14-05-2013, 11:55 AM
SIP, Presence and Instant Messaging
SIP.ppt (Size: 695.5 KB / Downloads: 14)
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
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
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