Network Working Group P. Kim Internet-Draft Korea Polytechnic University Expires: December 31, 2005 June 29, 2005 A New Mechanism for SIP over Mobile IPv6 draft-pskim-sip-mipv6-00.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. This Internet-Draft will expire on December 31, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This draft proposes a new mechanism for Session Initiation Protocol (SIP) over Mobile IPv6. In this mechanism, a home agent (HA) on home subnet acts as a redirect server and a registrar for SIP as well as a home router for Mobile IPv6. Thus, a binding cache in the HA contains location information for SIP as well as home registration entries for Mobile IPv6. An access router on foreign subnet acts as only a router that offers a domain name. To implement the proposed mechanism, some messages used in network layer are newly defined, such as a router advertisement, a router solicitation and a binding update. In the proposed mechanism, a mobile node doesn't require dynamic host configuration protocol (DHCP) and thus both home and foreign subnets don't need DHCP servers, unlike existing mechanisms on Mobile IPv4. Kim A New Mechanism for SIP over Mobile IPv6 [Page 1] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Network Architecture for Proposed Mechanism . . . . . . . . . 3 4. New Messages for Proposed Mechanism. . . . . . . . . . . . . . 4 4.1 New Router Advertisement Message . . . . . . . . . . . . . . 4 4.2 New Router Advertisement Message . . . . . . . . . . . . . . 5 4.3 New Binding Update Message . . . . . . . . . . . . . . . . . 5 5. Basic Operation Procedure of Proposed Mechanism . . . . . . . 6 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 8 Intellectual Property and Copyright Statements . . . . . . . . 9 1. Introduction Over the past few years, an important trend is the emergence of voice over IP (VoIP) services and its rapid growth. For VoIP services, the Session Initiation Protocol (SIP) has been standardized by IETF [RFC3261]. SIP is an application layer protocol used for establishing and tearing down multimedia sessions.Meanwhile, mobility support is also becoming important because of the recent blossoming of mobile appliances, such as mobile phone, handheld PC, laptop computer, and the high desire to have seamless network connectivity. To support mobility for IPv4, Mobile IPv4 [RFC2002] was designed by IETF. In addition, in recent, to solve the address exhaustion problem and the routing optimization problem with Mobile IPv4, Mobile IPv6 has been standardized by IETF [RFC3775] for IPv6 [RFC2461]. Even though the original SIP and its applications did not consider the mobility of the end nodes, there have been ongoing research efforts to support mobility in the current SIP [Moh1999], [Seol2002], [Kwon2002]. These works have been researched on Mobile IPv4 because Mobile IPv6 was not well established until recent. To authors' knowledge, there seems to be no well established result for SIP over Mobile IPv6. However, as mentioned before, there are the address exhaustion problem and the routing optimization problem in Mobile IPv4. Therefore, mechanisms for SIP over Mobile IPv6 might be required for wireless and mobile communication environments. In this draft, a new mechanism for SIP over Mobile IPv6 is proposed. In this mechanism, a home agent (HA) on home subnet acts as a redirect server and a registrar for SIP as well as a home router for Mobile IPv6. That is, the HA provides its inherent functions of Mobile IPv6, such as a router advertisement and a home registration for a mobile node (MN). In addition, for SIP, the HA accepts a location registration request of the MN, places the information it receives in this request into a location database, and returns the location information of the MN to a correspondent node (CN). Thus, a binding cache in the HA contains location information for SIP as well as home registration entries for Mobile IPv6. On the other side, an access router on foreign subnet, which will be called a foreign router (FR) hereafter, provides only a router advertisement for the MN. Kim A New Mechanism for SIP over Mobile IPv6 [Page 2] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 To implement the proposed mechanism, in this draft, some new messages used in network layer are defined by adding some fields to existing messages in [RFC3775]. Firstly, in order that HA and FR offer a subnet prefix and a domain name for the MN, a router advertisement (RA) message is newly defined. Using this RA message, the MN can make a new Uniform Resource Identifier (URI) as well as a home address (HoA) or a care-of address (CoA). Secondly, in order that the MN solicits the HA or FR for the RA with a domain name as well as a subnet prefix, a router solicitation (RS) message is newly defined. Lastly, when the MN changes its subnet and thus makes the CoA and the new URI, to do simultaneously both location registration for SIP and home registration for Mobile IPv6 with the HA, a binding update (BU) message is newly defined. In the proposed mechanism, the MN doesn't require dynamic host configuration protocol (DHCP) [RFC1541] and thus both home and foreign subnets don't need DHCP servers. On the other hand, existing mechanisms on Mobile IPv4 required DHCP for the MN, and used DHCP servers for the MN to get the HoA or CoA and the new URI, as shown in existing works. In addition, the proposed mechanism provides the efficient optimized routing where speech packets sent by the CN are routed directly to the MN, whereas existing mechanisms could not due to the triangle routing. 2. Requirements 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 [RFC2119]. 3. Network Architecture for Proposed Mechanism In this draft, a new mechanism for SIP over Mobile IPv6 is proposed for a wireless mobile network. The network considered for the proposed mechanism consists of a mobile node (MN), a correspondent node (CN), a home agent (HA), and a foreign router (FR). The MN acts as a user agent (UA) for SIP as well as a mobile host for Mobile IPv6. That is, in addition to its inherent functions for Mobile IPv6, the MN creates a new SIP request and generates a response to a SIP request. The CN also acts as a user agent (UA) for SIP as well as a peer node with which a mobile node is communicating for Mobile IPv6. The HA on home subnet acts as a redirect server and a registrar for SIP as well as a home router for Mobile IPv6. That is, the HA provides its inherent functions of Mobile IPv6, such as a router advertisement and a home registration for a mobile node (MN). In addition, for SIP, the HA accepts a location registration request of the MN, places the information it receives in this request into a location database, and returns the location information of the MN to the CN. Thus, the binding cache in the HA contains location Kim A New Mechanism for SIP over Mobile IPv6 [Page 3] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 information for SIP as well as home registration entries for Mobile IPv6. On the other side, the FR provides only a router advertisement for the MN. 4. New Messages for Proposed Mechanism In this section, to implement the proposed mechanism, some messages used in network layer are newly defined by adding some fields to existing messages in [RFC3775], such as a router advertisement, a router solicitation and a binding update. 4.1 New Router Advertisement Message In order that HA and FR offer a subnet prefix and a domain name for the MN, a router advertisement (RA) message is newly defined by adding some fields to existing message in [RFC3775]. Using this RA message, the MN can make a new Uniform Resource Identifier (URI) as well as a home address (HoA) or a care-of address (CoA). 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Cur Hop Limit |M|O|H|D|Reserv | Router Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reachable Time | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Retrans Timer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Domain Information + | (ex: kpu.ac.kr or ssslab.kpu.ac.kr) | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fig.1 New Router Advertisement Message o Domain Name Flag (D) : This bit is set in a RA to indicate that the router sending this RA also include a domain name of current subnet. o Reserved : Reduced from a 5-bit field to a 4-bit field to account for the addition of the above bit. o Domain Name : The domain name of current subnet where the MN is attached. The data in the domain name should be encoded according to DNS encoding rules. For example, kpu.ac.kr or ssslab.kpu.ac.kr. Kim A New Mechanism for SIP over Mobile IPv6 [Page 4] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 o Subtype: Subtype field defines the link type of the mobile node included in the Link Characteristic Information field. o Other fields : See [RFC3775] The source address field in the IP header carrying this message is the link-local address assigned to the interface from which this message is sent. The destination address field in the IP header carrying this message is typically the source address of an invoking router solicitation or the all-nodes multicast address. 4.2 New Router Solicitation Message In order that the MN solicits the HA or FR for a router advertisement with a domain name as well as a subnet prefix, a router solicitation (RS) message is newly defined by adding some fields to existing message in [RFC3775]. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |D| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fig.2 New Router Solicitation Message o Domain Name Request Flag (D) : This bit is set in a RS to indicate that the MN requests a domain name of current subnet. o Reserved : Reduced from a 32-bit field to a 31-bit field to account for the addition of the above bit. o Other fields : See [RFC3775] The source address field in the IP header carrying this message is the IP address of MN. The destination address field in the IP header carrying this message is typically the all-routers multicast address. 4.3 New Binding Update Message When the MN changes its subnet and thus makes the CoA and the new URI, to do simultaneously both location registration for SIP and home registration for Mobile IPv6 with the HA, a new binding update (BU) message is newly defined by adding some fields to existing message in [RFC3775]. Kim A New Mechanism for SIP over Mobile IPv6 [Page 5] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence # | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |A|H|L|K| Reserved | Lifetime | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Header Ext Len | Option Type | Option Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + HoA + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + New URI + | (ex: pskim@kpu.ac.kr or pskim@ssslab.kpu.ac.kr) | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Fig.3 New Binding Update Message o Option Type : 10 (or any available value) o New URI : The new URI of the MN. For example, pskim@kpu.ac.kr or pskim@ssslab.kpu.ac.kr o Other fields : See [RFC3775] The source address field in the IP header carrying this message is the CoA of the MN. The destination address field in the IP header carrying this message is the IP address of the HA. This BU message contains the Home Address destination option that has the HoA of the MN. 5. Basic Operation Procedure of Proposed Mechanism In this section, the basic operation of the proposed mechanism is explained in detail. The MN is assumed to be the callee and the CN is assumed to be the caller. It is also assumed that the MN's HoA is 3ffe:2e01:2a:100::10 and URI is pskim@kpu.ac.kr in a home subnet. The CN's URI is assumed to be peter@mipv6.com. When the MN changes its subnet and thus attaches to a foreign subnet, it will receive solicited RA or unsolicited RA from the FR. To receive the solicited RA, the MN sends the RS with setting Domain Kim A New Mechanism for SIP over Mobile IPv6 [Page 6] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 Name Request Flag (D) to the FR as shown in Fig. 2. Note that this RS would be optional. The RA in Fig. 1 contains the subnet prefix for the MN's CoA configuration and the domain name for the MN's new URI configuration. In foreign subnet, the address prefix is 3ffe:2e01:2a:200::/64 and the domain name is ssslab.kpu.ac.kr. Then, the MN makes the CoA as 3ffe:2e01:2a:200::10 and the new URI as pskim@ssslab.kpu.ac.kr. To do simultaneously both location registration for SIP and home registration for Mobile IPv6 with the HA, the MN sends the BU with both CoA and new URI to the HA, using the newly defined message in Fig. 3. If the HA accepts the BU, it update its binding cache entry for the MN. If the URI is not changed, the only CoA is updated in the binding cache. This binding cache is an effective database containing mappings among the original URI, the current URI, the HoA and the CoA. The CN with peter@mipv6.com wants to invite the MN with pskim@kpu.ac.kr The CN translates the domain name kpu.ac.kr to a numeric IP address, by a DNS lookup, where the HA may be found. An INVITE request is generated and sent to this HA. Note that the HA does not issue any SIP requests of its own. After receiving a request other than CANCEL, the HA either refuses the request or gathers the MN's current location information from the binding cache and returns a final response of class 3xx. For well-formed CANCEL requests, it returns a 2xx response. Then, when the HA accepts the invitation, it gathers the MN's current location information, such as the HoA 3ffe:2e01:2a:100::10, the CoA 3ffe:2e01:2a:200::10 and the new URI pskim@ssslab.kpu.ac.kr, from the binding cache. Thus, the HA returns a 302 response (Moved Temporarily) with MN's current location information. The CN acknowledges the response with an ACK request to the HA. Then, the CN issues a new INVITE request based on the MN's current URI pskim@ssslab.kpu.ac.kr. This request is sent to the MN's CoA 3ffe:2e01:2a:200::10. In this case, the call succeeds and a response indicating this is sent to the CN. The signaling is completed with an ACK from the CN to the MN. After this call setup, the real speech communication is going on. In the proposed mechanism, the MN doesn' require dynamic host configuration protocol (DHCP) and thus both home and foreign subnets don't need DHCP servers. On the other hand, existing mechanisms on Mobile IPv4 required DHCP for the MN, and used DHCP servers for the MN to get the HoA or CoA and the new URI, as shown in existing mechanisms. In addition, the proposed mechanism uses the optimized routing between the MN and the CN. That is, speech packets sent by the caller are routed directly to the callee. On the other hand, in existing mechanisms, speech packets that are sent by the caller to the callee connected to a foreign subnet are routed first to the callee's HA and then tunneled to the callee's CoA. Therefore, the proposed mechanism might be more efficient in terms of speech delay and resource consumption than existing mechanisms, because, in general, the speech packets will have to traverse fewer subnets on their way to their destination. Kim A New Mechanism for SIP over Mobile IPv6 [Page 7] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 6. References [RFC3261] Rosenberg, J. et al, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [RFC2002] Perkins, C., "IP Mobility Support", RFC 2002, October 1996 [RFC3775] Johnson, D. B., "Mobility Support in IPv6", RFC 3775, June 2004 [RFC1541] Droms, R., "Dynamic Host Configuration Protocol", RFC 1541, October 1993 [Moh1999] Moh, M. et al, "Mobile IP telephony: mobility support of SIP", Proc. Int. Conf. on Computer Communications and Networks, pp. 554-559, 1999 [Seol2002] Seol, S. et al, "Experiments and analysis of voice over Mobile IP", Proc. IEEE Int. Symposium on Personal, Indoor and Mobile Radio Communications, pp. 997-981, 2002 [Kwon2002] Kwon, T. et al, "Mobility management for VoIP service: Mobile IP vs. SIP", IEEE Wireless Communications, Vol.9, No. 5, pp 66-75, 2002 Authors' Addresses Pyung-Soo Kim Department of Electronics Engineering, Korea Polytechnic University, 2121 Jungwang-Dong, Shiheung City, Gyeonggi-Do 429-793 KOREA Phone: +82 31 496 8413 EMail: pskim@kpu.ac.kr Kim A New Mechanism for SIP over Mobile IPv6 [Page 8] Internet-Draft A New Mechanism for SIP over Mobile IPv6 July 2005 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 implementers 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 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 (2005). 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. Kim A New Mechanism for SIP over Mobile IPv6 [Page 9]