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SIP for IP Communications. Jonathan Rosenberg Chief Scientist. IP Communications. “Communications” consists of more than just voice video IM presence wireless Presence and IM are of particular interest Question for discussion: What is SIP’s role in presence and IM?.

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sip for ip communications

SIP for IP Communications

Jonathan Rosenberg

Chief Scientist

ip communications
IP Communications
  • “Communications” consists of more than just voice
    • video
    • IM
    • presence
    • wireless
  • Presence and IM are of particular interest
  • Question for discussion:
    • What is SIP’s role in presence and IM?
presence today
Also Known as Buddy Lists

Indicates Online/Offline Status

Used Largely to Enable IM

Users Subscribe to “Friends” List

When User is Online

Click to send instant message

Initiate voice chat (newer)

When Friends Log On/Off, Notifications are Sent

User Status Can Sometimes Be Indicated

Busy, not at my desk


Presence Server







Presence Today
presence today cont
Presence Today cont.
  • No Standard for IM or Presence
  • Many Players (i.e., AOL, Yahoo and Tribal Voice)
    • Each with its own, non-interoperable system
  • User’s Experience is Limited
    • Metcalfe’s Law
    • Running many different applications
  • IETF IMPP Group Tasked to Develop a Standard Solution
  • Proposals Solicited for a Complete Solution at April 2000 Meeting
  • A SIP Solution was Submitted
    • Co-authors from dynamicsoft, Microsoft, Cisco and Columbia University
components of a presence solution

Definition: to subscribe to some entity

Requires massive scalability

Distributed subscription state

Lightweight transactions

Authentication of subscribers

Ability to convey complex subscription rules

Routing and namespace partitioning

Components of a Presence Solution
components of a presence solution cont

Enables a user to send information to server for distribution

Must be possible to have multiple entities publish for a single address

My cell phone

My IM client

Describes communications means, state, capabilities and characteristics

Components of a Presence Solution cont.
components of a presence solution cont1

Rapid delivery of published data to subscribers

Makes use of distributed subscription state

Highly scalable

Presence data changes often

Many subscribers

Must be able to convey a variety of presence data formats

Components of a Presence Solution cont.
session initiation and presence im share requirements
Network Awareness of Presence State

SIP for call routing

Presence for distribution to subscribers

Real-Time Delivery

Forwarding to Server Responsible for a Specific User


Session Initiation and Presence/IM Share Requirements
session initiation and presence im share requirements cont


Access controls


Carriage of MIME Data


Session Initiation and Presence/IM Share Requirements cont.
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


Audio,video - MIME capability






SIP Already Provides Publication Capability
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





Presence Agent +

Proxy/Registrar =

Presence Server



SIP Extension for Presence
features of sip for presence extension
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
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
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




Shared Databases

Shared Proxies

Shared Servers

Advantages of Using SIP for Presence and IM
advantages of using sip for presence and im1
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

Advantages of Using SIP For Presence and IM
new service example traffic jam alerts
Uses Geographic Locale as Presence Component

Mobile phone site location


Service Definition

Turn on mobile phone in car

As you drive, application server monitors location

As you approach traffic, service will call you

Voice response system reads out alternate route

New Service Example: Traffic Jam Alerts


Application Server


Presence Server


new service example auto conference calls
Problem: Difficult to juggle busy people’s schedules to set up audio conference calls

Solution: use presence to set up the call when everyone is available


Enter email addresses into a web form (1)

Application subscribes to users (2)

When all are online, application calls each participant, calls a conference bridge, connects them together

New Service Example: Auto Conference Calls

Conference Server






SIP Calls

information resource
Information Resource
  • Jonathan Rosenberg
    • +1 973.952.5000