Service Mobility

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 Contacts
• 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 maudio cpc42
192.0.2.1
INVITE display mvideo c192.0.2.7 maudio c192.0
.2.1
INVITE display mvideo cpc42
192.0.2.7
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, cant 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 doesnt 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 its 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 Im in a theater
• send delivery_at_pizza.com to nearest branch
• 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
• Were 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
lt?xml version"1.0" ?gt lt!DOCTYPE cpl PUBLIC
"-//IETF//DTD RFCxxxx CPL 1.0//EN" "cpl.dtd"gt
ltcplgt ltincominggt ltaddress-switch
field"origin" subfield"user"gt
ltaddress is"anonymous"gt ltreject
status"reject" reason"I don't
accept anonymous calls" /gt lt/addressgt
lt/address-switchgt lt/incominggt lt/cplgt
_at_ECHO OFF IF SIP_FROMsipwxt_at_cs.columbia.edu
GOTO BLOCK GOTO EXIT BLOCK echo SIP/2.0 486
Busy EXIT

• CPL
• SIP CGI
• SIP Servlet

public boolean doInvite(SipRequest req)
SipResponse res req.createResponse()
res.setStatus(486) res.send() return
true
15
(No Transcript)
16
! /usr/bin/env perl -w Reject messages whose
'From' matches 'siphgs_at_' by responding with
486 Busy, redirect the others to voicemail print
"SIP/2.0 100 Wait\n\n" if (defined
ENVSIP_FROM ENVSIP_FROM "siphgs_at_")
print "SIP/2.0 486 Don't disturb, I am
working\n\n" else print "SIP/2.0 302
Redirect\n" print "Contact sipxiaotaow\_at_voice
mail.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 v.s. End System Services
Network services End system services
Developer experienced developers non-programmers
Media and other end system applications indirect control via SDP direct control
User interaction indirect direct
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

• ltesml name"online_call"
• require"generic presence ui"gt
• ltnotification status"online"
• priority"0.5"gt
• ltaddress-switch field"origin"gt
• ltaddress is"xyz_at_foo.com"gt
• ltcall /gt
• ltalert soundfoo.au"
• text"Calling xyz_at_foo.com" /gt
• lt/addressgt
• lt/address-switchgt
• lt/notifyinggt
• lt/esmlgt

23
ESML packages
email
web
im
conference
calendar
24
Extend general to sip

• ltxsschema targetNamespace"esmlsip"
• xmlnssip"esmlsip"
• xmlnsgeneric"esmlgeneric"
• ..........
• ltxscomplexType name"IncomingType"gt
• ltxscomplexContentgt
• ltxsextension
• base"genericIncomingType"gt
• ltxsattribute name"priority"
• type"PriorityType"/gt
• ..........
• lt/xsextensiongt
• lt/xscomplexContentgt
• lt/xscomplexTypegt

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