time. Depending on the implement of a SIP user agent, Alice may start a session again by reception of the retransmitted 200 OK with SDP since she has already terminated a session by sending a BYE. In that case, if UAC receives a retransmitted 200 OK after sending a BYE, you should not start a session again since the session which is not associated with dialog remains. Moreover, in the case where UAS sends an offer with a 200 OK, if UAS receives a retransmitted ACK after receiving a BYE, UAS should not start a session again for the same reason. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com Hasebe [Page 28] Internet Draft Examples call flow in race condition Aug 27th,2006 CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob Hasebe [Page 29] Internet Draft Examples call flow in race condition Aug 27th,2006 ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* A ACK request is lost. */ F5 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* UAS retransmits a 200 OK to an ini-INVITE since it didn't receive a ACK. */ F6 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Bob retransmits a 200 OK and Alice sends a BYE at the same time. */ Hasebe [Page 30] Internet Draft Examples call flow in race condition Aug 27th,2006 F7 200 OK(BYE) Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Bob sends a 200 OK to a BYE. */ Editor's Note In the old version, Alice responds with an ACK when she have sent an ACK to the first 200 OK once. However, this version was modified that TU don't send an ACK to the retransmited 200 because TU understands oneself is in Mortal state. 3.2 Receiving message in the Mortal State This section shows some examples of call flow in race condition when receiving the message from other states in the Mortal state. 3.2.1 Receiving BYE(Establish state) in Mortal state Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4 | |----------------------->| | Both Way RTP Media | |<======================>| | | | BYE F5 BYE F6 | |--------- ----------| | \ / | | X | | / \ | Hasebe [Page 31] Internet Draft Examples call flow in race condition Aug 27th,2006 |<-------- --------->| | | | 200 F8 200 F7 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | | | | In this scenario, Alice and Bob send a BYE at the same time. A session is ended shortly after a BYE request is passed to a client transaction. According to 15.1.1 of RFC3261, a dialog seems to be completed by a response or timeout of a BYE. As shown in section 2, UA remains in Mortal state after sending a BYE until sending a BYE to actually terminating the dialog. (Any requests or responses which influence dialogs or sessions are invalid even though the dialog exists.) UAs in Mortal state return error responses to the requests that operate dialog or session, such as re-INVITE, or REFER. Exception is a BYE message. UA shall return 200 OK to the BYE because it can give the dialog in Mortal State a finishing stroke and send it to the Morgue. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 Hasebe [Page 32] Internet Draft Examples call flow in race condition Aug 27th,2006 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ /* Bob hangs up. Note that the CSeq is NOT 2, since Alice and Bob maintain their own independent CSeq counts. Hasebe [Page 33] Internet Draft Examples call flow in race condition Aug 27th,2006 (The INVITE was request 1 generated by Alice, and the BYE is request 1 generated by Bob) */ F5 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* The session is terminated at the moment Alice sends a BYE. The dialog still exists then, but it is certain to be terminated in a short period of time. The dialog is completely terminated when the timeout of the BYE request occurs. */ F6 BYE Bob -> Alice BYE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 BYE Content-Length: 0 /* Bob has also transmitted a BYE simultaneously with Alice. Bob terminates a session and a dialog. */ F7 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 ;received=192.0.2.201 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Since the dialog is Moratorium state, Bob responds with a 200 to the BYE. */ Hasebe [Page 34] Internet Draft Examples call flow in race condition Aug 27th,2006 Editor's Note: In the old version, UA sends a 481 since the dialog is terminated by sending a BYE request. (draft-hasebe-sipping-exceptional-procedure-example-02.txt) In this draft, UA's behavior in the example is modified to return 200 OK. It is an advantage of returning of 200 over 481 that information when the dialog is terminated can be passed on by the BYE response. F8 200 OK Alice -> Bob SIP/2.0 200 OK Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 ;received=192.0.2.201 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 BYE Content-Length: 0 /* Since Alice has transited from the established state to Mortal state by sending a BYE, Alice responds with a 200 to a BYE. */ 3.2.2 Receiving re-INVITE(Establish state) in Mortal state Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4 | |----------------------->| | Both Way RTP Media | |<======================>| | | | BYE F5 re-INVITE F6| |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | | Hasebe [Page 35] Internet Draft Examples call flow in race condition Aug 27th,2006 | 481 F8 200 F7 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | ACK F9 | |<-----------------------| | | In this scenario, Bob sends a re-INVITE, and Alice sends a BYE at the same time. The re-INVITE of Bob is returned by a 481, since TU of Alice has transited from Established state to Mortal state by sending a BYE. Bob sends an ACK to a 481 response, because a client transaction of a re-INVITE remains still. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl Hasebe [Page 36] Internet Draft Examples call flow in race condition Aug 27th,2006 To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* In this sequence, Bob sets refresher=uas since there was no specification of refresher. */ F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 BYE Alice -> Bob Hasebe [Page 37] Internet Draft Examples call flow in race condition Aug 27th,2006 BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Alice sends a BYE and terminates a session, and transits from the confirmed state to the terminnated state. */ F6 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 /* Alice sends a BYE, and Bob sends a re-INVITE at the same time. The state of dialog transits to Mortal state at the moment Alice sends a BYE, but Bob doesn't know it until he receives the BYE. Therefore, the dialog is Terminated state from Alice's point of view, but the dialog is Confirmed state from Bob's point of view. A race condition occurs. */ F7 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 ;received=192.0.2.201 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F8 481 Call/Transaction Does Not Exist Alice -> Bob SIP/2.0 481 Call/Transaction Does Not Exist Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Hasebe [Page 38] Internet Draft Examples call flow in race condition Aug 27th,2006 ;received=192.0.2.201 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 /* Since Alice is in Mortal state, she responds with a 481 to the re-INVITE. */ F9 ACK Bob -> Alice ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 3.2.3 Receiving REFER(Establish state) in Mortal state Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4 | |----------------------->| | Both Way RTP Media | |<======================>| | | | BYE F5 REFER F6 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | | | 481 F8 200 F7 | |--------- ----------| | \ / | | X | Hasebe [Page 39] Internet Draft Examples call flow in race condition Aug 27th,2006 | / \ | |<-------- --------->| | | | | In this scenario, Bob sends a REFER, and Alice sends a BYE at the same time. Bob send a REFER in the same dialog. Alice sends an error response to request like a REFER which operates the dialog (or session) , because Alice is in Mortal state by sending a BYE. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 Hasebe [Page 40] Internet Draft Examples call flow in race condition Aug 27th,2006 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 Hasebe [Page 41] Internet Draft Examples call flow in race condition Aug 27th,2006 /* Alice sends a BYE and terminates a session, and transits from Confirmed state to Terminnated state. */ F6 REFER Bob -> Alice REFER sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com Refer-To: sip:carol@cleveland.example.org Contact: CSeq: 1 REFER Content-Length: 0 /* Alice sends a BYE, and Bob sends a REFER at the same time. Bob sends a REFER on the INVITE dialog. The state of dialog transits to Mortal state at the moment Alice sends a BYE, but Bob doesn't know it until he receives the BYE. A race condition occurs. */ F7 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 F8 481 Call/Transaction Does Not Exist Alice -> Bob SIP/2.0 481 Call/Transaction Does Not Exist Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 ;received=192.0.2.201 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 REFER Content-Length: 0 /* Since Alice is in Mortal state, she responds with a 481 to the REFER. */ Hasebe [Page 42] Internet Draft Examples call flow in race condition Aug 27th,2006 3.2.4 Receiving 200OK for re-INVITE(Establish state) in Mortal state Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | 200 OK F3 | |<-----------------------| | ACK F4 | |----------------------->| | Both Way RTP Media | |<======================>| | | | re-INVITE F5 | |<-----------------------| | 200 F7 BYE F6 | |--------- ----------| | \ / | | X | | / \ | |<-------- --------->| | 200 OK F8 | |----------------------->| | | | | In this scenario, Bob sends a BYE immediately after sending a re-INVITE, (A user is not conscious that refresher sends a re-INVITE automatically. For example, in the case of a telephone application, it is possible that a user places a receiver immediately after refresher.) When Alice receives a BYE other than ACK,she stops retransmitting of 200 OK. Since ACK for 2xx responses is not a server transaction, it is that UAS core transmits directly. With UAS core, since the dialog which matches 200 OK received is terminated, 200 OK is ignored, without sending ACK. Message Details F1 INVITE Alice -> Bob Hasebe [Page 43] Internet Draft Examples call flow in race condition Aug 27th,2006 INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 Hasebe [Page 44] Internet Draft Examples call flow in race condition Aug 27th,2006 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F6 BYE Bob -> Alice BYE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Bob sends a BYE immediately after sending of a re-INVITE. Bob terminates a session and transits from Established state to Mortal state. */ Hasebe [Page 45] Internet Draft Examples call flow in race condition Aug 27th,2006 F7 200 OK(re-INVITE) Alice -> Bob SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds7 ;received=192.0.2.201 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 /* Bob sends a BYE, and Alice responds with a 200 OK to re-INVITE. A race condition occurs. */ F8 200 OK(BYE) Alice -> Bob SIP/2.0 200 OK Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds8 ;received=192.0.2.201 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* The UAC core of Bob does not send a ACK after receiving 200 OK to a re-INVITE.(Bob has terminated the dialog by sending of a BYE.) The UAS core of Alice does not retransmit 200 OK to a re-INVITE. (Since the dialog is terminated by reception of BYE, Alice does not retransmit 200 OK even if she does not receive ACK from Bob.) */ 3.2.5 Receiving ACK (Moratorium state) in Mortal state Alice Bob | | | ini-INVITE F1 | |------------------------------->| | 180 F2 | |<-------------------------------| | 200 F3 | |<-------------------------------| | | | ACK F4 BYE F5 | |------------- --------------| Hasebe [Page 46] Internet Draft Examples call flow in race condition Aug 27th,2006 | \ / | | X | | / \ | |<------------ ------------->| | 200 F6 | |------------------------------->| | | | | In this scenario, Alice sends an ACK and Bob sends a BYE at the same time. When the offer is in a 2xx, and the answer is in an ACK, this example is in a race condition. Do not begin the session by receiving an ACK because Bob has already terminated the session by sending the BYE. The answer of ACK is just ignored. F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com Hasebe [Page 47] Internet Draft Examples call flow in race condition Aug 27th,2006 CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Hasebe [Page 48] Internet Draft Examples call flow in race condition Aug 27th,2006 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Alice sends a BYE and terminates a session and dialog. */ F6 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds8 ;received=192.0.2.201 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 3.3 Other race condition Here, examples in race condition that doesn't relate directly to the dialog state transition are shown. In this section, it is shown that how to treat the race condition which generated when UAs treat "What is established by SIP" which related closely with dialog. 3.3.1 Early Dialog Alice Proxy Bob Carol | | | | | INVITE(sdp1) F1 | | | |--------------------->| INVITE(sdp1) F2 | | | 100 Trying F3 |--------------------->| | |<---------------------| 183(sdp2)To-tag=1 F4 | | | 183(sdp2)To-tag=1 F5 |<---------------------| | |<---------------------| | | | PRACK F6 | | | |--------------------->| PRACK F7 | | | |--------------------->| | | | 200(PRACK) F8 | | | 200(PRACK) F9 |<---------------------| | |<---------------------| | | |<=============Both Way RTP Media============>| | | | CANCEL F10 | | | |--------------------->| | | | 200(CANCEL) F11 | | | |<---------------------| | | | 487(INVITE) F12 | | | |<---------------------| | Hasebe [Page 49] Internet Draft Examples call flow in race condition Aug 27th,2006 | | ACK(INVITE) F13 | | | |--------------------->| | | | | | | | | | | INVITE(sdp1) F14 | | |---------------------------->| | | 180 To-tag=2 F15 | | 180 To-tag=2 F16 |<----------------------------| |<---------------------| | | | 200(sdp3)To-tag=2 F17 | | 200(sdp3)To-tag=2 F18|<----------------------------| |<---------------------| | | ACK F19 | | |--------------------->| ACK F20 | | |---------------------------->| |<================Both Way RTP Media================>| | | | | | | In this scenario, a proxy is forking to another address (Carol), if Bob don't return final response. When a proxy sends INVITEs to two or more addresses, two or more early dialogs may be established at UAC. At UAC, all early dialogs are released when the final response of ini-INVITE is received. (RFC3261, 13.2.2.4) Only the confirmed dialog continues after a 200 OK reception. Even if Bob is replaced by Media Server, you have the result appear to UAC just as this call flow. In this sequence, Bob can terminate the early media when he receives CANCEL, but Alice does not have the trigger to terminate the early dialog. When Bob stops sending RTP by the CANCEL from Proxy, it seems to Alice that RTP breaks off suddenly. Message Details F1 INVITE Alice -> Proxy INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Supported: 100rel Content-Type: application/sdp Content-Length: 151 Hasebe [Page 50] Internet Draft Examples call flow in race condition Aug 27th,2006 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 INVITE Proxy -> Bob INVITE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Max-Forwards: 69 Record-Route: From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Supported: 100rel Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F3 100 Trying Proxy -> Alice SIP/2.0 100 Trying Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F4 183 Session Progress Bob -> Proxy Hasebe [Page 51] Internet Draft Examples call flow in race condition Aug 27th,2006 SIP/2.0 183 Session Progress Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 ;received=192.0.2.233 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Require: 100rel Content-Type: application/sdp Content-Length: 148 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.100 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F5 183 Session Progress Proxy -> Alice SIP/2.0 183 Session Progress Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE RSeq: 1 Contact: Require: 100rel Content-Type: application/sdp Content-Length: 148 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.100 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Early dialog is established between Alice and Bob, and early media is also established at the same time. */ Hasebe [Page 52] Internet Draft Examples call flow in race condition Aug 27th,2006 F6 PRACK Alice -> Proxy PRACK sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Route: From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 PRACK RAck: 1 1 INVITE Content-Length: 0 F7 PRACK Proxy -> Bob PRACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 PRACK RAck: 1 1 INVITE Content-Length: 0 F8 200 OK(PRACK) Bob -> Proxy SIP/2.0 200 OK Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 PRACK Contact: Content-Length: 0 F9 200 OK(PRACK) Proxy -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 2 PRACK Content-Length: 0 Hasebe [Page 53] Internet Draft Examples call flow in race condition Aug 27th,2006 F10 CANCEL Proxy -> Bob CANCEL sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 /* The proxy cancels the INVITE to Bob, and sends an INVITE to Carol. Although the continuation of early media after CANCEL reception depends on the implementation of the user agent, Alice does not know that the proxy cancels the INVITE, therefore, when Bob stops early media after CANCEL reception, it seems to her that the sound stops suddenly. */ F11 200 OK(CANCEL) Bob -> Proxy SIP/2.0 200 OK Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.2 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 CANCEL Content-Length: 0 F12 487 Request Terminated(INVITE) Bob -> Proxy SIP/2.0 487 Request Terminated Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F13 ACK(INVITE) Proxy -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 From: Alice ;tag=9fxced76sl To: Bob ;tag=314159 Hasebe [Page 54] Internet Draft Examples call flow in race condition Aug 27th,2006 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F14 INVITE Proxy -> Carol INVITE sip:carol@client.chicago.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK83749a.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Max-Forwards: 69 Record-Route: From: Alice ;tag=9fxced76sl To: Bob Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Supported: 100rel Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F15 180 Ringing Carol -> Proxy SIP/2.0 180 Ringing Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK83749a.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content Length:0 F16 180 Ringing Proxy -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Hasebe [Page 55] Internet Draft Examples call flow in race condition Aug 27th,2006 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content Length:0 /* Proxy and Alice establish the second Early dialog when they receive a 180 response from Carol. */ F17 200 OK Carol -> Proxy SIP/2.0 200 OK Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK83749a.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content Length: 151 v=0 o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com s=Session SDP c=IN IP4 client.chicago.example.com t=3034423619 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F18 200 OK Proxy -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Record-Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 INVITE Contact: Content Length: 151 Hasebe [Page 56] Internet Draft Examples call flow in race condition Aug 27th,2006 v=0 o=carol 2890844922 2890844922 IN IP4 client.chicago.example.com s=Session SDP c=IN IP4 client.chicago.example.com t=3034423619 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* By 200 OK response, all early dialogs are terminated except for one that was confirmed. */ F19 ACK Alice -> Proxy ACK sip:carol@client.chicago.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bq9 Max-Forwards: 70 Route: From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F20 ACK Proxy -> Carol ACK sip:carol@client.chicago.example.com SIP/2.0 Via: SIP/2.0/UDP ss.atlanta.example.com:5060;branch=z9hG4bK721e.1 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bq9 ;received=192.0.2.101 Max-Forwards: 69 From: Alice ;tag=9fxced76sl To: Bob ;tag=456654 Call-ID: 2xTb9vxSit55XU7p8@atlanta.example.com CSeq: 1 ACK Content-Length: 0 3.3.2 A BYE on the early dialog Alice Bob | | | INVITE F1 | |----------------------->| | 180 Ringing F2 | |<-----------------------| | | | BYE F3 | Hasebe [Page 57] Internet Draft Examples call flow in race condition Aug 27th,2006 |----------------------->| | 200 OK(BYE) F4 | |<-----------------------| | 487 F5 | |<-----------------------| | ACK F6 | |----------------------->| | | | | In this scenario, Alice establishes an early dialog with the receiving 180 response. Alice sends a BYE on the early dialog. According to Section 15 of RFC3261, callee's UA MUST NOT send a BYE on early dialogs, but the caller's UA MAY send a BYE on early dialogs. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com Hasebe [Page 58] Internet Draft Examples call flow in race condition Aug 27th,2006 CSeq: 1 INVITE Contact: Content-Length: 0 /* Alice forms an early dialog by receiving a 180 response to ini-INVITE. However Bob is not sure that Alice received the 180 response. */ F3 BYE Alice -> Bob BYE sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Alice sends a BYE on the early dialog and Alice terminates a session (if any). */ F4 200 OK(BYE) Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bKnashds9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 BYE Content-Length: 0 /* Bob sends a 200 OK to a BYE of Alice, and Bob terminates a session (if any). */ F5 487 Request Terminated(INVITE) Bob -> Alice SIP/2.0 487 Request Terminated Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 Hasebe [Page 59] Internet Draft Examples call flow in race condition Aug 27th,2006 /* Bob should terminate the early dialog when he receives a BYE. Bob sends a 487 response to terminate a INVITE transaction in the similar way to handle a CANCEL from Alice, because the INVITE transaction remains after terminating the early dialog. */ F6 ACK Alice -> Bob ACK sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Contact: Content-Length: 0 /* Alice sends an ACK to a 487 response as processing of the ini-INVITE transaction. (The dialog has been already terminated, but the ini-INVITE transaction remains) */ 3.3.3 re-INVITE crossover Alice Bob | | | INVITE F1 | |--------------------------->| | 180 Ringing F2 | |<---------------------------| | | | 200 OK F3 | |<---------------------------| | ACK F4 | |--------------------------->| | Both Way RTP Media | |<==========================>| | | |re-INVITE F5 re-INVITE F6 | |------------ -------------| | \ / | | X | | / \ | |<----------- ------------>| | 491 F8 491 F7 | |------------ -------------| | \ / | | X | | / \ | Hasebe [Page 60] Internet Draft Examples call flow in race condition Aug 27th,2006 |<----------- ------------>| | ^ ACK F9 ^ ACK F10| |--|--------- ----|--------| | | \ / | | | | X | | | | / \ | | |<-|---------- ---|------->| | | | | | |0-2.0 sec | | | | | | | v re-INVITE F11 | | |<------------------|--------| | 200 OK F12 | | |-------------------|------->| | ACK F13 | | |<------------------|--------| | | | | |2.1-4.0 sec | | | | re-INVITE F14 v | |--------------------------->| | 200 OK F15 | |<---------------------------| | ACK F16 | |--------------------------->| | | | | In this scenario, Alice and Bob send a re-INVITE at the same time. When two re-INVITEs cross in the same dialog, they resend re-INVITEs after different intervals.(RFC3261, 14.1) When Alice sends an initial INVITE, an INVITE will be sent again after 2.1-4.0 seconds because she generated the Call-ID (owner of the Call-ID). Bob will send an INVITE again after 0.0-2.0 seconds, because Bob isn't the owner of the Call-ID. Therefore, each user agent must remember whether they has generated the Call-ID of the dialog or not, in case INVITEs may be crossed by another INVITE. Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl Hasebe [Page 61] Internet Draft Examples call flow in race condition Aug 27th,2006 To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 Hasebe [Page 62] Internet Draft Examples call flow in race condition Aug 27th,2006 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 re-INVITE Alice -> Bob INVITE sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Length: 151 v=0 o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly F6 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 Hasebe [Page 63] Internet Draft Examples call flow in race condition Aug 27th,2006 /* A case where a re-INVITE for a session refresh and a re-INVITE for hold are sent at the same time. */ F7 491 Request Pending Bob -> Alice SIP/2.0 491 Request Pending Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Length: 0 /* Since an INVITE is in progress, a 491 response are returned. */ F8 491 Request Pending Alice -> Bob SIP/2.0 491 Request Pending Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F9 ACK(INVITE) Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 ACK Content-Length: 0 F10 ACK(INVITE) Bob -> Alice ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 Hasebe [Page 64] Internet Draft Examples call flow in race condition Aug 27th,2006 F11 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7.1 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Since Bob is not the owner of Call-ID, Bob sends an INVITE again after 0.0-2.0 seconds. */ F12 200 OK Alice -> Bob SIP/2.0 200 OK Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7.1 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F13 ACK Bob -> Alice ACK sip:alice@client.atlanta.example.com SIP/2.0 Hasebe [Page 65] Internet Draft Examples call flow in race condition Aug 27th,2006 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bK74b44 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 ACK Content-Length: 0 F14 re-INVITE Alice -> Bob INVITE sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 3 INVITE Content-Length: 151 v=0 o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly /* Since Alice is the owner of Call-ID, Alice sends an INVITE again after 2.1-4.0 seconds. */ F15 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 3 INVITE Content-Length: 151 v=0 o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 Hasebe [Page 66] Internet Draft Examples call flow in race condition Aug 27th,2006 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=recvonly F16 ACK Alice -> Bob ACK sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK230f2.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 3 ACK Content-Length: 0 3.3.4 UPDATE and re-INVITE crossover Alice Bob | | | INVITE F1 | |--------------------------->| | 180 Ringing F2 | |<---------------------------| | | | 200 OK F3 | |<---------------------------| | ACK F4 | |--------------------------->| | Both Way RTP Media | |<==========================>| | | | UPDATE F5 re-INVITE F6 | |------------ -------------| | \ / | | X | | / \ | |<----------- ------------>| | 491 F8 491 F7 | |------------ -------------| | \ / | | X | | / \ | |<----------- ------------>| | ^ ACK F9 ^ | |--|----------------|------->| | | | | | |0-2.0 sec | | | | | | Hasebe [Page 67] Internet Draft Examples call flow in race condition Aug 27th,2006 | v re-INVITE F10 | | |<------------------|--------| | 200 OK F11 | | |-------------------|------->| | ACK F12 | | |<------------------|--------| | | | | |2.1-4.0 sec | | | | UPDATE F13 v | |--------------------------->| | 200 OK F14 | |<---------------------------| | | | | In this scenario, the UPDATE contains SDP offer, therefore UPDATE and re-INVITE are returned error response(491) as in the case of "re-INVITE crossover". When an UPDATE for refresher which doesn't contain a session description and the re-INVITE crossed each other, both request don't fail by 491 and succeed with 200 because 491 means that UA have a pending request. Moreover, the same is equally true of UPDATE crossover, in case that either UPDATE contains a session description fail with 491, other cases succeed with 200. Editor's Note: A 491 response is considered a result that UA judged the effectiveness of request to "What is established by SIP". Therefore, it is considered that 491 will be used in all the requests that demand operation to "What is established by SIP". Message Details F1 INVITE Alice -> Bob INVITE sip:bob@biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Supported: timer Session-Expires: 300 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 151 Hasebe [Page 68] Internet Draft Examples call flow in race condition Aug 27th,2006 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F2 180 Ringing Bob -> Alice SIP/2.0 180 Ringing Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Length: 0 F3 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 ;received=192.0.2.101 Require: timer Session-Expires: 300;refresher=uas From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Contact: Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F4 ACK Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Hasebe [Page 69] Internet Draft Examples call flow in race condition Aug 27th,2006 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bd5 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 /* RTP streams are established between Alice and Bob */ F5 UPDATE Alice -> Bob UPDATE sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 UPDATE Content-Length: 151 v=0 o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly F6 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 /* A case where a re-INVITE for a session refresh and a re-INVITE for hold are sent at the same time. */ F7 491 Request Pending Bob -> Alice Hasebe [Page 70] Internet Draft Examples call flow in race condition Aug 27th,2006 SIP/2.0 491 Request Pending Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 UPDATE Content-Length: 0 /* Since an INVITE is in process, a 491 response are returned. */ F8 491 Request Pending Alice -> Bob SIP/2.0 491 Request Pending Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 INVITE Content-Length: 0 F9 ACK(INVITE) Alice -> Bob ACK sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 1 ACK Content-Length: 0 F10 re-INVITE Bob -> Alice INVITE sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7.1 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Type: application/sdp Content-Length: 147 v=0 o=bob 2890844527 2890844527 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 Hasebe [Page 71] Internet Draft Examples call flow in race condition Aug 27th,2006 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 /* Since Bob is not the owner of Call-ID, Bob sends an INVITE again after 0.0-2.0 seconds. */ F11 200 OK Alice -> Bob SIP/2.0 200 OK Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bKnashds7.1 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 INVITE Content-Type: application/sdp Content-Length: 151 v=0 o=alice 2890844526 2890844526 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 F12 ACK Bob -> Alice ACK sip:alice@client.atlanta.example.com SIP/2.0 Via: SIP/2.0/UDP client.biloxi.example.com:5060;branch=z9hG4bK74b44 Session-Expires: 300;refresher=uac Max-Forwards: 70 From: Bob ;tag=8321234356 To: Alice ;tag=9fxced76sl Call-ID: 3848276298220188511@atlanta.example.com CSeq: 2 ACK Content-Length: 0 F13 UPDATE Alice -> Bob UPDATE sip:sip:bob@client.biloxi.example.com SIP/2.0 Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com Hasebe [Page 72] Internet Draft Examples call flow in race condition Aug 27th,2006 CSeq: 3 UPDATE Content-Length: 151 v=0 o=alice 2890844526 2890844527 IN IP4 client.atlanta.example.com s=- c=IN IP4 192.0.2.101 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=sendonly /* Since Alice is the owner of Call-ID, Alice sends an INVITE again after 2.1-4.0 seconds. */ F14 200 OK Bob -> Alice SIP/2.0 200 OK Via: SIP/2.0/UDP client.atlanta.example.com:5060;branch=z9hG4bK74bf9.1 Max-Forwards: 70 From: Alice ;tag=9fxced76sl To: Bob ;tag=8321234356 Call-ID: 3848276298220188511@atlanta.example.com CSeq: 3 INVITE Content-Length: 151 v=0 o=bob 2890844527 2890844528 IN IP4 client.biloxi.example.com s=- c=IN IP4 192.0.2.201 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 a=recvonly 4. References [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [2] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with SDP", RFC 3264, April 2002. [3] Johnston, A., Donovan, S., Sparks, R., Cunningham, C. and K. Summers, "Session Initiation Protocol (SIP) Basic Call Flow Examples", BCP 75, RFC 3665, December 2003. Hasebe [Page 73] Internet Draft Examples call flow in race condition Aug 27th,2006 [4] Johnston, A., Donovan, S., Sparks, R., Cunningham, C. and K. Summers, "Session Initiation Protocol (SIP) Public Switched Telephone Network (PSTN) Call Flows", BCP 76, RFC 3666, December 2003. [5] Sparks, R., "The Session Initiation Protocol (SIP) Refer Method", RFC 3515, April 2003. [6] Rosenberg, J. and H. Schulzrinne, "Reliability of Provisional Responses in the Session Initiation Protocol (SIP)", RFC 3262, June 2002. [7] Rosenberg, J., Schulzrinne, H., Mahy, R., "An INVITE-Initiated Dialog Event Package for the Session Initiation Protocol (SIP)", RFC 4235, November 2005. 5. Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. 6. Authors' Addresses All listed authors actively contributed large amounts of text to this document. Miki Hasebe NTT-east Corporation 19-2 Nishi-shinjuku 3-chome Shinjuku-ku Tokyo 163-8019 Japan EMail: hasebe.miki@east.ntt.co.jp Hasebe [Page 74] Internet Draft Examples call flow in race condition Aug 27th,2006 Jun Koshiko NTT-east Corporation 19-2 Nishi-shinjuku 3-chome Shinjuku-ku Tokyo 163-8019 Japan EMail: j.koshiko@east.ntt.co.jp Yasushi Suzuki NTT-east Corporation 19-2 Nishi-shinjuku 3-chome Shinjuku-ku Tokyo 163-8019 Japan EMail: suzuki.yasushi@east.ntt.co.jp Tomoyuki Yoshikawa NTT-east Corporation 19-2 Nishi-shinjuku 3-chome Shinjuku-ku Tokyo 163-8019 Japan EMail: tomoyuki.yoshikawa@east.ntt.co.jp Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity Hasebe [Page 75] Internet Draft Examples call flow in race condition Aug 27th,2006 This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. The Expiration date for this Internet Draft is: Aug 27th, 2006 Hasebe [Page 76]