Ubiquitous SIP

1
Ubiquitous SIP

• Henning Schulzrinne
• (with Stefan Berger, Stelios Sidiroglou, Kundan
  Singh, Xiaotao Wu, Weibin Zhao and the RPIDS
  authors)
• Columbia University IRT Lab
• TU Darmstadt/NEC/U Karlsruhe/NSF RI July 2003

2
Overview

• What is ubiquitous computing?
• Core ubiquitous communications functionality
• Brief introduction to SIP
• Ubiquitous computing in SIP and SLP
• On-going work at Columbia

3
What is ubiquitous computing?

• Ubiquitous computing has as its goal the
  enhancing computer use by making many computers
  available throughout the physical environment,
  but making them effectively invisible to the
  user. (Weiser, 1993)
• Ubiquitous computing is not virtual reality, it
  is not a Personal Digital Assistant (PDA) such as
  Apple's Newton, it is not a personal or intimate
  computer with agents doing your bidding. Unlike
  virtual reality, ubiquitous computing endeavers
  to integrate information displays into the
  everyday physical world. It considers the nuances
  of the real world to be wonderful, and aims only
  to augment them. (Weiser, 1993)

4
Ubiquitous computing aspects

• Also related to pervasive computing
• Mobility, but not just cell phones
• Computation and communications
• Integration of devices
• borrow capabilities found in the environment ?
  composition into logical devices
• seamless mobility ? session mobility
• adaptation to local capabilities
• environment senses instead of explicit user
  interaction
• from small dumb devices to PCs
• light switches and smart wallpaper

5
Components of ubiquitous communications

• Service discovery ? discover devices
• Service mobility ? configuration information
  moves to new devices
• Event notification ? for context awareness
• Context-awareness ? location, user actions,
  location properties,

6
Example ubicomp projects

• Ambient Devices
• EU IST Disappearing Computer
• Project Aura, CMU ? user attention
• UNC office of real soon now
• augmented surfaces Reki99
• Microsoft Easy Living
• Oxygen, MIT
• Portolano, Univ. of Washington
• Endeavour, Berkeley
• CoolTown, HP Labs

7
Ubiquitous computing using SIP whats different?

• Traditionally, focus on closed environments (lab,
  single company, home, )
• Often, proprietary protocols ? self-contained
  environment
• Here,
• operate across Internet (? no Corba)
• trusted, semi-trusted and untrusted participants
• use standard protocol mechanisms where possible
• make minimal assumptions on homogeneity
• respect user privacy

8
What is SIP?

• Session Initiation Protocol ? protocol that
  establishes, manages (multimedia) sessions
• also used for IM, presence event notification
• uses SDP to describe multimedia sessions
• Developed at Columbia U. (with others)
• Standardized by IETF, 3GPP (for 3G wireless),
  PacketCable
• About 60 companies produce SIP products
• Microsofts Windows Messenger (4.7) includes SIP

9
Basic SIP message flow
10
SIP trapezoid
11
SIP event notification

• Named events
• Typically, used for events within conferences
  (Alice joined) and call legs (e.g., call
  transfer)
• Supports arbitrary notification bodies, typically
  XML

SUBSCRIBE sipalice_at_vmail.example.com SIP/2.0 To
ltsipalice_at_example.comgt From ltsipalice_at_example.c
omgttag78923 Call-Id 1349882_at_alice-phone.example
.com Contact ltsipalice_at_alice-phone.example.comgt
NOTIFY sipalice_at_alice-phone.example.com
SIP/2.0 Event message-summary Subscription-Stat
e active Messages-Waiting yes Message-Account
sipalice_at_vmail.example.com Voice-Message 2/8
(0/2)
12
SIP event architecture

• Does not try to route notifications (application
  layer multicast) as in SIENA
• Filtering at PA under discussion (for
  low-bandwidth devices)
• rate
• content
• But most ubicomp notification groups are probably
  small
• and message volume not likely to provide much
  bandwidth saving via network-based filtering
• Greatly simplifies trust model no intermediaries
  that need to inspect content
• can encrypt via S/MIME
• However, can build redistribution exploders and
  list subscriptions (subscribe to
  engineering_at_hp.com)

13
SIP presence architecture
REGISTER
SUBSCRIBE
watcher
PA
Alice
NOTIFY
Bob
lt?xml version"1.0" encoding"UTF-8"?gt ltppresence
xmlnsp"urn" entity"presalice_at_example
.com"gt ltptuple id"sg89ae"gt ltpstatusgt
ltpbasicgtopenlt/pbasicgt lt/pstatusgt
ltpcontactgttel09012345678lt/pcontactgt lt/ptuplegt
lt/ppresencegt
PUAs
PUBLISH
14
Session mobility

• Walk into office, switch from cell phone to desk
  phone
• call transfer problem ? SIP 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

15
Session mobility via 3PCC
pc42
INVITE speakerphone maudio cpc42
192.0.2.1
INVITE pc42 mvideo c192.0.2.7 maudio c192.0.2.
1
INVITE display mvideo cpc42
192.0.2.7
16
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//example.com/SrvRqst?public?typeprinter
• 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

17
Service Location Protocol (SLP)

• Version 2 standardized June 1999

SrvRqst
SA
UA
SA
SrvRply
SrvReg
DA
SrvReg
SrvRqst
DAAdvert
18
SLP attribute example
URL serviceprinterlpr//igore.wco.ftp.com/draft
scope-list Development
Language tag en
Attributes (NameIgore),(DescriptionFor developers only), (ProtocolLPR),(location-description12th floor), (OperatorJames Dornan \3cdornan_at_monster\3e), (media-sizena-letter),(resolutionres-600),x-OK
19
Other service location mechanism

• DNS SRV/NAPTR
• DNS TXT records (Apple Rendezvous) ? DNS-SD
• UPnP uses SSDP
• multicast HTTP over UDP

M-SEARCH HTTP/1.1 S uuidijklmnop-7dec-11d0-a76
5-00a0c91e6bf6 Host 239.255.255.250reservedSSDPp
ort Man "ssdpdiscover ST gefridge MX
3 HTTP/1.1 200 OK S uuidijklmnop-7dec-11d0-a765
-00a0c91e6bf6 Ext Cache-Control no-cache"Ext",
max-age 5000 ST gefridge USN
uuidabcdefgh-7dec-11d0-a765-00a0c91e6bf6 AL
ltblenderixlgtlthttp//foo/bargt
20
Service mobility

• Allow access to service parameters anywhere
  payphone problem
• address book
• incoming call rules
• source name (SIP From)
• Existing solutions
• SIM card ? cumbersome to change
• synchronization (e.g., Palm) ? not suitable for
  borrowed devices
• Server-based services ? easier with SIP
  (service-routing), if carrier allows
• Emerging solutions for SIP systems
• Small user token (smart card, RFID, i-button)
  identifying user
• Temporarily download configuration from home
  server

21
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

22
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

23
DHCP for locations

• modified dhcpd (ISC) to generate location
  information
• use MAC address backtracing to get location
  information

24
Determining locations

• For many devices, cant afford hardware to
  determine location
• Implementing BlueTooth-based location sensor
  networks
• CU 7DS project offer local content location
• Developing programmable active badges with IR and
  RF capabilities

25
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)

26
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

27
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

28
RPIDS rich presence data

• Basic IETF presence (CPIM) only gives you
• contact information (SIP, tel URI)
• priority
• open or closed
• Want to use presence to guide communications

watcher
everything
PA
PUA
watcher
"vague"
PUBLISH
watcher
NOTIFY
CPL
INVITE
29
Aside SIP caller preferences

• SIP core philosophy many devices, one identifier
• Address people, not plastic

30
Aside SIP caller preferences

• But caller sometimes has preferences among
  devices
• SIP caller guides call routing
• I hate voicemail!
• I hate people!
• I prefer voicemail
• Multilingual lines
• Caller proposes, callee disposes

sipisabel_at_a.comlanguages"es" sipisabel_at_a.coml
anguages"en"q0.2
INVITE sipsales_at_a.com Accept-Contact
languages"en"
REGISTER
INVITE
sipbob_at_a.comlanguages"en"
31
RPID Rich presence data

• Integrates caller preferences information into
  presence announcements
• ltactivitygt on-the-phone, away, appointment,
  holiday, meal, meeting, steering, in-transit,
  travel, vacation, busy, permanent-absence
• ltplacetypegt home, office, public
• ltprivacygt public, private, quiet
• ltfromgt, ltuntilgt status validity
• ltidlegt activity for device
• ltrelationshipgt family, associate, assistant,
  supervisor
• ltclassgt grouping

32
RPID example

• lttuple id"7c8dqui"gt
• ltstatusgt
• ltbasicgtopenlt/basicgt
• ltcontactgtsipsecretary_at_example.comlt/contactgt
• ltcapcapabilitiesgt ltcapfeature
  name"Media"gt
• ltcapvaluegtvoicelt/capvaluegt
• ltcapvalue negated"true"gtmessagelt/capval
  uegt
• lt/capfeaturegt
• lt/capcapabilitiesgt
• lt/statusgt
• lteprelationshipgtassistantlt/eprelationshipgt
• ltnotegtMy secretarylt/notegt
• lt/tuplegt

33
Event filtering

• Events are core attribute of ubiquitous computing
  systems
• tell devices about people actions
• tell people about device presence
• e.g., Alice has entered Room 815
• devices that know Alices preferences subscribe
  to Alice
• locations may also have presence
• e.g., for occupancy sensors, switches

34
Location filtering language

• SIP presence information will be updated using
  REGISTER and UPDATE
• Need to constrain
• who is allowed to see what detail ? presentity
  privacy
• who wants to see what detail
• how often
• what granularity of change
• Proposal to allow SUBSCRIBE to include frequency
  limitation
• Working on CPL-like language invoked (logically)
  at publication time
• classes of users, e.g., based on entry in my
  address book
• classes get mapped to restriction
• 12 bits of long/lat resolution, 6 bits of
  altitude resolution, 0 bits of velocity
• time zone only, category only
• watchers can then add filters that restrict the
  delivery
• location difference gt threshold
• entering or leaving certain area
• entering or leaving category or behavioral type

35
Columbia SIP servers (CINEMA)
Telephone switch
Local/long distance 1-212-5551212
rtspd media server
Quicktime
Single machine
RTSP
sipconf Conference server
RTSP clients
Department PBX
sipum Unified messaging
Internal Telephone Extn 7040
713x
sipd Proxy, redirect, registrar server
SQL database
SIP/PSTN Gateway
Web based configuration
SNMP (Network Management)
Extn 7134
H.323
Extn 7136
siph323 SIP-H.323 translator
NetMeeting
xiaotaow_at_cs
36
Location-based services in CINEMA

• Initial proof-of-concept implementation
• Integrate devices
• lava lamp via X10 controller ? set personalized
  light mood setting
• Pingtel phone ? add outgoing line to phone and
  register user
• painful needs to be done via HTTP POST request
• stereo ? change to audio CD track based on user
• Sense user presence and identity
• passive infrared (PIR) occupancy sensor
• magnetic swipe card
• ibutton
• BlueTooth equipped PDA
• IRRF badge (in progress)
• RFID (future)
• biometrics (future)

37
CINEMA system
38
All-SIP implementation
39
Service creation

• Promise of faster service creation
• traditionally, only vendors (and sometimes
  carriers)
• learn from web models

programmer, carrier end user
network servers SIP servlets, sip-cgi CPL
end system VoiceXML VoiceXML (voice), LESS
40
sip-cgi

• web common gateway interface (cgi)
• oldest (and still most commonly used) interface
  for dynamic content generation
• web server invokes process and passes HTTP
  request via
• stdin (POST body)
• environment variables ? HTTP headers, URL
• arguments as POST body or GET headers
  (?arg1var1arg2var2)
• new process for each request ? not very efficient
• but easy to learn, robust (no state)
• support from just about any programming language
  (C, Perl, Tcl, Python, VisualBasic, ...)
• Adapt cgi model to SIP ? sip-cgi
• RFC 3050

41
sip-cgi examples

• Block _at_vinylsiding.com
• if (defined ENVSIP_FROM ENVSIP_FROM
  "sip_at_vinylsiding.com")
• print "SIP/2.0 600 I can't talk right
  now\n\n"
• Make calls from boss urgent
• if (defined ENVSIP_FROM ENVSIP_FROM
  /sipboss_at_mycompany.com/)
• foreach reg (get_regs())
• print "CGI-PROXY-REQUEST reg SIP/2.0\n"
• print "Priority urgent\n\n"

42
Call Processing Language (CPL)

• XML-based language for processing requests
• intentionally restricted to branching and
  subroutines
• no variables (may change), no loops
• thus, easily represented graphically
• and most bugs can be detected statically
• termination assured
• mostly used for SIP, but protocol-independent
• integrates notion of calendaring (time ranges)
• structured tree describing actions performed on
  call setup event
• top-level events incoming and outgoing

43
CPL

• Location set stored as implicit global variable
• operations can add, filter and delete entries
• Switches
• address
• language
• time, using CALSCH notation (e.g., exported from
  Outlook)
• priority
• Proxy node proxies request and then branches on
  response (busy, redirection, noanswer, ...)
• Reject and redirect perform corresponding
  protocol actions
• Supports abstract logging and email operation

44
CPL example
45
CPL example

• lt?xml version"1.0" ?gt
• lt!DOCTYPE call SYSTEM "cpl.dtd"gt
• ltcplgt
• ltincominggt
• ltlookup source"http//www.example.com/cgi-bin
  /locate.cgi?userjones"
• timeout"8"gt
• ltsuccessgt
• ltproxy /gt
• lt/successgt
• ltfailuregt
• ltmail url"mailtojones_at_example.comSubjec
  tlookup20failed" /gt
• lt/failuregt
• lt/lookupgt
• lt/incominggt
• lt/cplgt

46
CPL example anonymous call screening

• 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

47
Service creation a comparison
API servlets sip-cgi CPL
language-independent no Java only yes own
secure no mostly can be yes
end user service creation no yes power users yes
GUI tools no no no yes
Multimedia some yes yes yes
call creation yes no no no
48
Service creation for presence services
(work-in-progress)

• Accept or deny subscriptions
• Shape presence notifications
• different level of detail for family, friends and
  colleagues
• particularly important for geo data
• Subscriber can filter detail
• primarily, wireless bandwidth constraints
• rate limit notifications
• XPath?
• Mostly, condition/reaction ? CPL can be extended
  to most of these functions

49
Pushing context-sensitive data to users

• User with mobile device should get location
  information when entering city, campus or
  building
• flight and gate information
• maps and directions
• local weather forecast
• special advisories (choose security checkpoint
  2)
• Often does not require knowing user
• but interface with (e.g.) calendar
• Example Columbia implementation
• OBEX data exchange over BlueTooth
• PDA pushes current appointment or event name
• base station delivers directions and map

50
Conclusion

• SIP auxiliary protocols supports many of the
  core requirements for ubiquitous computing and
  communications
• mobility modalities terminal, user, session,
  service
• service negotiation for devices with different
  capabilities
• automatic configuration and discovery
• with SLP or similar
• event notification and triggered actions
• automatic actions event filtering, CPL, LESS
  (for end system services)
• SIP offers a loosely-coupled approach (cf. Jini
  or object models)
• Also need data push functionality
• Avoid tendency to assume SIP users are human
  want to interconnect different components and
  devices
• SIP device configuration needs automation, rather
  than screen-scraping