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SIP in 2002

SIP in 2002. Henning Schulzrinne Dept. of Computer Science Columbia University. Overview. Where are we? Uses of SIP – new and old Challenges IM 3GPP Security Emergency calling. Where are we?. SIP as the signaling protocol for future applications 3GPP Cable modems (DOCSIS DCS)

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SIP in 2002

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  1. SIP in 2002 Henning Schulzrinne Dept. of Computer Science Columbia University

  2. Overview • Where are we? • Uses of SIP – new and old • Challenges • IM • 3GPP • Security • Emergency calling

  3. Where are we? • SIP as the signaling protocol for future applications • 3GPP • Cable modems (DOCSIS DCS) • IM: AOL interworking, Windows Messenger • but: H.323 dominates videoconferencing, trunk replacement • Proprietary protocols dominate for Ethernet phones • Slow uptake of VoIP

  4. Where are we? • Not quite what we had in mind • initially, for initiating multicast conferencing • in progress since 1992 • still small niche • even the IAB and IESG meet by POTS conference… • then VoIP • written-off equipment (circuit-switched) vs. new equipment (VoIP) • bandwidth is (mostly) not the problem • “can’t get new services if other end is POTS’’  “why use VoIP if I can’t get new services”

  5. Where are we? • VoIP: avoiding the installed base issue • cable modems – lifeline service • 3GPP – vaporware? • Finally, IM/presence and events • probably, first major application • offers real advantage: interoperable IM • also, new service

  6. SIP in the Enterprise • Greenfield • save on wiring and admin expenses • per-seat cost similar ($500+) • Existing installations • small PBX (< 8 lines) cheap • can’t beat $80 phones • move towards multi-cordless (Gigaset, etc.)

  7. Where are we? • Number of robust SIP phones • not yet in Wal-Mart • SIP carriers terminate LAN VoIP • number portability? • 911 • 50+ vendors at SIPit • Building blocks: media servers, unified messaging, conferencing, VoiceXML, …

  8. SIP at Home • Lifeline (power) • Multiple phones per household • expensive to do over PNA or 802.11 • BlueTooth range too short • need wireless SIP base station + handsets • PDAs with 802.11 and GSM? (Treo++) • Incentives • SMS & IM services

  9. SIP phones • Hard to build really basic phones • need real multitasking OS • need large set of protocols: • IP, DNS, DHCP, maybe IPsec, SNTP and SNMP • UDP, TCP, maybe TLS • HTTP (configuration), RTP, SIP • user-interface for entering URLs is a pain • see “success” of Internet appliances • “PCs with handset” cost $500 and still have a Palm-size display

  10. SIP developments in 2001 • SIP revision (“RFC2534bis”) almost done: • semantically-oriented rewrite • layers: message, transport, transaction, transaction user • SDP extracted into separate draft • UA and proxy have the same state machinery • better Route/Record-Route spec for loose routing • no more Basic authentication • few optional headers (In-Reply-To, Call-Info, Alert-Info, …) • Integration of reliable provisional responses and server features • DNS SRV modifications

  11. SIP developments in 2001 • SIP revision backwards compatible • “new” messages work with RFC 2543 implementations • some odd allowed RFC 2543 behavior no longer allowed • CPL almost finished – merger with iCal • sip-cgi published • IM & presence mostly done, except for IM sessions (over TCP) – IMTP, BEEP

  12. SIP developments in 2001 • Work continues on staples: • early media (announcements) • resource reservation (COMET) • SIP security • SIP events • User identification • Call transfer and call control • Now three SIP working groups: • SIP for protocol definition and extensions • SIPPING for applications and “vetting” • SIMPLE for IM & presence

  13. SIP security • Bar is higher than for email – telephone expectations (albeit wrong) • SIP carries media encryption keys • Potential for nuisance – phone spam at 2 am • Safety – prevent emergency calls

  14. SIP security • Exposes weak state of general Internet security tools • Attempt to re-use existing mechanisms: • HTTP digest authentication, with additions to protect crucial headers (e.g., Contact in REGISTER) for e2e and proxy authentication • TLS and IPsec for hop-by-hop authentication and confidentiality • S/MIME for end-to-end

  15. SIP security • Security with random strangers is hard! • Identities are cheap – can’t use for filtering bozos • often only need to verify that same “good” person as before – see ssh • Symmetric (secret) key doesn’t scale • Public key cryptography only modest help • need certification authorities • what is being certified? • CRLs • hard to move keys to new devices – smartcard? • Kerberos needs extensions for interdomain

  16. SIP security – longer term • EAP for authentication (used in 3GPP) • Third-party signatures • “this caller is an employee of Visa” • REFER authentication • Alice (verifiable) asked Bob to call Carol

  17. Other SIP standardization projects • Call history – where has this request been? • Emergency calling (911/112) • universal number: sip:sos@domain • finding the emergency call center • PSTN interoperation • Emergency preparedness • priority access to PSTN and IP resources

  18. Instant message & presence • SIMPLE: MESSAGE, SUBSCRIBE, NOTIFY • Also for various SIP-related events, e.g., in REFER and conferences • Just a special case of event notification: “tell me if something happened” – something happened!

  19. Event notification • Missing new service in the Internet • Existing services: • get & put data, remote procedure call: HTTP/SOAP (ftp) • asynchronous delivery with delayed pick-up: SMTP (+ POP, IMAP) • Do not address asynchronous (triggered) + immediate

  20. Event notification • Very common: • operating systems (interrupts, signals, event loop) • SNMP trap • some research prototypes (e.g., Siena) • attempted, but ugly: • periodic web-page reload • reverse HTTP

  21. SIP event notification • Uses beyond SIP and IM/presence: • Alarms (“fire on Elm Street”) • Web page has changed • cooperative web browsing • state update without Java applets • Network management • Distributed games

  22. SIP doesn’t have to be in a phone

  23. SIP longer-term issues • SDPng? • XML-based generalization • better negotiation and grouping • API standardization • JAIN – servlets • APIs for IM and presence • Operational issues • How to configure 10,000 phones without editing config files?

  24. Conclusion • SIP technology vibrant, with large developer community • Deployments and awareness lag • VoIP as replacement technology – conversion from analog to digital PSTN took decades • Not XML, but will soon be on every desktop

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