Improving the Routing Efficiency of SIP Instant MessageSIP 即時傳訊之繞送效能研究

adviser ： Quincy Wu

speaker ： Wenping Zhang

date ： 2008.03.13

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Outline

Introduction 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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Introduction 1/2

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Introduction 2/2

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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.

User 1 User 2

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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.

MSRP

Proxy

User 1 User 2

SIP SIP

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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 serv

ers Can be used for call forwarding, time-of-day routin

g, or follow-me services

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UA 1<sip:UA1@pc1.home.net>

UA 2<sip:UA2@station1.work.com>

Proxy Serversip:server.work.com

(1) INVITEUA2@server.work.com (2) INVITE

UA2@station1.work.com

(3) 100 Trying(4) 180 Ringing

(5) 180 Ringing

(6) 200 OK(7) 200 OK

(8) ACKUA2@station1.work.com (9) ACK

UA2@station1.work.com

Connection (Media Stream)

(10) BYEUA2@station1.work.com (11) BYE

UA2@station1.work.com

(12) 200 OK(13) 200 OK

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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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UA 1 UA 2Proxy Server

(1) MESSAGE(2) MESSAGE

(3) 200 OK(4) 200 OK

(5) MESSAGE(6) MESSAGE

(7) 200 OK(8) 200 OK

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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

Proxy server

Bob

Mary

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Drawback 2/2

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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

INVITEINVITE sip:bob@biloxi.example.com SIP/2.0To: <sip:bob@biloxi.example.com>From: <sip:alice@atlanta.example.com>;tag=786Call-ID: 3413an89KUContent-Type: application/sdp

c=IN IP4 atlanta.example.comm=message 7654 TCP/MSRP *a=accept-types:text/plaina=path:msrp://atlanta.example.com:7654/jshA7weztas;tcp

200 OKSIP/2.0 200 OKTo: <sip:bob@biloxi.example.com>;tag=087jsFrom: <sip:alice@atlanta.example.com>;tag=786Call-ID: 3413an89KUContent-Type: application/sdp

c=IN IP4 biloxi.example.comm=message 12763 TCP/MSRP *a=accept-types:text/plaina=path:msrp://biloxi.example.com:12763/kjhd37s2s20w2a;tcp

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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UA 1 UA 2Proxy Server

(SIP) INVITE(SIP) INVITE

(SIP) 200 OK(SIP) 200 OK

(SIP) ACK(SIP) ACK

(MSRP) SEND(MSRP) 200 OK

(MSRP) SEND(MSRP) 200 OK

(SIP) BYE(SIP) BYE

(SIP) 200 OK(SIP) 200 OK

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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 http://www.ietf.org/rfc/rfc4975.txt