The Message Session Relay Protocol (MSRP)
RFC 4975

Network Working Group                                   B. Campbell, Ed.
Request for Comments: 4975                              Estacado Systems
Category: Standards Track                                   R. Mahy, Ed.
                                                             Plantronics
                                                        C. Jennings, Ed.
                                                     Cisco Systems, Inc.
                                                          September 2007

               The Message Session Relay Protocol (MSRP)

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document describes the Message Session Relay Protocol, a
   protocol for transmitting a series of related instant messages in the
   context of a session.  Message sessions are treated like any other
   media stream when set up via a rendezvous or session creation
   protocol such as the Session Initiation Protocol.

Campbell, et al.            Standards Track                     [Page 1]
RFC 4975                          MSRP                    September 2007

Table of Contents

   1. Introduction ....................................................4
   2. Conventions .....................................................5
   3. Applicability of MSRP ...........................................5
   4. Protocol Overview ...............................................6
   5. Key Concepts ....................................................9
      5.1. MSRP Framing and Message Chunking ..........................9
      5.2. MSRP Addressing ...........................................10
      5.3. MSRP Transaction and Report Model .........................11
      5.4. MSRP Connection Model .....................................12
   6. MSRP URIs ......................................................14
      6.1. MSRP URI Comparison .......................................15
      6.2. Resolving MSRP Host Device ................................16
   7. Method-Specific Behavior .......................................17
      7.1. Constructing Requests .....................................17
           7.1.1. Sending SEND Requests ..............................18
           7.1.2. Sending REPORT Requests ............................21
           7.1.3. Generating Success Reports .........................22
           7.1.4. Generating Failure Reports .........................23
      7.2. Constructing Responses ....................................24
      7.3. Receiving Requests ........................................25
           7.3.1. Receiving SEND Requests ............................25
           7.3.2. Receiving REPORT Requests ..........................27
   8. Using MSRP with SIP and SDP ....................................27
      8.1. SDP Connection and Media-Lines ............................28
      8.2. URI Negotiations ..........................................29
      8.3. Path Attributes with Multiple URIs ........................30
      8.4. Updated SDP Offers ........................................31
      8.5. Connection Negotiation ....................................31
      8.6. Content Type Negotiation ..................................32
      8.7. Example SDP Exchange ......................................34
      8.8. MSRP User Experience with SIP .............................35
      8.9. SDP Direction Attribute and MSRP ..........................35
   9. Formal Syntax ..................................................36
   10. Response Code Descriptions ....................................38
      10.1. 200 ......................................................38
      10.2. 400 ......................................................38
      10.3. 403 ......................................................38
      10.4. 408 ......................................................39
      10.5. 413 ......................................................39
      10.6. 415 ......................................................39
      10.7. 423 ......................................................39
      10.8. 481 ......................................................39
      10.9. 501 ......................................................39
      10.10. 506 .....................................................40

Campbell, et al.            Standards Track                     [Page 2]
RFC 4975                          MSRP                    September 2007