SIP: Status and Directions

Transcription

1 1 SIP: Status and Directions Henning Schulzrinne Dept. of Computer Science Columbia University New York, New York Bell Atlantic January 26, 2000

2 2 Overview SIP overview/review SIP services SIP standardization status SIP bake-off Columbia Internet telephony activities SIP for notification SIP for mobility

3 3 Architecture MG MGC Internet circuit-switched voice (POTS, ISDN) proxy GK GK proxy gateway PSTN RTP circuit-switched voice SIP H.323 Megaco/MGCP/MDCP

4 4 SIP 101 SIP = signaling protocol for establishing sessions/calls/conferences/... session = audio, video, game, chat, called server may map name to user@host 2. callee accepts, rejects, (! forward new address) 3. if new address, go to step 1 4. if accept, caller confirms 5....conversation caller or callee sends BYE

5 5 SIP Operation in Proxy Mode cs.columbia.edu cs.tu-berlin.de 1 INVITE 200 OK 7 2 henning? hgs@play location server 3 4 INVITE hgs@play 200 OK 6 5 play 8 ACK henning@columbia.edu tune 9 ACK hgs@play 10 media stream

6 6 SIP Operation in Redirect Mode ieee.org? location server tu-berlin.de 4 1 INVITE henning@ieee.org 302 Moved temporarily Contact: hgs@columbia.edu 2 henning columbia.edu ACK henning@ieee.org INVITE hgs@columbia.edu columbia.edu OK ACK hgs@columbia.edu hgs

7 7 SIP Advanced Features operation over UDP or TCP multicast invitations basic ACD interactive web response (IWR) UA $ proxy = proxy/redirect $ proxy/redirect stateless proxies: self-routing responses forking proxies: call several in sequence and/or parallel security: basic (password), digest (challenge/response), PGP

8 8 More SIP Internet Telephony Services camp-on without holding a line short message service ( instant messaging ) schedule call into the future call with expiration date add/remove parties to/from call mesh buddy lists can support CLASS features (see tech report) call transfer under discussion

9 9 Internet Telephony as Part of Internet address = SIP address SIP URLs in web pages forward to , web page, chat session,... include web page in invitation response ( web IVR ) RTSP: choose your own music-on-hold include vcard, photo URL in invitation

10 10 SIP Security signaling re-uses existing implementations and protocols! bugs less likely: IPsec SSL basic digest pgp hop-by-hop hop-by-hop SIP plaintext password authentication SIP challenge-response p SIP PGP encryption/authentication for parts/all p p media: IPsec RTP negotiation via SDP key in SDP ( k= )

11 11 Interdomain Communications and Security no difference in protocol betwen intra/inter domain any proxy server can insist on Proxy-Authentication intermediaries can sign requests and responses (e.g., this phone belongs to a Bell Atlantic employee )

12 12 SIP Extensibility headers that receiver may ignore, e.g., Photo new methods and inquire about those supported (OPTIONS) features that receivers needs to understand: Required! Unsupported e.g., Required: com.sylantro.feature proposed: features supported via Supported header

13 13 An IETF VoIP Architecture RTSP server voice prompts record message RTSP LDAP SIP SIP server RADIUS sip-cgi CPL accounting server MGCP/MEGACOP RTP DIAMETER? COPS? MG firewall

14 14 SIP Voice Mail RTSP server media player voice prompts record message PLAY SETUP PLAY ogm RECORD msg INVITE SIP server URL or media create URL entry for voice message SIP RTSP

15 15 Chatterbox Cafe IP Centrex ISP PSTN Ralph s Pretty Good Grocery IP Heads Up Barber Internet

16 eligible for Draft Standard: 6 months, 2 implementations p 16 SIP Standardization Status Feb. 2, 1999: IETF Proposed Standard March 17, 1999: IETF RFC 2543 new SIP working group (move from mmusic) working on updated draft based on implementation experience mostly clarifications + optional headers, no new version

17 17 SIP Work Items sip-cgi call processing language (CPL) reliable provisional (1xx) responses caller preferences third-party call control SIP for subscribe/notify SIP ISUP interworking SIP H.323 interworking billing reverse channel setup for call progress tones pre-ringing resource reservation server feature negotiation

18 18 SIP Bake-Off 3 bake-offs: April, August, December from 15 to 33 groups hardware, PSTN gateways, proxy/redirect servers, clients, test instrument,...

19 19 SIP Bake-Off Participants 3Com dynamicsoft Mitel 8x8 Ellemtel Netspeak Agilent Ericsson Nortel Alcatel Facet Nuera Broadsoft Helsinki Univ. OZ.com British Telecom Hewlett-Packard Pingtel Catapult Indigo Radcom Cisco IPcell Telogy Columbia University Lucent Vovida Dialogic MCI Worldcom VTEL Mediatrix

20 20 SIP Bake-Off Goals basic call set-up registration, user location proxies and redirect server operation advanced features: security identify implementation bugs and robustness issues identify spec ambiguities

21 21 SIP Bake-Off Results almost all implementations could establish basic calls either on arrival or after minor on-site fixes tested redirection, proxying, security, registration,... generated interoperability test cases and tools will fold clarifications into Draft revision of RFC and web page at hgs/sip install public testing mechanisms (Pulver OpenTestNet,

22 22 On-Going Columbia IP Telephony Projects e*phone: Ethernet SIP phone sipc SIP user agent for Windows, Linux, Solaris,... sipd SIP server SIP-H.323 translation SIP/RTSP unified messaging SIP gateways to the telephone network (T1 E&M, ISDN,...) SIP mobility programming servers: CPL, sip-cgi

23 23 On-Going Columbia IP Telephony Projects light-weight resource reservation: YESSIR resource-reservation aggregation: BGRP charging for resource reservations: RNAP TRIP telephony gateway routing QOS fault detection

24 24 Planned Internet Telephony Projects detailed security evaluation/implementation caller preferences implementation service creation environments for end users and admins SIP for notification ( buddy lists ) interaction of signaling and QOS SIP and ISUP 911 services

25 25 e*phone stand-alone Ethernet phone will full SIP implementation

26 sipc 26

27 27 sipd SIP registrar, proxy and redirect server: user registration forking proxy capability: one call, many destinations security mechanisms (basic, digest, pgp) for authentication sip-cgi: interface to scripting languages caller preferences CPL in progress

28 28 Integrating Signaling and Instant Messaging: Some Ideas reverse signaling: callee indicates availability buddy lists = special case of event notification other events: sensor 17 smells smoke, Beanie Babies are on sale, (voice) mail has arrived,... subscribe notify set up call useful for call parking many SIP mechanisms apply: security, redirection, proxying, content negotiation,...

29 29 SIP for Event Notification add two methods: SUBSCRIBE and NOTIFY proxy server may intercept SUBSCRIBE use message body for event description default: presence, indicated by REGISTER one of many proposals for presence (IETF WG!)

30 30 subscriber Alice Bob SIP for Event Notification SUBSCRIBE NOTIFY SUBSCRIBE proxy SUBSCRIBE NOTIFY REGISTER publisher Carol

31 31 Mobility new network new IP address (DHCP) mobile IP hides addr. changes but: little deployment : encapsulation overhead : dog-legged routing CH data data home network CN FA HA tunnelled data MH MH CH HA HA mobile host correspondent host router with home agent functionality router with foreign agent functionality : IP address filtering MH data foreign network

32 32 SIP Mobility Overview pre-call mobility SIP proxy, redirect mid-call mobility SIP re-invite, RTP recovery from disconnection

33 33 MH acquires IP address via DHCP SIP Mobility: Pre-call optional: MH finds SIP server via multicast REGISTER MH updates home SIP server CH redir home network MH MH CH redir mobile host correspondent host SIP redirect server SIP INVITE SIP 302 moved temporarily SIP INVITE SIP OK optimization: hierarchical LR (later) MH foreign network 5 data

34 34 SIP mobility: mid-call redir home network MH MH CH redir mobile host correspondent host SIP redirect server MH!CH: new IN- VITE, with Contact and updated SDP CH SIP INVITE SIP OK data re-registers with home registrar MH MH foreign network

35 35 SIP mobility: multi-stage registration Don t want to bother home registrar with each move San Francisco From: alice@ny Contact: CA From: alice@ny Contact: alice@ca NY Los Angeles From: alice@ny Contact: REGISTER INVITE

36 36 SIP basic standard stable Conclusion multiple interoperating implementations backward-compatible features: interoperation with legacy signaling systems mobility caller preferences call transfer... programming of services: cgi, CPL, applets

37 37 For more information... SIP: RTP: hgs/rtp Papers: