IM 2000 -- May 24, 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.
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Transcript of IM 2000 -- May 24, 2000 Introduction to SIP Jonathan Rosenberg Chief Scientist.
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction to SIP
Introduction to SIP
Jonathan Rosenberg
Chief Scientist
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 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 + UAS
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction to SIP
SIP ArchitectureRequest
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.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction to SIP
Requirements for SIP to Support Presence Define New Entity -- Presence Server
Possibly co-located with registrar
Extend with New SUBSCRIBE Method SIP’s Routing, naming, security, content, transaction labeling and
sequencing capabilities are all required Define distributed subscription state
Similar to mailing lists
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction 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
www.dynamicsoft.comIM 2000 -- May 24, 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.comIM 2000 -- May 24, 2000Introduction 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, email 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
www.dynamicsoft.comIM 2000 -- May 24, 2000Introduction to SIP
Information Resource Jonathan Rosenberg
[email protected] +1 732.741.7244