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www.dynamicsoft.com IM 2000 -- May 24, 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.

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Presentation on theme: "www.dynamicsoft.com IM 2000 -- May 24, 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist."— Presentation transcript:

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2 IM May 24, 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist

3 IM May 24, 2000 Introduction to SIP Talk Outline Brief Introduction on SIP SIP As a Platform for Presence Requirements of a presence protocol Requirements of an IM protocol Components SIP already provides What else is needed in SIP

4 IM May 24, 2000 Introduction to SIP Introducing - 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 Invitation of users to sessions Find the users current location, match will their capabilities and preferences, in order to deliver invitation Carry opaque session descriptions Modification of sessions Termination of sessions

5 IM May 24, 2000 Introduction to SIP Introducing - Session Initiation Protocol (SIP) cont. Main Features Personal mobility services Wide area operation Session independence voice, video, games, chat, virtual reality, etc. Leverages other Internet protocols

6 IM May 24, 2000 Introduction 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 + UAS

7 IM May 24, 2000 Introduction to SIP Protocol Components cont. 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

8 IM May 24, 2000 Introduction to SIP SIP Architecture Request Response Media SIP Client SIP Redirect Server SIP Proxy SIP Client (User Agent Server) Location Service 13 14

9 IM May 24, 2000 Introduction to SIP Benefits of SIP Scalability Proxy servers can be stateless Features pushed to the periphery of the network UDP Extensibility Numerous capabilities built in for extensibility New headers New methods New bodies Protocol mechanics exist to determine common operating sets

10 IM May 24, 2000 Introduction to SIP Benefits of SIP cont. Modularity SIP based on a component model for systems Complete solution built by piecing together independent but cooperative protocols SIP provides a general purpose mechanism for rendezvous to enables communications

11 IM May 24, 2000 Introduction to SIP Components of a Presence Solution Subscription Means to subscribe to some entity Requires huge scalability Distributed subscription state Lightweight transactions Authentication of subscribers Ability to convey complex subscription rules Routing and namespace partitioning

12 IM May 24, 2000 Introduction to SIP Components of a Presence Solution cont. Publication 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

13 IM May 24, 2000 Introduction to SIP Components of a Presence Solution cont. Notification 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 Ideally, push notifications to the client

14 IM May 24, 2000 Introduction to SIP SIP and Presence/IM are Closely Related SIP Requires Presence State to Route Calls from A to B SIP and presence protocol use same data But SIP is asynchronous; presence protocol is synchronous SIP and Presence Share Similar Scalability Requirements SIP can handle more than phone calls - supports all types of sessions Namespace partitioning for scale Stateless/UDP operation for scale Fast in the core, smart at the edge model needed in both cases

15 IM May 24, 2000 Introduction to SIP SIP and Presence/IM are Closely Related cont. SIP and Presence Share Similar Security Requirements End-to-end authentication of messages and responses Not mandatory Hop by Hop encryption and authentication for privacy and authentication transitivity to achieve scale

16 IM May 24, 2000 Introduction to SIP SIP and Presence/IM are Closely Related cont. SIP and Presence/IM Both Require Routing Difficult part of IM is finding user to deliver IM Difficult part of SIP is finding user to deliver session invitation Presence also requires same routing - finding presence server for user SIP and presence/IM share similar extensibility requirements Core communications services Broad uses Wide area services

17 IM May 24, 2000 Introduction to SIP SIP and Presence/IM are Cousins cont. SIP and presence/IM share similar content carriage requirements SIP and presence will need to carry a common data format SIP carries SDP Presence carries presence data format IM needs to support MIME SIP provides MIME

18 IM May 24, 2000 Introduction 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

19 IM May 24, 2000 Introduction to SIP Requirements for SIP to Support Presence Define New Entity -- Presence Server Possibly co-located with registrar Extend with New SUBSCRIBE Method SIPs Routing, naming, security, content, transaction labeling and sequencing capabilities are all required Define distributed subscription state Similar to mailing lists

20 IM May 24, 2000 Introduction to SIP Requirements for SIP to Support Presence cont. Extend with New NOTIFY Method Create Mechanism to Fetch Friend Lists REGISTER response? Need not be a SIP mechanism Define Presence URL

21 IM May 24, 2000 Introduction to SIP Requirements for SIP to Support IM cont. Possible Approaches IM is a session, established with INVITE IM is a messaging service Would need new SIP method IM as a Session Supportable with SIP now New RTP payload format for text Allows tight synchronization with voice and video One character at a time readily supported Similar to chat

22 IM May 24, 2000 Introduction to SIP Requirements for SIP to Support IM cont. IM as a Messaging Service No session setup needed Ordering not important Simplifies storage for later delivery All messages need to travel through servers, rather than be sent directly to user No notion of session over which lifetime of an address exists Can be easily done using new method, MESSAGE

23 IM May 24, 2000 Introduction to SIP Advantages of Using SIP for Presence and IM Unifies Major Communications Services Voice/video IM Presence Shared Databases Shared Proxies Shared Servers

24 IM May 24, 2000 Introduction to SIP Advantages of Using SIP For Presence and IM cont. 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, These new services will be killer app for communications on the Internet Delivery of combined services is greatly facilitated by alignment of presence and communication signaling protocols

25 IM May 24, 2000 Introduction to SIP Information Resource Jonathan Rosenberg


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