1. June 2005SIP for collaboration1 SIP for Collaboration Henning Schulzrinne Columbia University Dept. of Computer Science

2. June 2005 SIP for collaboration2 Overview Evolution from service to protocol to eco-system Quick intro to SIP SIP foundations: sessions, messages, events

3. June 2005 SIP for collaboration3 Philosophy transition One computer/phone, many users One computer/phone, one user Many computers/phones, one user many identifiers anywhere, any time any media right place (device), right time, right media ~ ubiquitous computing mainframe era home phone party line PC era cell phone era Many computers/phones, one user one identifier ~ converged ubiquitous computing & communication

4. June 2005 SIP for collaboration4 Evolution of VoIP “amazing – the phone rings” “does it do call transfer?” “how can I make it stop ringing?” 1996-2000 2000-20032004- catching up with the digital PBX long-distance calling, ca. 1930 going beyond the black phone

5. June 2005 SIP for collaboration5 Collaboration in transition intra-organization; small number of systems (meeting rooms) inter-organization multiple technology generations diverse end points proprietary (single- vendor) systems standards-based solutions

6. June 2005 SIP for collaboration6 Internet services – the missing entry Service/deliverysynchronousasynchronous pushinstant messaging presence event notification session setup media-on-demand messaging pulldata retrieval file download remote procedure call peer-to-peer file sharing

7. June 2005 SIP for collaboration7 Filling in the protocol gap Service/deliverysynchronousasynchronous pushSIP RTSP, RTP SMTP pullHTTP ftp SunRPC, Corba, SOAP (not yet standardized)

8. June 2005 SIP for collaboration8 SIP as service enabler SIP = rendezvous protocol lets users find each other by only knowing a permanent identifier Mobility enabler: personal mobility one person, multiple terminals terminal mobility one terminal, multiple IP addresses session mobility one user, multiple terminals in sequence or in parallel service mobility services move with user

9. June 2005 SIP for collaboration9 A constellation of SIP RFCs Resource mgt. (3312) Reliable prov. (3262) INFO (2976) UPDATE (3311) Reason (3326) SIP (3261) DNS for SIP (3263) Events (3265) REFER (3515) DHCP (3361) DHCPv6 (3319) Digest AKA (3310) Privacy (3323) P-Asserted (3325) Agreement (3329) Media auth. (3313) AES (3853) Non-adjacent (3327) Symmetric resp. (3581) Service route (3608) User agent caps (3840) Caller prefs (3841) ISUP (3204) sipfrag (3240) Security & privacy Configuration Core Mostly PSTN Content types Request routing

10. June 2005 SIP for collaboration10 An eco system, not just a protocol SIP XCAP (config) RTSP SIMPLE policy RPID …. SDP XCON (conferencing) STUN TURN RTP configures initiatescarries controls provide addresses

11. June 2005 SIP for collaboration11 SIP trapezoid outbound proxy a@foo.com: 128.59.16.1 registrar 1 st request 2 nd, 3 rd, … request voice traffic RTP destination proxy (identified by SIP URI domain)

12. June 2005 SIP for collaboration12 SIP message format SDP INVITE sip:bob@there.com SIP/2.0 Via: SIP/2.0/UDP here.com:5060 From: Alice To: Bob Call-ID: 1234@here.com CSeq: 1 INVITE Subject: just testing Contact: sip:alice@pc.here.com Content-Type: application/sdp Content-Length: 147 v=0 o=alice 2890844526 2890844526 IN IP4 here.com s=Session SDP c=IN IP4 100.101.102.103 t=0 0 m=audio 49172 RTP/AVP 0 a=rtpmap:0 PCMU/8000 SIP/2.0 200 OK Via: SIP/2.0/UDP here.com:5060 From: Alice To: Bob Call-ID: 1234@here.com CSeq: 1 INVITE Subject: just testing Contact: sip:alice@pc.here.com Content-Type: application/sdp Content-Length: 134 v=0 o=bob 2890844527 2890844527 IN IP4 there.com s=Session SDP c=IN IP4 110.111.112.113 t=0 0 m=audio 3456 RTP/AVP 0 a=rtpmap:0 PCMU/8000 message body header fields request line request response

13. June 2005 SIP for collaboration13 SIP design objectives new features and services support features not available in PSTN e.g., presence and IM, session mobility not a PSTN replacement not just SS7-over-IP even similar services use different models (e.g., call transfer) client heterogeneity clients can be smart or dumb (terminal adapter) mobile or stationary hardware or software client multiplicity one user – multiple clients – one address multimedia nothing in SIP assumes a particular media type Rosenberg/Schulzrinne: draft-rosenberg-sipping-sip-arch-00

14. June 2005 SIP for collaboration14 SIP architectural principles (1) proxies are for routing do not maintain call state availability scalability flexibility extensibility (new methods, services) end point call state and features dialog models, not call models does not standardize features endpoint fate sharing call fails only if endpoints fail component-based design building blocks call features = notification and manipulation logical components, not physical UA, proxy, registrar, redirect server can be combined into one box Rosenberg/Schulzrinne: draft-rosenberg-sipping-sip-arch-00

15. June 2005 SIP for collaboration15 SIP architectural principles (2) designed for the (large) Internet does not assume particular network topology congestion-controlled deals with packet loss uses core Internet services: DNS for load balancing DHCP for configuration S/MIME for e2e security TLS for channel security generality over efficiency focuses on algorithm efficiency, not constant- factor encoding efficiency “efficiency penalty is temporary, generality is permanent” text encoding extensibility use shim layer for compression where needed allow splitting of functionality for scaling

16. June 2005 SIP for collaboration16 SIP architectural principles (3) separation of signaling and media path followed by media packets independent of signaling path allows direct routing of latency-sensitive media packets (10 ms matters) without constraining service delivery (1s matters) facilitates mobility avoid “hair pinning”, “tromboning” facilitates vertical split between ISP and VSP

17. June 2005 SIP for collaboration17 SIP division of labor proxyB2BUAUA Statestateless transaction- stateful call stateful Headersinspect insert modify (rarely) inspect insert modify inspect reflect Bodiesignore some inspect inspect insert modify inspect Forkyesseparate call legsno Medianomaybeyes Servicesrendezvous call routing call statefulmedia-related

18. June 2005 SIP for collaboration18 Major SIP users VoIP service providers Vonage, 8x8, sipgate.de, fwd, … Internet Multimedia Subsystem (IMS) in 3GPP PacketCable all major cable providers in planning Enterprise all major enterprise IP-PBX vendors interconnection still PSTN

19. June 2005 SIP for collaboration19 SIP devices and software

20. June 2005 SIP for collaboration20 Classical “silo” model +1 201 555 1234 +1 917 555 3210 h323:foo.example.com im:losr32@aol.com home phone, work phone, mobile phone, home email, work email, fax, gmail, AOL, Yahoo, MSN, SMS, sametime, softphone URL, personal 1-800 audio conference, schedule conference, blog, website (C. Jennings)

21. June 2005 SIP for collaboration21 The SIP (converged) model sessionsmessagesevents audio video real-time text MSRP app sharing (text) messages device control shared web browsing INVITE BYE MESSAGE DO PUBLISH SUBSCRIBE NOTIFY call events (transfer) message waiting conference events basic & rich presence calendar data file updates sip:alice@example.com mobility load balancing & redundancy authentication, integrity NAT traversal

22. June 2005 SIP for collaboration22 SIP identity model Old models: no domain authentication  spam, phishing single domain login (e.g., AOL)  no cross-domain authentication PKI with user certificates  expensive, not readily portable Single SIP identity (address-of-record = AOR) simplifies identity assertion and management

23. June 2005 SIP for collaboration23 SIP identity C. Jennings digest authentic ation Challenge INVITE (signed) INVITE 1. Alice calls Bob 2. Outbound proxy verifies that alice@example.com is calling 3. This assertion is signed with the example.com certificate from a well- known certificate authority 4. The foo.com proxy receives this and checks that the signature on the assertion is valid example.com foo.com

24. June 2005 SIP for collaboration24 Presence & communications Presence  facilitate communications availability activities communication privacy choice of media Communications  derive presence “on the phone” typing/composing Presence Communications C. Jennings

25. June 2005 SIP for collaboration25 Presence data model “calendar”“cell”“manual” alice@example.com audio, video, text r42@example.com video person (presentity) (views) services devices

26. June 2005 SIP for collaboration26 Presence data architecture raw presence document create view (compose) privacy filtering draft-ietf-simple-presence-data-model composition policy privacy policy presence sources XCAP (not defined yet) depends on watcher select best source resolve contradictions PUBLISH

27. June 2005 SIP for collaboration27 Presence data architecture candidate presence document watcher filter raw presence document post-processing composition (merging) final presence document difference to previous notification SUBSCRIBE NOTIFY remove data not of interest watcher

28. June 2005 SIP for collaboration28 Rich presence extensions derived from sensors, human input, calendars

29. June 2005 SIP for collaboration29 Service creation programmer, carrier end user network servers SIP servlets, sip-cgi CPL end systemVoiceXMLVoiceXML (voice), LESS Tailor a shared infrastructure to individual users traditionally, only vendors (and sometimes carriers) learn from web models

30. June 2005 SIP for collaboration30 XCON System Logical XCON Server Floor Control Client TEMPLATE Of the SYSTEM: Pre-configured Initial/Default values Conf Event Notification Server Focus CPCP Client CCCP Client CPCP Server CCCP Server Call Signaling Client TEMPLATE Policy: Of TYPE RULES RESERVATION Policy: Of TYPE RULES CURRENT Policy: Of TYPE RULES RESERVATION Of the INSTANCE: Of TYPE CONFERENCE-INFO STATE Of the CURRENT INSTANCE: Of TYPE CONFERENCE-INFO Notification Client Floor Control Server SIP/ PSTN/ H.323 T.120/ Etc. CCCP CPCP SIP NOTIFY/ Etc. BFCP Logical XCON Client

31. June 2005 SIP for collaboration31 Conclusion Avoid silo model Collaboration needs sessions, messages and events plus stored context and asynchronous collaboration  Wikis, blog, conference recordings, structured data stores, shared calendars, … SIP addresses multi-modal communication needs Need more than basic presence automatically derived, not user input