MSRP The Message Session Relay Protocol

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MSRP - The Message Session Relay Protocol

• speakerwenping zhang
• date2007.11.29

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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.

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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.xxxx1111/2s93i93idjtcp
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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

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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

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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

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Drawback 1/2

• Routing

Proxy server
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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.

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Alice
Bob
INVITE
INVITE sipbob_at_biloxi.example.com SIP/2.0 To
ltsipbob_at_biloxi.example.comgt From
ltsipalice_at_atlanta.example.comgttag786 Call-ID
3413an89KU Content-Type application/sdp cIN
IP4 atlanta.example.com mmessage 7654 TCP/MSRP
aaccept-typestext/plain apathmsrp//atlanta.
example.com7654/jshA7weztastcp
200 OK
SIP/2.0 200 OK To ltsipbob_at_biloxi.example.comgtta
g087js From ltsipalice_at_atlanta.example.comgttag
786 Call-ID 3413an89KU Content-Type
application/sdp cIN IP4 biloxi.example.com mmes
sage 12763 TCP/MSRP aaccept-typestext/plain a
pathmsrp//biloxi.example.com12763/kjhd37s2s20w2
atcp
ACK
MSRP Session
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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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