Network Working Group T. Froment Internet-Draft C. Lebel Intended status: Standards Track Alcatel-Lucent Expires: August 30, 2007 February 26, 2007 Addressing Record-Route issues in Session Initiation Protocol (SIP) draft-froment-sip-record-route-fix-00 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 August 30, 2007. Copyright Notice Copyright (C) The IETF Trust (2007). Froment & Lebel Expires August 30, 2007 [Page 1]
Internet-Draft SIP Record-Route fix February 2007 Abstract A typical function of a Session Initiation Protocol (SIP) Proxy is to set a Record-Route header on initial requests in order to make subsequent requests pass through it. This header contains a SIP Uniform Resource Identifier (URI) indicating where and how the subsequent requests should be sent to reach the proxy. Like any SIP URI, it can contain sip or sips schemes, IPV4 or IPV6 addresses, and URI parameters that could influence the routing like different transport parameters (UDP, TCP, SCTP...), or a compression indication like "comp=sigcomp". When a proxy has to change some of those parameters between its incoming and outgoing interfaces (multi-homed proxies, transport switching, sip to sips or IPV4 to IPV6 scenarios...), the question arises on what should be put in Record- Route: it is just not possible to make one header having the characteristics of both sides at the same time. This document aims to clarify these scenarios and fix bugs already identified on this topic; it formally suggests the use of the double Record-Route technique as a replacement to the current RFC3261 text, which only describes Record-Route rewriting solution. Froment & Lebel Expires August 30, 2007 [Page 2]
Internet-Draft SIP Record-Route fix February 2007 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 7 3.1. Background: multi-homed proxies . . . . . . . . . . . . . 7 3.2. Problems . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Record-Route rewriting . . . . . . . . . . . . . . . . . . . . 13 5. Double Record-Routing . . . . . . . . . . . . . . . . . . . . 14 6. Conclusion and discussion on normative changes . . . . . . . . 18 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 20 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22 10.1. Normative References . . . . . . . . . . . . . . . . . . . 22 10.2. Informative References . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 24 Intellectual Property and Copyright Statements . . . . . . . . . . 25 Froment & Lebel Expires August 30, 2007 [Page 3]
Internet-Draft SIP Record-Route fix February 2007 1. Introduction Over the years, it has been noticed in multiple interoperability events like SIPIT, that many implementations had interoperability problems due to various Record-Routing issues or misinterpretations of [RFC3261], in particular when a change occurs between the incoming and outgoing sides of a proxy: transport switching, "multi-homed" proxies (including IPV4 to IPV6 interface changes), sip to sips. Multiple documents have addressed the question, each of them generally providing an adequate solution for its specific use case, but none of them gives a general solution or suggests a normative change to actually provide a coherent set of clarifications: - [RFC3486], section 6, describes the double Record-Routing as an alternative to the record-route rewriting in responses. This document is limited in scope to the "comp=sigcomp" parameter when doing compression with SIGCOMP. - [RFC3608], section 6.2, recommends the usage of double Record- Routing instead of the rewriting solution described in [RFC3261] for "Dual-homed" proxies. Those are defined as "proxies connected to two (or more) different networks such that requests are received on one interface and proxied out through another network interface". - ID [draft-ietf-sipping-v6-transition-04], section 3.1.1, mandates double Record-Routing for multi-homed proxies doing IPV4/ IPV6 transitions, when proxy inserts IP addresses. - ID [draft-ietf-sip-sips-01], section 4.2, recommends to apply the double Record-Routing technique when a proxy has to change the scheme from sip to sips; again, the scope is limited to this use case. The observed interoperability problems can be explained by the fact that, despite these multiple documents, RFC3261 description is still not normatively changed, and most implementors don't support extensions like Service-Route ([RFC3608]) or SIGCOMP([RFC3486]). Indeed, why doing so just for implementing a multi-home proxy or transport switching basic function? By the way, this document also aims to clarify identified bugs referenced in [BUG664], [BUG734] and [BUG735]. In particular, it takes into account [BUG664] recommendation, which says that "the language that describes this, needs to clearly capture that this applies to all types of different interface on each side issues, including IPV4 on one side and IPV6 on the other". Froment & Lebel Expires August 30, 2007 [Page 4]
Internet-Draft SIP Record-Route fix February 2007 This document is also following recommendations of [draft-drage-sip-essential-correction-00], which describes the process for handling essential corrections to the Session Initiation Protocol. Froment & Lebel Expires August 30, 2007 [Page 5]
Internet-Draft SIP Record-Route fix February 2007 2. Terminology 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 RFC 2119 [RFC2119]. Froment & Lebel Expires August 30, 2007 [Page 6]
Internet-Draft SIP Record-Route fix February 2007 3. Problem statement 3.1. Background: multi-homed proxies A multi-homed proxy is a proxy connected, like a router, to two or more different networks, with an interface into each network, such that traffic comes "in" one network and goes "out" a different one. A simple model is shown here: +-----+ | U1 | +--+--+ | .2 10.1.1.0/25 | ----------------+---+-... | | .1 +-+-+ | P | +-+-+ | .1 | 192.0.2.1/24 ...---+------+------------------ | | .2 +--+--+ | U2 | +--+--+ U1 has one interface with IP address 10.1.1.2. P has two interfaces and two addresses: -- 10.1.1.1 -- 192.0.2.1 And U2 has one interface and one address, 192.0.2.2. In other words, there is no IP level route between U1 and U2; no ping; no traceroute. They live in entirely different networks. But they can still exchange SIP messages, because P is a SIP Proxy. This works in SIP because P can "record-route". Froment & Lebel Expires August 30, 2007 [Page 7]
Internet-Draft SIP Record-Route fix February 2007 3.2. Problems Handling of Record-Route header in SIP Proxies is specified by following sections of [RFC3261]: On request processing side, [RFC3261], item 4 of section 16.6 states that "The URI placed in the Record-Route header field value MUST be a SIP or SIPS URI. [...] The URI SHOULD NOT contain the transport parameter unless the proxy has knowledge(such as in a private network) that the next downstream element that will be in the path of subsequent requests supports that transport". Following this statement, it is not clear at all that proxy SHOULD put the transport parameter of its outgoing interface in order to rewrite it later in responses: this can not be optional. Then, this section speaks about record-route requirements when transiting from sips to non-sips. It's not clear that the section doesn't apply to TLS to non-TLS transitions where SIPS is not involved (see [BUG734]). On response processing side, [RFC3261] recommends in step 8 of section 16.7 that "If the selected response contains a Record- Route header field value originally provided by this proxy, the proxy MAY choose to rewrite the value before forwarding the response. This allows the proxy to provide different URIs for itself to the next upstream and downstream elements. A proxy may choose to use this mechanism for any reason. For instance, it is useful for multi-homed hosts. If the proxy received the request over TLS, and sent it out over a non-TLS connection, the proxy MUST rewrite the URI in the Record-Route header field to be a SIPS URI". Indeed, [RFC3261] suggests rewriting the record-route header in responses, and mandates it if the request indicated "SIP:". The current text indicates that the record-route value MUST be modified to contain a SIPS URI when routing a response from non-TLS to TLS transports. This makes sense only if the request indicated SIPS. Hop-by-hop TLS needs to be covered separately, see [BUG735]). Let's consider the following scenario: a SIP proxy, doing TCP to UDP transport-switching. Some critical interoperability problems commonly occurs, and it was identified as a frequent problem in SIPIT 18th which took place in April 2006. The statement "The URI SHOULD NOT contain the transport parameter unless the proxy has knowledge(such as in a private network) that the next downstream element that will be in the path of subsequent requests supports that transport", is often considered as confusing: applying this statement, a proxy just put one Record-Route, without any transport parameters, which generally leads to the problem illustrated below: Froment & Lebel Expires August 30, 2007 [Page 8]
Internet-Draft SIP Record-Route fix February 2007 Alice ===== TCP ===== Proxy ===== UDP ===== Bob | | | | F1 INVITE | | |------------------->| F2 INVITE | | |------------------->| | 100 Trying | | |<-------------------| | | | F3 200 OK | | F4 200 OK |<-------------------| |<-------------------| | | | | | F5 ACK | | |--(sent in UDP) X-> | ACK | | |------------------->| | | | | | F6 BYE | | BYE |<-------------------| |<-------------------| | Simplified TCP to UDP proxy scenario description U1 P1 U2 F1 INVITE U1 -> P1 INVITE sip:bob@biloxi.com SIP/2.0 Route: <sip:192.0.2.1;lr;transport=TCP> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:alice@u1.atlanta.com;transport=TCP> F2 INVITE P1 -> U2 INVITE sip:bob@biloxi.com SIP/2.0 Record-Route: <sip:192.0.2.1;lr> (NO transport param) From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:alice@u1.atlanta.com;transport=TCP> Dialog State at U2: Local URI = sip:bob@biloxi.com Remote URI = sip:alice@atlanta.com Remote target = sip:alice@u1.atlanta.com;transport=TCP Route Set = sip:192.0.2.1;lr F3 200 OK U2 -> P1 Froment & Lebel Expires August 30, 2007 [Page 9]
Internet-Draft SIP Record-Route fix February 2007 SIP/2.0 200 OK Record-Route: <sip:192.0.2.1;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:bob@u2.biloxi.com> F4 200 OK P1 -> U1 SIP/2.0 200 OK Record-Route: <sip:192.0.2.1;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:bob@u2.biloxi.com> Dialog State at U1: Local URI = sip:alice@atlanta.com Remote URI = sip:bob@biloxi.com Remote target = sip:bob@u2.biloxi.com Route Set = sip:192.0.2.1;lr F5 ACK U1 -> P1 ACK sip:bob@u2.biloxi.com SIP/2.0 Route: <sip:192.0.2.1;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> F6 BYE U2 -> P1 BYE sip:alice@u1.atlanta.com;transport=TCP SIP/2.0 Route: <sip:192.0.2.1;lr> From: Bob <sip:bob@biloxi.com> To: Alice <sip:alice@atlanta.com> Figure 3: transport switching scenario Since Proxy P1 does not put any transport parameter on Record-Route, subsequent requests of U1, like the ACK sent in F5, will be sent according to the behaviour specified in section 12.2 (requests within a Dialog) of RFC 3261, that means that the Route set is used, and then, applying [RFC3263], the Route "sip:192.0.2.1" will resolve to a UDP transport by default (since no transport parameter is available here), and no NAPTR request will be performed since this is a numeric IP Address. Even if proxy had record-routed its logical name (e.g. p1.example.com), if U1 and U2 use the same DNS server, NAPTR request would resolve to the same transport on both sides. That means, even if we assume that UAs support [RFC3263], if one of the UA sends an Froment & Lebel Expires August 30, 2007 [Page 10]
Internet-Draft SIP Record-Route fix February 2007 initial request using a different transport than the one configured in DNS, this scenario is still problematic. In practice, there are multiple reasons why UAs are rarely using logical names and NAPTR when sending an initial request to a proxy: - Most of UAs have the ability to configure statically their outbound proxy, and it is commonly configured with a numeric IP address. - Most of UAs offer the ability to "force" the transport to be used for initial requests, even if they support [RFC3263]: this is because in some circumstances, people just want to avoid using UDP (trying to avoid congestion, retransmissions or fragmentation), or just because they simply don't support one of the transport! - Some UAs do not support [RFC3263] at all... In previous example, forcing U1 to switch from TCP to UDP between initial request and subsequent request(s) is clearly not the desired default behaviour, and it typically leads to interoperability problems. In any case, if proxy record-route a numeric IP Address and transport switching occurs, something needs to be done. In order to workaround these problems, and to maintain a reasonnable level of interoperability, experience shows that solutions are generally provided on proxy side, the two possible solutions are either: - Record-Route rewriting on responses: Put the transport parameter on the Record-Route of INVITE request sent in F2, so that U2 will correctly send its BYE request in F6 using the same transport as previous messages of the same dialog, and make the Proxy rewrite the Record-Route when processing the 200 OK response, changing "on the fly" the transport parameter to "transport=TCP", so that the Route set will appear to be <sip:192.0.2.1;lr;transport=TCP> for U1 and <sip:192.0.2.1;lr;transport=UDP> for U2. - Double Record-Routing: the proxy puts two Record-Route headers. The first one is set, in this example, to Record-Route: <sip: 192.0.2.1;lr;transport=TCP>, the second one to Record-Route: <sip: 192.0.2.1;lr> with no transport, or with transport=UDP, which means basically the same thing. This is a common practice in implementors community to support double Record-Route AND put the transport parameters. Knowing this problem, some UA implementations sometimes decide to always keep the same transport for a given Dialog, but this choice is Froment & Lebel Expires August 30, 2007 [Page 11]
Internet-Draft SIP Record-Route fix February 2007 erratic, since if the proxy is not Record-Route, the callee may receive the subsequent request through a transport that is not the one put in its Contact. The question of putting or not the transport parameter on Record- Route needs to be clarified. But let appart this question, this problem enlights the utility of rewriting and double Record-Routing techniques which apply for any other multi-homed proxy use case, whenever the proxy changes its IP address or its URI scheme between incoming and outgoing interfaces. This is why, these techniques are described, compared and discussed in the following sections. Froment & Lebel Expires August 30, 2007 [Page 12]
Internet-Draft SIP Record-Route fix February 2007 4. Record-Route rewriting As already outlined in some IETF mailing list discussions: Record- Route rewriting in responses is controversial. Actually, it has often been noticed that letting [RFC3261] with the Record-Route rewriting as the only technique described in core specification is dangerous, due to the fact that rewriting has some heavy drawbacks. Indeed, the consequence of doing rewriting is that the Route seen by the caller is different from the Route seen by the callee, and it has two serious implications: 1) Callee cannot sign the route set, because it gets edited by the proxy in the response. Consequently, end-to-end protection of the route set can not be supported by the protocol. The openness and the end-to-end principles are broken (!)... 2) Proxy must implement special "multi-homed" stateful logic. On the request phase, it goes through output interface calculation and writes the output interface into the route. It must then inspect all responses, grep for an input interface, and selectively edit them to reference the correct output interface: this is a CPU drag. Moreover, it is not clear how a stateless proxy can handle this stateful rewriting operation. That's why, this document would recommend to completely deprecate this technique. However, if it is considered as something that SHOULD NOT be deprecated, it SHOULD be clarified that its scope is wider than just the "sip to sips" use case, and SHOULD be extended to transport switching, or "multi-homed" situations: Thus, on the request processing side: item 4 of section 16.6 of [RFC3261], it SHOULD be noticed that the URI MAY contain the transport parameter or the outgoing interface in case of a multi- homed proxy, and that it would trigger the Record-Route rewriting when processing responses. On the response processing side: step 8 of section 16.7, it SHOULD be noticed that the mechanism applies also to transport switching scenario, and not only to scheme changes. Froment & Lebel Expires August 30, 2007 [Page 13]
Internet-Draft SIP Record-Route fix February 2007 5. Double Record-Routing Critical drawbacks of rewriting technique probably explain why double Record-Routing solution has consequently always been recommended in SIP extensions like [RFC3486] or [RFC3608]. That's also why this document proposes, through an normative change, to introduce it either as an alternative or even as a replacement of rewriting in [RFC3261]. This alternative has many benefits, and is completely backwards compatible with [RFC3261]. It consists in putting as the first value, the Route of receiving interface, including schemes and/or URI parameters, and, as second value, the Route of the sending interface. When processing the response, no modification of the recorded route is required. When double Record-Routing, the proxy will have to handle the second incoming request as a spiral, and consequently devote some space to maintaining a transaction. In order to avoid a spiral, proxy has to be smart and scan an extra route ahead to determine whether the request will spiral through it. If it does, it can optimize the second spiral through itself. Even though this is an implementation decision, it is much more efficient to avoid spiraling, and it means that the appropriate section of[RFC3261] SHOULD be modified: Scanning two routes instead of one implies that proxy behaviour described in section 16.4. "Route Information Preprocessing" of [RFC3261] MAY remove these TWO routes instead of one. This section SHOULD then be modified by adding to the current text "If the first value in the Route header field indicates this proxy, the proxy MUST remove that value from the request" a statement like "If the proxy used double Record-Routing technique for this dialog, as described in [...], the same treatment MAY be applied, and then remove the second value of Route header". This has never been described in existing documents mentioning the double Record-Routing solution. Generally speaking, the time complexity will be less in double Record-Routing since on the response, the proxy does not have to do any re-writes (and thus, no searching). The following example is an extension of example given in[draft-ietf-sipping-v6-transition-04], it illustrates a call flow when doing double Record-Routing with a multi-homed IPV4 to IPV6 proxy, enlightening the Dialog State on each UA. Froment & Lebel Expires August 30, 2007 [Page 14]
Internet-Draft SIP Record-Route fix February 2007 UAC Proxy UAS (IPv4) (IPv4/IPv6) (IPv6) | | | | F1 INVITE | | |------------------->| F2 INVITE | | |------------------->| | 100 Trying | | |<-------------------| | | | F3 200 OK | | F4 200 OK |<-------------------| |<-------------------| | | | | | F5 ACK | | |------------------->| F6 ACK | | |------------------->| | | | | | F7 BYE | | F8 BYE |<-------------------| |<-------------------| | | F9 200 OK | | |------------------->| F10 200 OK | | |------------------->| IPV4 to IPV6 multi-homed proxy illustration U1 P1 U2 F1 INVITE U1 -> P1 INVITE sip:bob@biloxi.com SIP/2.0 Route: <sip:192.0.2.254:5060;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:alice@192.0.2.1> F2 INVITE P1 -> U2 INVITE sip:bob@biloxi.com SIP/2.0 Record-Route: <sip:2001:db8::1;lr> Record-Route: <sip:192.0.2.254:5060;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:alice@192.0.2.1> Dialog State at U2: Local URI = sip:bob@biloxi.com Froment & Lebel Expires August 30, 2007 [Page 15]
Internet-Draft SIP Record-Route fix February 2007 Remote URI = sip:alice@atlanta.com Remote target = sip:alice@192.0.2.1 Route Set = sip:2001:db8::1;lr sip:192.0.2.254:5060:lr F3 200 OK U2 -> P1 SIP/2.0 200 OK Record-Route: <sip:2001:db8::1;lr> Record-Route: <sip:192.0.2.254:5060;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:bob@2001:db8::33> F4 200 OK P1 -> U1 SIP/2.0 200 OK Record-Route: <sip:2001:db8::1;lr> Record-Route: <sip:192.0.2.254:5060;lr> From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> Contact: <sip:bob@2001:db8::33> Dialog State at U1: Local URI = sip:alice@atlanta.com Remote URI = sip:bob@biloxi.com Remote target = sip:bob@2001:db8::33 Route Set = sip:192.0.2.254:5060:lr sip:2001:db8::1;lr F5 ACK U1 -> P1 ACK sip:bob@2001:db8::33 SIP/2.0 Route: sip:192.0.2.254:5060:lr Route: sip:2001:db8::1;lr From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> F6 ACK P1 -> U2 ACK sip:bob@2001:db8::33 SIP/2.0 From: Alice <sip:alice@atlanta.com> To: Bob <sip:bob@biloxi.com> (both routes have been removed by proxy) F7 BYE U2 -> P1 BYE sip:alice@192.0.2.1 SIP/2.0 Froment & Lebel Expires August 30, 2007 [Page 16]
Internet-Draft SIP Record-Route fix February 2007 Route: sip:2001:db8::1;lr Route: sip:192.0.2.254:5060:lr From: Bob <sip:bob@biloxi.com> To: Alice <sip:alice@atlanta.com> F8 BYE P1 -> U1 BYE sip:alice@192.0.2.1 SIP/2.0 From: Bob <sip:bob@biloxi.com> To: Alice <sip:alice@atlanta.com> F9 SIP/2.0 200 OK U1 -> P1 From: Bob <sip:bob@biloxi.com> To: Alice <sip:alice@atlanta.com> F10 SIP/2.0 200 OK P1 -> U2 From: Bob <sip:bob@biloxi.com> To: Alice <sip:alice@atlanta.com> Figure 5: Multi-homed IPV4 to IPV6 double Record-Routing illustration Froment & Lebel Expires August 30, 2007 [Page 17]
Internet-Draft SIP Record-Route fix February 2007 6. Conclusion and discussion on normative changes As a consequence of this document, [RFC3261] SHOULD be modified to either: - Deprecate rewriting. - Introduce double Record-Routing as an alternative to rewriting. In this case, given the strong drawbacks of rewriting (but willing to keep the backward compatibility of implementation already supporting it), it could be reasonable to let rewriting as a solution that MAY be used, and make double record-routing as the solution that SHOULD be used. Sections 16.4, of [RFC3261] on "Route Information Preprocessing" SHOULD then be reworded as recommended in section 5 of this document. In any case, the clarification on multi-homed and transport switching scenarios when processing requests and responses is needed: this is important in order to avoid the interoperability problems that have been identified. It would necessitate to reword sections 16.6, item 4 and 16.7, step 8 of [RFC3261]. Froment & Lebel Expires August 30, 2007 [Page 18]
Internet-Draft SIP Record-Route fix February 2007 7. IANA Considerations This document does not require any actions by IANA. Froment & Lebel Expires August 30, 2007 [Page 19]
Internet-Draft SIP Record-Route fix February 2007 8. Security Considerations The double Record-Routing technique reveals some level of network topology and proxy server capabilities: IPv4 and IPv6 support, SCTP support, sigcomp support, etc. to a malicious attacker. This is a bit more than the normal IP address, naming scheme information that is usually part and parcel of every SIP request sent out in the clear. It MAY have an impact on services involving topology hidding or privacy, as specified in [RFC3323]. Froment & Lebel Expires August 30, 2007 [Page 20]
Internet-Draft SIP Record-Route fix February 2007 9. Acknowledgments Vijay K. Gurbani who provided important references and substantial modifications, also raising security considerations. Dean Willis who contributed, through the mailing lists, to most of the problem statement elements. Tom Batsele who helped to clarify the transport-switching issues. Froment & Lebel Expires August 30, 2007 [Page 21]
Internet-Draft SIP Record-Route fix February 2007 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. 10.2. Informative References [BUG664] Sparks, RS., "Bug 664: Double record routing", October 2002. [BUG734] Sparks, RS., "Bug 734: Record-route manipulation rules for requests wrt SIPS vs single-hop TLS are unclear", September 2003. [BUG735] Sparks, RS., "Bug 735: Record-route manipulation rules for responses wrt SIPS vs hop-hop TLS are incorrect", September 2003. [RFC3261] Schulzrinne, HS., Camarillo, GC., Johnston, AJ., Rosenberg, JR., Peterson, JP., Sparks, RS., Handley, MH., and ES. Schooler, "SIP: Session Initiation Protocol", June 2002. [RFC3263] Schulzrinne, HS. and JR. Rosenberg, "Session Initiation Protocol (SIP): Locating SIP Servers", June 2002. [RFC3323] Peterson, JP., "A Privacy Mechanism for the Session Initiation Protocol (SIP)", October 2003. [RFC3486] Camarillo, GC., "Compressing the Session Initiation Protocol (SIP)", February 2003. [RFC3608] Willis, DW. and BH. Hoeneisen, "Session Initiation Protocol (SIP) Extension Header Field for Service Route Discovery During Registration", October 2003. [draft-drage-sip-essential-correction-00] Drage, KD., "A Process for Handling Essential Corrections to the Session Initiation Protocol (SIP)", October 2003. [draft-ietf-sip-sips-01] Audet, FA., "Guidelines for the use of the SIPS URI Scheme in the Session Initiation Protocol (SIP)", February 2007. [draft-ietf-sipping-v6-transition-04] Gurbani, VG., Camarillo, GC., and KEM. Malki, "IPv6 Froment & Lebel Expires August 30, 2007 [Page 22]
Internet-Draft SIP Record-Route fix February 2007 Transition in the Session Initiation Protocol (SIP)", September 2006. Froment & Lebel Expires August 30, 2007 [Page 23]
Internet-Draft SIP Record-Route fix February 2007 Authors' Addresses Thomas Froment Alcatel-Lucent 1 rue Ampere - BP 80056 Massy, Paris 91302 France Email: Thomas.Froment@alcatel-lucent.fr Christophe Lebel Alcatel-Lucent Lieu dit Le Mail Orvault, 44708 France Email: Christophe.Lebel@alcatel-lucent.fr Froment & Lebel Expires August 30, 2007 [Page 24]
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