fall im 2000 introduction to sip jonathan rosenberg chief scientist
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www.dynamicsoft.comFall IM 2000Introduction to SIP
Introduction to SIP
Jonathan Rosenberg
Chief Scientist
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
Advantages of Using SIP for Presence and IM Unifies Major Communications Services
Voice/video IM Presence
Shared Databases
Shared Proxies
Shared Servers
www.dynamicsoft.comFall IM 2000Introduction to SIP
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
www.dynamicsoft.comFall IM 2000Introduction to SIP
Information Resource Jonathan Rosenberg
[email protected] +1 973 952-5000