Fall IM 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.

www.dynamicsoft.comFall IM 2000Introduction to SIP

Introduction to SIP

Jonathan Rosenberg

Chief Scientist


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 plus UAS


Protocol Components cont. Redirect Server

Network server - redirects users to try other server

Proxy Server Network server - a proxy 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


Requirements for Presence and IM

Subscription Ask for notifications of changes in communications state Routing request to server that knows state of a user

Notification Propagate state changes to subscribers

Publication Tell the network about my changes in state


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

Client

Client

Client

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

Offline Subscriptions Handled

Presence server always asks user if a subscription should be accepted


Features of SIP For Presence Extension cont. Multiple Entities Can Generate Presence Information for One

Presentity Mobile phone, PDA, laptop and desktop PC

Multiple Presence Clients Can Be Online at Once

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 Associates an IM with an existing call 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 Rosenberg

[email protected] +1 973 952-5000

Fall IM 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.

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Transcript of Fall IM 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.