SIP, Presence and Instant Messaging. Spring PIM 2001 SIP, Presence and IM Session Initiation...

SIP, Presence and Instant Messaging

www.dynamicsoft.comSpring PIM 2001

SIP, Presence and IM

Session Initiation Protocol (SIP)

Developed in mmusic Group in IETF Proposed standard RFC2543, February 1999 Work began 1995 Part of Internet Multimedia Conferencing Suite

Main Functions Invite users to sessions

Find the user’s current location, match with their capabilities and preferencesin order to deliver invitation

Carry opaque session descriptions

Modification of sessions Termination of sessions



Protocol Components User Agent Client (UAC)

End systems Send SIP requests

User Agent Server (UAS) Listens for call requests Prompts user or executes program to

determine response

User Agent UAC + UAS

Redirect Server “Network” server; redirects users to try other

server

Proxy Server “Network Server” Proxies request to another

server Can “fork” request to multiple servers, creating a search tree

Registrar receives registrations regarding current user

locations



SIP Architecture

Request

Response

Media

1

2

3

45

67

8

9

1011

12

SIP Client

SIP Redirect Server

SIP ProxySIP Proxy

SIP Client(User Agent Server)

Location Service

13

14



SIP Message Syntax Many header fields from

http

Payload contains a media description

SDP - SessionDescription Protocol

INVITE sip:[email protected] SIP/2.0From: J. Rosenberg <sip:[email protected]>Subject: That pay increaseTo: Eric Sumner <sip:[email protected]>Via: SIP/2.0/UDP pc13.dynamicsoft.comCall-ID: [email protected]: application/sdpCSeq: 4711 INVITEContent-Length: 187

v=0o=jdrosen 53655765 2353687637 IN IP4 122.3.44.12s= [email protected]=IN IP4 122.3.44.12t=0 0m=audio 3456 RTP/AVP 0



SIP Benefits Integration with IP Applications

MIME URIs DNS

Scalability Stateless operation SRV usage Multi-hop networks

Session Independence Usable for interactive games,

chat, voice, video

Recoverability State stored in messages Re-opening of TCP connections

Extension Management Adding headers Adding methods Adding bodies Require and Proxy-Require

Interoperability New Services!

Integration with IM, presence, email, web



What Does Presence Have to Do With SIP? How to Deliver Presence

Need a network that can identify users independent of location

Need a way to forward subscription requests to server handling that user

Need a way for user to tell server its location and other presence data

Need a network which can forward notifications to subscribers

Needs to scale Needs to deliver messages in

real time

What Does a SIP Network Do? Identifies users independent of

location Forwards requests (INVITE or

otherwise) to server handling user REGISTER allows network to tell

server its location and other information [later]

Can forward messages back to originators in reverse direction

Scales Delivers messages in real time

(call setup delays)



SIP Already Provides Publication Capability REGISTER is a Publication Message

for Locations

Allows for SIP and Other URL Types

Multiple Entities Can Publish for the Same Address

SIP Caller Preferences Extension Allows for Attributes for Locations Mobile, landline Home, business Preferences Audio, video - MIME capability

Registrar

Registrar



SIP Extension for Presence

New Entity: Presence Agent Purely logical entity Knows presence state of user Receives SUBSCRIBE requests Generates NOTIFY requests Co-located with proxy/registrar or User Agent

Basic Operation Subscriber send SUBSCRIBE Routed to PA using normal SIP PA authorizes subscriber Acceptance contains presence state NOTIFY sent when state changes

Routed using SIP Record-Route

REGISTER

SUBSCRIBE

NOTIFY

Presence Agent +Proxy/Registrar = Presence Server

Proxy

Subscriber

Presentity



Features of SIP For Presence Extension End Users Can Perform Notifications

Scalability

Presence Agent Function Can Migrate Network provides service when user is offline When user is online, subscriptions migrate to user

Authorization is orthogonal

Multiple Entities Can Generate Presence Information for One Presentity Mobile phone, PDA, laptop and desktop PC

Traditional SIP Proxies Route SUBSCRIBE and NOTIFY

Presence Data is Orthogonal



SIP Extension for Instant Messaging Operation of Extension

Messages carried in SIP messages New method - MESSAGE Routed to recipient using normal SIP techniques Simple extension

Features Any MIME data can be sent TCP for large messages Routed by existing proxies and registrars Possible to have a different client for IM and communications



Advantages of Using SIP for Presence and IM Unifies Major Communications Services

Voice/video IM Presence

Shared Databases

Shared Proxies

Shared Servers



Advantages of Using SIP For Presence and IM Reduces Management Costs

One infrastructure instead of two One NOC instead of two One set of managers instead of two

Enables New Combined Services Combined services integrate voice, video, IM, presence, web amd email These new services will be a “killer app” for communications on

the Internet Delivery of combined services is greatly simplified by alignment of

presence and communication signaling protocols

Information Resource Jonathan [email protected]

SIP, Presence and Instant Messaging. Spring PIM 2001 SIP, Presence and IM Session Initiation...

Documents

Transcript of SIP, Presence and Instant Messaging. Spring PIM 2001 SIP, Presence and IM Session Initiation...