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SIP – growing up

SIP – growing up. Henning Schulzrinne Columbia University SIP 2003 – January 2003 Paris, France. Overview. What happened in 2002? standards milestones deployment Outlook for 2003 substantial completion? SIP challenges. What happened in 2002?. New revision of SIP RFCs published

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SIP – growing up

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  1. SIP – growing up Henning Schulzrinne Columbia University SIP 2003 – January 2003 Paris, France

  2. Overview • What happened in 2002? • standards milestones • deployment • Outlook for 2003 • substantial completion? • SIP challenges

  3. What happened in 2002? • New revision of SIP RFCs published • RFC 3261: basic protocol specification • RFC 3262: Reliability of Provisional Responses • RFC 3263: Locating SIP Servers • RFC 3264: An Offer/Answer Model with the Session Description Protocol (SDP) • RFC 3265: SIP-specific Event Notification

  4. RFC 3261 • Backward compatible with RFC 2543 – no new version • Major changes: • specification behavior-oriented, not header-oriented • e.g., separation into ‘layers’ • mandate support for UDP and TCP • formal offer/answer model for media negotiation • uses both SRV and NAPTR for server location, load balancing and redundancy • much more complete security considerations • “sips:’’ for secured (TLS) path • PGP removed due to lack of use • Basic authentication removed as unsafe • S/MIME added for protecting message bodies (and headers, via encapsulation) • Route/Record-Route simplified

  5. SIP and 3G wireless networks • In July, 3GPP adopts SIP as signaling protocol for Release5 • increased collaboration between organizations • still somewhat different perspectives:

  6. SIP adoption in 2002 • IBM, Novell support SIMPLE for group communications in the enterprise • but still confusion by Microsoft: MSN Messenger 5.0 (no SIP) vs. Windows Messenger 4.7 (SIP + MSN, but mostly for XP) • AOL backing off from interoperability • IETF adds Jabber to the IM standards confusion • PRIM and APEX fading • 3GPP adopts SIMPLE as IM/presence mechanism for Release6 • commercial services for consumers and businesses • Vonage, Denwa, eStara, … • MCI Worldcom, DeltaThree

  7. Still no cheap (< $100) phones, but getting closer snom 100 ($270), Cisco 7905 ($165), Teledex (but not all SIP yet…) but still not Wal-Mart  video-conferencing equipment still lacking turn-key “IP PBX-in-a-box” available from multiple vendors many good software clients PDA clients emerging despite industry “issues”, robust set of participants at SIP products

  8. SIP standardization in 2002 • Probably point of maximum activity for SIP work • There have been at least (in my collection of 6428 distinct IETF I-Ds)… • 210 distinct I-Ds with –sip– (not counting -00, -01, etc.) • 83 with –sipping– • 34 with –simple– • Current status somewhat difficult to track • not all WG I-Ds are draft-ietf-* • many drafts start as draft-somebody-* • IETF draft tracking is iffy (complete only after WG done) • JAIN activities in 2002: • SIP servlet API • JAIN SIP lite

  9. Other SIP RFCs published in 2002 • DHCP options for SIP servers • The Session Initiation Protocol (SIP) UPDATE Method • Integration of Resource Management and Session Initiation Protocol (SIP) • Internet Media Type message/sipfrag • A Privacy Mechanism for the Session Initiation Protocol (SIP) • Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks • Session Initiation Protocol (SIP) Extension for Instant Messaging • The Reason Header Field for the Session Initiation Protocol (SIP) • Session Initiation Protocol (SIP) Extension Header Field for Registering Non-Adjacent Contacts • User Requirements for the Session Initiation Protocol (SIP) in Support of Deaf, Hard of Hearing and Speech-impaired Individuals • Session Initiation Protocol for Telephones (SIP-T): Context and Architectures • Short Term Requirements for Network Asserted Identity • Integrated Services Digital Network (ISDN) User Part (ISUP) to Session Initiation Protocol (SIP) Mapping

  10. Conferencing conference creation – ad-hoc and pre-arranged call leg events  conference membership tracking floor control = SIP events + SOAP Application interaction DTMF control (instead of INFO, complementary to RFC 2833) e.g., KPML for causing HTTP POST on digit combinations User identity via S/MIME Debugging and call history Content indirection Emergency calls Presence and IM: session mode (INVITE-initiated) UPDATE for presence updates is-composing event while typing limit message size delivery confirmation more detailed presence status SIMPLE Java APIs Major SIP standardization items left to do

  11. SIP standardization • After this, mostly into maintenance mode • track bugs and eventually issue RFC 3261bis • Will SIP progress to Draft Standard? • hardly unique: • 883 Proposed Standard RFCs, 99 Draft Standard, 66 Standard • unlikely  too many external dependencies (TLS, S/MIME, SRV, NAPTR, …) • lots of work (interop statements)  too little motivation

  12. Is SIP still simple? • 25 SIP RFCs (+ SDP), 823 pages • and the call flows RFCs aren’t out yet  • RFC 3261 is longest RFC ever • by bytes, RFC 2801 (IOTP) wins by page count • However… • probably only (3GPP) proxy writers need to worry about most of these • can still build a simple user agent in a (long) evening • most effort is likely to be for security: • TLS, digest, S/MIME, AAA, … • DOS protection

  13. What has SIP become? • Session Initiation Protocol – 2 out of 3 words are wrong (or too narrow…) • Plesiosynchronous end-to-end message delivery • with real-time confirmation (unlike email) • but modest rates (unlike RTP) • either as session or stand-alone (“page-mode”) • Rendezvous: find end point via abstract address • Components for specific functionality: • session setup and negotiation: INVITE, UPDATE, OPTIONS, ACK, INFO, BYE, PRACK • event notification sessions: SUBSCRIBE, NOTIFY • page-mode message delivery: MESSAGE • binding management: REGISTER • Transport: from UDP  UDP + TCP  TCP + SCTP + UDP

  14. General VoIP infrastructure • One cannot build a service on SIP alone • Other items still need work: • AAA for SIP, both RADIUS (widely used, but obsolete) and DIAMETER • security infrastructure • how to authenticate to callee? • cheap identities  even PKI mainly helps to identify caller on second call • use OPTION to get callee certificate? • configuration of SIP devices: • configuring by keypad is a pain • configuration by web page doesn’t scale • tftp is insecure and for LAN only • need configuration for identities, protocol parameters

  15. Aside: SIP phone QoS • We measured mouth-to-ear one-way delay of a range of commercial SIP phones and software applications, in a LAN

  16. IP Emergency (911/112) services DHCP 500 W 120th Room 815 MAC  port “911” CDP: port 17, cepsr-7-1 INVITE sip:sos@cs.columbia.edu Location: 500 W 120, Rm. 815 tel:911 500 W 120 jurisdictional directory

  17. SIP security infrastructure • need to store secret in semi-trusted devices • single sign-on? • CINEMA system: • i-button or magnetic swipe card • sets up lines on phone • controls environment • all via SIP events • but phone configuration via screen faking dim lights SIP events add “line” change station

  18. SIP work at Columbia • Location-based services • Event models and filtering • Mesh-based conferencing • End system service creation (CPL extension) • Service discovery

  19. Conclusion • SIP standardization nearing completion • core functionality sufficient to build • 3G mobile system • corporate PBX • but need more operational experience • efforts still telephony-centric, but combinations IM + VoIP emerging • architectural model for “what’s-SIP-good-at” emerging, but different visions

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