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Blau 5 (if approved) Ericsson AB 6 Expires: May 22, 2010 November 18, 2009 8 Sesstion Matching Update for the Message Session Relay Protocol (MSRP) 9 draft-holmberg-simple-msrp-sessmatch-00.txt 11 Abstract 13 This document updates the session matching procedure defined in 14 section 7.3 of RFC 4975, so that an MSRP UA only uses the session-id 15 part of the MSRP URI in order to perform the consistency checks. The 16 update allows intermediate network entities (ALGs) to modify the 17 address information in the MSRP URI of the SDP a=path attribute, 18 without the need for the intermediate to terminate and do the 19 correlating modifications in the associated MSRP messages. 21 Status of this Memo 23 This Internet-Draft is submitted to IETF in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF), its areas, and its working groups. Note that 28 other groups may also distribute working documents as Internet- 29 Drafts. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 The list of current Internet-Drafts can be accessed at 37 http://www.ietf.org/ietf/1id-abstracts.txt. 39 The list of Internet-Draft Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 This Internet-Draft will expire on May 22, 2010. 44 Copyright Notice 46 Copyright (c) 2009 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3. Applicability statement . . . . . . . . . . . . . . . . . . . . 3 64 4. Normative update of RFC 4975 . . . . . . . . . . . . . . . . . 3 65 4.1. General . . . . . . . . . . . . . . . . . . . . . . . . . . 4 66 4.2. RFC4975: 7.3 Receiving Requests . . . . . . . . . . . . . . 4 67 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 68 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 69 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5 70 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 71 8.1. Normative References . . . . . . . . . . . . . . . . . . . 5 72 8.2. Informative References . . . . . . . . . . . . . . . . . . 5 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 5 75 1. Introduction 77 MSRP [RFC4975] is designed to use MSRP relays [RFC4976] as a means 78 for NAT traversal and policy enforcement. 80 Many networks in which MSRP usage is emerging also contain generic 81 ALGs, which might control media relays and perform tasks such as 82 performance monitoring, lawful intercept, address domain bridging, 83 interconnect SLA policy enforcement, etc. An example here is the 84 Interconnect Border Control Function (IBCF) [3GPP TS23.228] defined 85 by 3GPP, which controls a media relay that handles all types of SIP 86 session media (voice, video, MSRP, etc). 88 Due to the fact that MSRP UAs check consistence between address 89 information in the MSRP messages and in the SDP a=path attribute, 90 this forces the IBCF/media relay to act as an SDP aware MSRP B2BUA, 91 whereas for basically all other UDP and TCP transported based media 92 sessions it can acts as an SDP aware Relay- NAPT - which is much 93 simpler than having to act as an MSRP B2BUA. 95 In order to use general NAT traversal methods, an ALGs, this document 96 updates the session matching procedures defined in section 7.3 of 97 [RFC4975], so that MSRP endpoints only use the session-id part when 98 they compare the MSRP URI in the SDP a=path attribute with the 99 corresponding MSRP URI in MSRP messages. 101 2. Conventions 103 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 104 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 105 document are to be interpreted as described in BCP 14, RFC 2119 106 [RFC2119]. 108 3. Applicability statement 110 This document updates section 7.3 (Receiving Requests) of [RFC4975]. 111 An MSRP UA MUST implement the procedures defined in this document in 112 order to interwork with remote MSRP UAs in a network where 113 intermediate network entities might modify the address information in 114 the MSRP URI of the SDP a=path attribute. 116 4. Normative update of RFC 4975 117 4.1. General 119 This section defines the updated text for section 7.3 (Receiving 120 Requests) of [RFC4975]. 122 4.2. RFC4975: 7.3 Receiving Requests 124 The receiving endpoint MUST first check the URI in the To-Path to 125 make sure the request belongs to an existing session. When the 126 request is received, the To-Path will have exactly one URI, of which 127 the session-id component MUST map to an existing session that is 128 associated with the connection on which the request arrived. If this 129 is not true, then the receiver MUST generate a 481 error and ignore 130 the request. Note that if the Failure-Report header field had a 131 value of "no", then no error report would be sent. 133 5. Security Considerations 135 Due to the change of the session matching procedure, MSRP endpoints 136 can only check that the session-id part of the MSRP URI carried in 137 the MSRP messages matches the session-id which was provided in the 138 associated SDP a=path attribute. Differing from [RFC4975], the host/ 139 domain part of the MSRP URI is thus not checked. However, since a 140 man-in-the-middle would in any case be able to modify the domain 141 information in both the SDP and the MSRP messages, this does not 142 introduce any new security risk. 144 Even if MSRP entities do not use the MSRP URI domain part to perform 145 session matching, if the domain information is different in the SDP 146 a=path attribute and the associated MSRP messages the MSRP entities 147 might be able to determine whether one or more intermediates have 148 been inserted in the message path. With the current session matching 149 procedures, intermediates would have to modify both the domain part 150 of the MSRP URI both in the SDP a=path attribute and the associated 151 MSRP messages, which means that MSRP entities cannot compare the 152 domain information in order to determine whether intermediates have 153 been inserted in the message path. 155 When intermediates are used, MSRP endpoints which uses security 156 mechanisms might not be able to determine whether security is 157 provided end-to-end. However, that issue is generic to all types of 158 media. 160 6. IANA Considerations 162 This document updates section 7.3 of [RFC4975] 164 7. Acknowledgements 166 Thanks to Ben Campbell, Remi Denis-Courmont, Nancy Greene, Hadriel 167 Kaplan, Adam Roach and Robert Sparks for their guidance and input in 168 order to produce this document. 170 8. References 172 8.1. Normative References 174 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 175 Requirement Levels", BCP 14, RFC 2119, March 1997. 177 [RFC2606] Eastlake, D. and A. Panitz, "Reserved Top Level DNS 178 Names", BCP 32, RFC 2606, June 1999. 180 [RFC3323] Peterson, J., "A Privacy Mechanism for the Session 181 Initiation Protocol (SIP)", RFC 3323, November 2002. 183 [RFC4572] Lennox, J., "Connection-Oriented Media Transport over the 184 Transport Layer Security (TLS) Protocol in the Session 185 Description Protocol (SDP)", RFC 4572, July 2006. 187 [RFC4975] Campbell, B., Mahy, R., and C. Jennings, "The Message 188 Session Relay Protocol (MSRP)", RFC 4975, September 2007. 190 [RFC4976] Jennings, C., Mahy, R., and A. Roach, "Relay Extensions 191 for the Message Sessions Relay Protocol (MSRP)", RFC 4976, 192 September 2007. 194 8.2. Informative References 196 Authors' Addresses 198 Christer Holmberg 199 Ericsson 200 Hirsalantie 11 201 Jorvas 02420 202 Finland 204 Email: christer.holmberg@ericsson.com 205 Staffan Blau 206 Ericsson AB 207 P.O Box 407 208 Sweden 210 Email: staffan.blau@ericsson.com