Internet Telecom Expo September 20, 2000 SIP vs. H.323 SIP vs. H.323 Will the Real IP Telephony Please Stand Up? Jonathan Rosenberg Chief Scientist

Internet Telecom Expo September 20, 2000 SIP vs. H.323 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 users current location, match with their capabilities and preferences in order to deliver invitation Carry opaque session descriptions Modification of sessions Termination of sessions

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Session Initiation Protocol (SIP) cont. Main Features Personal mobility services Wide area operation Session flexibility Voice; video; games; chat; virtual reality; etc. Leverages other Internet protocols

Internet Telecom Expo September 20, 2000 SIP vs. H.323 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

Internet Telecom Expo September 20, 2000 SIP vs. H.323 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

Internet Telecom Expo September 20, 2000 SIP vs. H.323 SIP Architecture Request Response Media SIP Client SIP Redirect Server SIP Proxy SIP Client (User Agent Server) Location Service 13 14

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Primary Advantages Extensibility Flexibility Scalability New Services

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Extensibility Primary Goal: Ensure Baseline Operation Always Works Maintain backward compatibility Numerous Ways to Extend New Optional Headers New Mandatory Headers Negotiation to common set New Methods New Body Types Extensions are Named Registered with IANA com.example.feature naming convention

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Flexibility SIP is a Protocol Component, not a Complete Solution Does not Specify Codecs Media Transport Routing Exchanges Database Billing Records Does not specify architectures Does not specify services Result: Service Providers can Build the Network They Want, not the one the Standard Body Wants

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Scalability Internet Model for Scalability Fast and simple in the core Smarter towards the periphery Example: RSVP vs. Diffserv SIP Uses Internet Model Stateless fast proxies in the core Stateful proxies at the periphery Call-stateful proxies at the edge CSF Proxy Edge Periphery Core SF Proxy SF Proxy SF Proxy SF Proxy SL Proxy CSF SF SL Call Stateful Stateful Stateless

Internet Telecom Expo September 20, 2000 SIP vs. H.323 How SIP Enables New Services Fundamental Strengths SIP leverages the power of web and URLs for Addresses MIME bodies routing It therefore, works well with these applications Technical Proof Points Caller ID with vCards Caller ID with JPEG Transfer to Web Web IVR

Internet Telecom Expo September 20, 2000 SIP vs. H.323 Information Resource Jonathan Rosenberg