1. Service Mobility Henning Schulzrinne (with Stefan Berger, Jonathan Lennox, Xiaotao Wu) Columbia University SIP 2003 – January 2003 Paris, France

2. Overview Mobility – more than cell phones Components of service mobility configuration and synchronization discovery Location-based services determining locations for SIP systems call routing and presence services End system service creation Work in progress within Columbia IRT lab

3. Mobility modes Terminal mobility multiple network attachment points, same identifier  IP mobility or SIP registration & re- INVITE User mobility multiple users, same identifier  SIP registration with multiple Contact ’s Session mobility move on-going session to new terminal(s) Service mobility keep same services when moving Mobile services create services on device itself

4. Session mobility Walk into office, switch from cell phone to desk phone call transfer problem  REFER related problem: split session across end devices e.g., wall display + desk phone + PC for collaborative application assume devices (or stand-ins) are SIP- enabled third-party call control

5. Session mobility via 3PCC INVITE speakerphone m=audio c=pc42 INVITE display m=video c=pc42 192.0.2.1 192.0.2.7 INVITE display m=video c=192.0.2.7 m=audio c=192.0.2.1

6. How to find services? Two complementary developments: smaller devices carried on user instead of stationary devices devices that can be time-shared large plasma displays projector hi-res cameras echo-canceling speaker systems wide-area network access Need to discover services in local environment SLP (Service Location Protocol) allows querying for services “find all color displays with at least XGA resolution” SLP in multicast mode SLP in DA mode Need to discover services before getting to environment “is there a camera in the meeting room?” SLP extension: find remote DA via DNS SRV

7. Service mobility Same services, independent of device and network used user address book speed dial entries SIP configuration network preferences (carrier) call handling  already handled by CPL, sip-cgi, servlets, … in home server need remote update capability  SIP PUBLISH In mobile networks, provided by GSM SIM (difficult to move to different devices) HLR in domain domain Need small, portable token for identification temporary device may not be completely trustworthy e.g., airport payphone one-time passwords (OTP) used as key into database (challenge-response) protocol unclear  SIP? LDAP?

8. Service mobility Modes: synchronization good if intermittent connectivity Sync-ML? XPath-based system under development central database works only if permanently connected SIP configuration: get notified if global or device configuration changes (e.g., security update, new end system services) retrieval via HTTP or similar, not SIP partial or full updates related to Internet media guide problem

9. Locations Geographic location latitude, longitude, altitude, velocity, heading Civil location (≠ postal location!) street address, city some countries are a bit difficult… Categorical office, library, theater, hospital, … Behavioral “public location, don't expect privacy” “silence is encouraged, don't ring the phone”

10. Determining locations SIP entities are often far away from physical user or his current network (intentionally) For many devices, can’t afford hardware to determine location different precision requirements: “in Fayette County” (within driving distance of service or person) “on campus” “in room 815” “in corner, talking to Bob” GPS doesn’t work indoors, but Assisted GPS (A-GPS) may Use location beacons: BlueTooth, 802.11 may not offer network connectivity see our 7DS project: offer local content + location Physically close by network entities: DHCP (same broadcast domain) PPP (tail circuit) Not always true with VPNs, but end system knows that it’s using a VPN

11. DHCP for locations Proposal: DHCP extensions for geographic and civil location geographic: resolution (bits), long/lat, altitude (meters or floors) civil: what: end system, switch or DHCP server hierarchical subdivisions, from country to street, landmark name, occupant Also, some LAN switches broadcast port and switch identification CDP for Cisco, EDP for Extreme Networks Can also use backtracking via SNMP switch tables locally implemented for emergency services (Perl sip-cgi script)

12. Location-based services Services: Location-aware call routing “do not forward call if time at callee location is [11 pm, 8 am]” “only forward time-for-lunch if destination is on campus” “contact nearest emergency call center” “do not ring phone if I’m in a theater” “send delivery@pizza.com to nearest branch”delivery@pizza.com Location-based events subscribe to locations, not people “Alice has entered the meeting room” subscriber may be device in room  our lab stereo changes CDs for each person that enters the room Person + location events We’re implementing SIP, caller-preferences and CPL extensions for these services

13. SIP extensions for location-based services Location information is highly sensitive complete tracking of person stalkers and burglars would kill for this information IETF GEOPRIV principle: “target” can control dissemination of location information restrict time of day, information (location, heading, velocity) resolution, number of times queried, destination, retention, … “Alice is in time zone MET” may be ok for strangers, but “Alice is at 41.872833 N, 087.624417 W, heading NE at 45 mph” is not GEOPRIV still defining application scenarios in many cases, easiest to include location information “in-band” with protocol, as this avoids delegating authorization otherwise, need to give access key to database to recipient we propose adding SIP Location header field

14. SIP service interfaces CPL SIP CGI SIP Servlet @ECHO OFFIF %SIP_FROM%==sip:wxt@cs.columbia.edu GOTO BLOCKGOTO EXIT:BLOCKecho SIP/2.0 486 Busy:EXIT <reject status="reject" reason="I don't accept anonymous calls" /> public boolean doInvite(SipRequest req) { SipResponse res = req.createResponse(); res.setStatus(486); res.send(); return true; }

16. #! /usr/bin/env perl -w # Reject messages whose 'From:' matches 'sip:hgs@' by # responding with 486 Busy, redirect the others to voicemail print "SIP/2.0 100 Wait\n\n"; if (defined $ENV{SIP_FROM} && $ENV{SIP_FROM} =~ "sip:hgs@") { print "SIP/2.0 486 Don't disturb, I am working\n\n"; } else { print "SIP/2.0 302 Redirect\n"; print "Contact: sip:xiaotaow\@voicemail.cs.columbia.edu\n\n"; }

17. End system services Techniques for network services are not good for end system services: different service creators end system requirements Currently available: XML-based screen interaction (Cisco) Java applets (Pingtel, 3G phones)

18. Network Services v.s. End System Services

19. Network services End system services Developerexperienced developers non- programmers Media and other end system applications indirect control via SDP direct control User interactionindirectdirect

20. End system service languages Simple and easy to understand by non- programmers Platform neutral Express user interactions Control media and other end system applications Extensible to accommodate new services Restricted to certain class of services, not necessarily Turing-complete

21. Endpoint Service Markup Language (ESML) XML based language Platform and underlying programming language neutral Readable by non-programmers Defined as an XML schema Derivation of new types Pre-defined types Tree-like structure Use packages to group events and actions

22. ESML example <esml name="online_call" require="generic presence ui"> <notification status="online" priority="0.5"> <alert sound=“foo.au" text="Calling xyz@foo.com" />

23. Device agent x10vcr SIP user agent SIP ESML packages Basic user agent GenericMediaUI Presence agent presence conference emailweb calendar im

24. Extend ‘general’ to ‘sip’ <xs:schema targetNamespace="esml:sip" xmlns:sip="esml:sip" xmlns:generic="esml:generic".......... <xs:extension base="generic:IncomingType"> <xs:attribute name="priority" type="PriorityType"/>..........

25. ESML Service Creation

26. Conclusion All SIP devices are mobile but mobility is more than a cell phone integrate devices in environment easier than trying to carry around fewer security issues needs service discovery service mobility remote configuration & synchronization mobile services via end system service creation