MSRP - The Message Session Relay Protocol by iee59083

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									MSRP - The Message Session
Relay Protocol

   speaker:wenping zhang
   date:2007.11.29
Outline
   Messaging Schemes
       Page-mode
           SIP + SDP
       Session-mode
           MSRP
   SIP
       Server
       Message syntax
       Method
   SDP
       Structure
   Drawback
   MSRP
       Method
   Future Work
   Reference


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Instant Messaging




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Messaging Schemes 1/2

   Page-mode messaging
        That track only individual messages can be described.
        Uses the SIP Method MESSAGE for transmitting data.




                                                                 4
Messaging Schemes 2/2

   Session-mode messaging
       Messaging that is part of a "session" with a definite start and end.
       The new proposed model by SIMPLE work group using MSRP Protocol.




                                               SEND
                            msrp://jon.xxxx.xxxx.xxxx:1111/2s93i93idj;tcp




                                                                            5
Session Initiation Protocol (SIP)
   A signaling protocol
       The setup, modification, and tear-down of
        multimedia sessions
   SIP + SDP
       Describe the session characteristics
   Separate signaling and media streams




                                                    6
SIP Server

   Proxy servers
       Handle requests or forward requests to other
        servers
       Can be used for call forwarding, time-of-day
        routing, or follow-me services




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SIP Messaging Syntax

   Text-based
       Similar to HTTP
       Disadvantage – more bandwidth consumption
   SIP messages
       Message = start-line
                  *message-header CRLF
                   [message-body]



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SIP for Instant Messaging

   The IETF working group – SIP for Instant
    Messaging and Presence Leveraging
    Extensions (SIMPLE)
   A new SIP method –MESSAGE (RFC 3428)
       This request carries the actual message in a
        message body.
       A MESSAGE request does not establish a SIP
        dialog.



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The Session Description Protocol (SDP)

   The Most Common Message Body
       Be session information describing the media to be
        exchanged between the parties
       SDP, RFC 2327 (initial publication)
   SIP uses SDP in an answer/offer mode
       An agreement between the two parties as to the
        types of media they are willing to share
       RFC 3264 (An Offer/Answer Model with SDP)
           To describe how SDP and SIP should be used together


                                                                  14
The Structure of SDP

   SDP simply provides a format for describing session
    information to potential session participants.
   Text-based Protocol
   The Structure of SDP
       Session Level Info
           Name of the session
           Originator of the session
           Time that the session is to be active
       Media Level Info
           Media type
           Port number
           Transport protocol
           Media format


                                                      15
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Drawback 1/2
   Routing




               Proxy server




                              17
Drawback 2/2
   Overhead




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The Message Session Relay Protocol (MSRP)

   MSRP is a text-based, connection-oriented protocol
    for exchanging arbitrary (binary) MIME content,
    especially instant messages.

   The exchange is carried by some signaling protocol,
    such as the Session Initiation Protocol (SIP). This
    allows a communication user agent to offer a
    messaging session as one of the possible media-
    types in a session.

   SIP can use an offer/answer model to transport the
    MSRP URIs for the media in SDP.

                                                         19
Alice                                                 Bob

                     INVITE
  INVITE sip:bob@biloxi.example.com SIP/2.0
  To: <sip:bob@biloxi.example.com>
  From: <sip:alice@atlanta.example.com>;tag=786
  Call-ID: 3413an89KU200 OK
  Content-Type: application/sdp
  SIP/2.0 200 OK
  To: <sip:bob@biloxi.example.com>;tag=087js
  c=IN IP4 atlanta.example.com
  From: <sip:alice@atlanta.example.com>;tag=786
  m=message 7654 TCP/MSRP *
  Call-ID: 3413an89KU
  a=accept-types:text/plain
                       ACK
  Content-Type: application/sdp
  a=path:msrp://atlanta.example.com:7654/jshA7weztas;tcp
  c=IN IP4 biloxi.example.com
  m=message 12763 TCP/MSRP *
  a=accept-types:text/plain
                 MSRP Session
  a=path:msrp://biloxi.example.com:12763/kjhd37s2s20w2a;tcp



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 MSRP communication primitives 1/2

      SEND Method
           Be used to deliver a
            complete message or a
            chunk (a portion of a
            complete message).




src: www.cs.columbia.edu/~hgs/teaching/ais/slides/sip-suthan.ppt

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MSRP communication primitives 2/2

   REPORT Method
       It report on the status of
        a previously sent
        message, or a range of
        bytes inside a message.




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Future Work

   Joins the MSRP mechanism in existing SIP
    phone (Linux – Linphone).
   How solves MSRP passes through NAT the
    question?




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Reference
   RFC 3261 - SIP: Session Initiation Protocol
     http://www.ietf.org/rfc/rfc3261.txt

   RFC 3428 - Session Initiation Protocol (SIP) Extension for Instant Messaging
     http://www.ietf.org/rfc/rfc3428.txt

   RFC 2327 - SDP: Session Description Protocol
     http://www.ietf.org/rfc/rfc2327.txt

   RFC 3264 - An Offer/Answer Model with the Session Description Protocol (SDP)
     http://www.ietf.org/rfc/rfc3264.txt

   The Message Session Relay Protocol
      draft-ietf-simple-message-sessions




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END




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