1. SIP and Services 1 Blindsiders May 99 Lucent Technologies - Proprietary SIP A Platform for Providing Integrated Services Jonathan Rosenberg Bell Laboratories May 27, 1999 http://www.dnrc.bell-labs.com/~jdrosen/papers/blindsiders99_sip.ppt

2. SIP and Services 2 Blindsiders May 99 Lucent Technologies - Proprietary Talk Outline SIP Overview –History –Technology SIP Server as a Service Platform Example integrated services SIP CGI for service creation CPL for service creation Future Directions

3. SIP and Services 3 Blindsiders May 99 Lucent Technologies - Proprietary Introducing - Session Initiation Protocol (SIP) Developed in mmusic group in IETF –Proposed standard RFC2543, Feb. 1999 –Work began 1995 –Part of Internet Multimedia Conferencing Suite Main functions –Invitation of users to sessions Find the users current location to deliver invitation Carry opaque session descriptions –Modification of sessions –Termination of sessions Main Features –Personal mobility services –Wide area operation –Session independence voice, video, games, chat, virtual reality, etc. –Leverages other Internet protocols

4. SIP and Services 4 Blindsiders May 99 Lucent Technologies - Proprietary 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 + UAS Redirect Server –Network server; redirects users to try other server Proxy Server –Network Server Proxies request to another server Can fork request to multiple servers, creating a search tree Registrar –receives registrations regarding current user locations

5. SIP and Services 5 Blindsiders May 99 Lucent Technologies - Proprietary SIP Architecture 1 2 3 4 5 6 7 8 9 10 11 12 SIP Client SIP Redirect Server SIP Proxy SIP Client (User Agent Server) Location Service Request Response 13 14 Media

6. SIP and Services 6 Blindsiders May 99 Lucent Technologies - Proprietary SIP Message Syntax Many header fields from http New ones (Also, Replaces, Via) are SIP specific Payload contains a media description SDP - Session Description Protocol INVITE sip:ann@lucent.com SIP/2.0 From: J. Rosenberg Subject: SIP will be discussed, too To: A. Netravali Call-ID: 1997234505.56.78@122.3.44.12 Content-type: application/sdp CSeq: 4711 INVITE Content-Length: 187 v=0 o=user1 53655765 2353687637 IN IP4 128.3.4.5 s=Mbone Audio i=Discussion of Mbone Engineering Issues e=mbone@somewhere.com c=IN IP4 224.2.0.1/127 t=0 0 m=audio 3456 RTP/AVP 0

7. SIP and Services 7 Blindsiders May 99 Lucent Technologies - Proprietary Why SIP on the Internet? Wide Area Scalability –Stateless to call-state aware servers –Single UDP port to TCP connection per transaction –Simplicity = faster processing Interoperability –Textual encoding –parsimonious on sending, gracious on receiving –Simplicity UAC assigned as HW project –18 implementations at bakeoff Extensibility –Textual encoding –Extension feature negotiation –Distributed development

8. SIP and Services 8 Blindsiders May 99 Lucent Technologies - Proprietary Services, services, services! IP telephony cost benefits to consumer declining Must be differentiators –higher quality –ease of use - UI –new services and features Key is new services –integration services email, web, presence, IM, chat part of telephony –control services allow parameters to be defined by consumer –presentation services new look and feel for old friends

9. SIP and Services 9 Blindsiders May 99 Lucent Technologies - Proprietary SIP Server Primary place for SIP services Service Classes –routing services –rejection/redirection services –logging/notification services Integration –add web, email, chat, to all of the above SIP Server Service Logic Requests Responses Service Logic Interface

10. SIP and Services 10 Blindsiders May 99 Lucent Technologies - Proprietary Why SIP for Integration? MIME –Uses MIME types as payloads –Can carry anything HTML, VXML… URIs –Uniform Resource Identifiers –Internet mechanism for naming resources http://www.bell-labs.com mailto:jdrosen@bell- labs.com tel:5551212 –SIP uses URIs for all addresses DNS –Uses DNS SRV records for server resolution –Same mechanism as email routing

11. SIP and Services 11 Blindsiders May 99 Lucent Technologies - Proprietary Interactive Web Response user calls a number SIP server fetches content, returns to caller web page answers use hyperlinks instead of keypresses to navigate –much easier than voice final link makes phone call INVITE http content Web Page INVITE OK

12. SIP and Services 12 Blindsiders May 99 Lucent Technologies - Proprietary Interactive Content Response IWR: what if its not a PC? Use SIP MIME handling –Gateways indicate support for VXML –PCs indicate support for HTML –Server returns based on client capabilities Cross platform INVITE http content Web Page ICR Service INVITE VXML PSTN GW

13. SIP and Services 13 Blindsiders May 99 Lucent Technologies - Proprietary Personalized Web Agents (PWA) A calls B B is not home After N rings, A gets web page instead –possibly dynamically created for caller Thanks, Joe, for calling regarding Sales Deal –lists alternate contact information/times email, voicemail URLs INVITE Web Page

14. SIP and Services 14 Blindsiders May 99 Lucent Technologies - Proprietary Web Caller ID Calling Party Service –When A calls B, Bs homepage appears in As browser –homepage dynamically generated for A perhaps Called Party Service –When A calls B, As homepage appears in Bs browser –Traditional direction SIP INVITE http GET As page A B 200 OK Web Server

15. SIP and Services 15 Blindsiders May 99 Lucent Technologies - Proprietary Transfer To Web A calls B A and B talk –subject of conversation is some web page B hangs up, transfers A to page As browser jumps to page SIP INVITEA B 200 OK Web Server Transfer http://…. http GET Web page

16. SIP and Services 16 Blindsiders May 99 Lucent Technologies - Proprietary Email E-mail not good for interactive communications Great for notification related services! –Type of information unbounded Notification possibilities –call information –subscriber information monthly bill –network information special offer! –Messaging emails contain URLs to streaming media controls

17. SIP and Services 17 Blindsiders May 99 Lucent Technologies - Proprietary Email Ringback A calls B Server checks access lists –A is on email ringback list Server converts SIP INVITE to email, places As SIP URL there Server rejects call –includes text in body saying B alerted by email B gets email, can call back A by clicking on link Can also use IM! SIP INVITE 400 w/ text SMTP A B IMAP SIP INVITE 200 OK SIP Server Mail Server

18. SIP and Services 18 Blindsiders May 99 Lucent Technologies - Proprietary Email Call Logs A calls B server rings B, B not home server returns error to A server generates email call log for B –time, date of call –caller, subject, priority –URL for returning call SIP INVITE 400 not home SMTP A B SIP Server Mail Server SIP INVITE

19. SIP and Services 19 Blindsiders May 99 Lucent Technologies - Proprietary Redirect to Email A calls B server notices A is on access list for service Redirects caller to mailto URL Callers mail tool starts, with To, Subject filled in INVITE SIP Server 300 Send email Contact: mailto:jack@att.net Check access list

20. SIP and Services 20 Blindsiders May 99 Lucent Technologies - Proprietary Call Filtering to Email Similar to previous Server lets some calls proceed –based on priority –based on caller –based on time of day Others are redirected to email –personal email for personal calls –business email for others INVITE SIP Server 300 Send email Check access list INVITE Caller A Caller B Called Party

21. SIP and Services 21 Blindsiders May 99 Lucent Technologies - Proprietary Presence ICQ concept –buddy lists and subscriptions –know who is online –normally for instant messages Big idea: Users can subscribe to each other, and learn: –when they pick up and hang up the phone –when they are available to talk or not –when they are in the office or not chair sensor! –when the cell-phone is on or not Presence propagates information about a users willingness, ability, and desire to communicate using a variety of mediums

22. SIP and Services 22 Blindsiders May 99 Lucent Technologies - Proprietary Example Presence Service Phone status subscription –A subscribes to Bs phone –When Bs phone state changes hook state willingness to talk –Notification sent to A email, instant message, presence notification –A can then call B unsubscribe to B SUBSCRIBE hangup NOTIFY Presence server

23. SIP and Services 23 Blindsiders May 99 Lucent Technologies - Proprietary SIP and Presence SIP Server = Presence Server! –SIP server knows users location SIP REGISTER method Any URL - email, http, pager –Presence namespace = SIP namespace –Presence service can be transparent REGISTER NOTIFY SIP/Presence Server

24. SIP and Services 24 Blindsiders May 99 Lucent Technologies - Proprietary Presence Standards Instant Messaging and Presence Protocol (IMPP) Working Group –IETF wg –currently doing requirements Internet Standard for IMPP SIP is a proposal for the presence protocol

25. SIP and Services 25 Blindsiders May 99 Lucent Technologies - Proprietary Caller Controls In PSTN, caller has little control on call handling SIP Caller Preferences –Service Preferences –Routing Preferences Service Prefs –line hunt vs. ring all –forward vs. redirect Routing preferences –reach home address –reach cell phone –reach line where English spoken –reach line with voicemail Caller and callee preferences combined –feature interaction!

26. SIP and Services 26 Blindsiders May 99 Lucent Technologies - Proprietary Challenge - Service Programmability Where do services live? What controls do the programs have? When can the program execute controls? What information are the programs provided? What resources do the programs have access to? Who can create the programs? How are the programs instantiated?

27. SIP and Services 27 Blindsiders May 99 Lucent Technologies - Proprietary Location of logic SIP User Agents –trust issues –heterogeneity of platforms –always on problem SIP servers –natural place for routing, screening, pre- call services External devices to SIP servers –SCP/SSP model in IN safety, load balancing, good for third parties latency issues in IP –what replaces INAP? DIAMETER? COPS? MGCP+? SIP (same syntax, wrong semantics)

28. SIP and Services 28 Blindsiders May 99 Lucent Technologies - Proprietary Nature of C/I Highest level –new call from Joe to Bob –forward call –can be SP independent Medium level –state machine transitions + basic data (caller, callee, etc.) Lowest level –Full messages Not a single answer! –Fundamental tradeoffs: simplicity vs. flexibility safety vs. flexibility

29. SIP and Services 29 Blindsiders May 99 Lucent Technologies - Proprietary Who can write them? Creator determines tradeoff operating point Three principals –Administrator –Third party provider –End user Lines can be blurry Real operating point depends largely on trust

30. SIP and Services 30 Blindsiders May 99 Lucent Technologies - Proprietary Other issues Access to resources –What else can program do besides control –General purpose program - anything –Java script - lots, but not everything –configuration script - very limited How does it get there? –Linked in (API model) server must be taken down, recompiled not clean –separate process (CGI) –data read in (servlet model)

31. SIP and Services 31 Blindsiders May 99 Lucent Technologies - Proprietary CGI Model Server receives request Server spawns separate process Request passed to script –headers in env. Variables –body on stdin Script generates body of response –sends on stdout Script terminates Server sends response Web Server Script Process HTTP GET 200 OK ENV + stdin stdout

32. SIP and Services 32 Blindsiders May 99 Lucent Technologies - Proprietary SIP CGI Benefits of CGI as a basis –programming language independence –full control over headers/messages –leverage existing tools –SIP similar to HTTP Whats different from HTTP CGI –persistence model –multiple actions per script output –response naming –request naming

33. SIP and Services 33 Blindsiders May 99 Lucent Technologies - Proprietary Example Output INVITE sip:jdrosen@bell-labs.com SIP/2.0 To: sip:jdrosen@bell-labs.com From: sip:machine@bell-labs.com Call-ID: 10 Cseq: 0 INVITE Content-Length: 0 PROXY_REQUEST_TO sip:hgs@cs.columbia.edu SIP/2.0 Max-Forwards: SIP/2.0 180 Ringing User CGI_SCRIPT_COOKIE aoi988ans0naa SIP/2.0

34. SIP and Services 34 Blindsiders May 99 Lucent Technologies - Proprietary Status Draft 1 submitted to IETF Dec98, draft 2 May 21, 1999 No wg to do it –likely we will submit as informational Two known implementations

35. SIP and Services 35 Blindsiders May 99 Lucent Technologies - Proprietary Solution II: CPL Call Processing Language –targeted for end user service creation –controls at high level –information available at high level –Describes basic service Model: SIBs from IN –service = DAG –Two types of nodes action nodes: outputs = results decision nodes: ouputs = possible values –Safety –Bounds on compute time

36. SIP and Services 36 Blindsiders May 99 Lucent Technologies - Proprietary Example DAG String Switch field = From Proxy to joe@att.com Proxy to voicemail Proxy to 555-1212 Boss@company.com otherwise No answer Busy No answer Call

37. SIP and Services 37 Blindsiders May 99 Lucent Technologies - Proprietary Representation Use XML –links = subtags –parameters = attributes –extensibility mechanisms useful –easy transport –generation/parsing by tools GUI for creation <location url=sip:voicemail@att.com link=vm>

38. SIP and Services 38 Blindsiders May 99 Lucent Technologies - Proprietary Implementation Status gosSIP server platform –SIP server –CGI, CPL, other programming interfaces –Access to other IP services (planned) http, smtp, ldap, diameter –Platform for integrated service creation gossip Server Mail Services IM and Presence Services Directory Services Conference Services Web Services

39. SIP and Services 39 Blindsiders May 99 Lucent Technologies - Proprietary Conclusions Integrated Services key Many ways in which email, web, presence, IM, chat can work with voice SIP a natural platform –IP friendly - URIs, MIME –Scalable, interoperable, simple CPL/CGI for service creation Future work –New Programmability models Java servlets DIAMETER –Presence and IM –SIP to IN call model mappings (w/ INU)