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Ubiquitous-UPenn Powered By Docstoc

                Henning Schulzrinne
   (with Knarig Arabshian, Stefan Berger, Stelios
Sidiroglou, Kundan Singh, Xiaotao Wu, Weibin Zhao
              and the RPIDS authors)
            Columbia University IRT Lab
         Univ. of Pennsylvania – February 2004
   What is ubiquitous computing?
   Core ubiquitous communications
   Brief introduction to SIP
   Ubiquitous computing in SIP and SLP
   On-going work at Columbia
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)
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
       from small dumb devices to PCs
            light switches and smart wallpaper
Components of ubiquitous
   Service discovery  discover devices
   Service mobility  configuration
    information moves to new devices
   Event notification  for context
   Context-awareness  location, user
    actions, location properties, …
Example “ubicomp” projects
   Ambient Devices
   EU IST Disappearing Computer
   Project Aura, CMU  user
   UNC “office of real soon now”
   augmented surfaces [Reki99]
   Microsoft Easy Living
   Oxygen, MIT
   Portolano, Univ. of Washington
   Endeavour, Berkeley
   CoolTown, HP Labs
Ubiquitous computing using SIP –
what’s different?
   Traditionally, focus on closed environments
    (lab, single company, home, …)
   Often, proprietary protocols  self-contained
   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
Context-aware communications
   Traditional emphasis: communicate anywhere, anytime, any media 
    largely possible today
   New challenge: tailor reachability
   Context-aware communications
        modify when, how, where to be reached
         machine: context-dependent call routing
         human: convey as part of call for human usage
   context-aware services
        leveraging local resources
        awareness of other users
   sources of location information
        voluntary and automatic
   location-based services  privacy concerns
        applies to other personal information
        activity, reachability, capabilities, bio sensor data, …
   emergency services as a location-based service
      context = “the interrelated conditions in
       which something exists or occurs”
      anything known about the participants in
       the (potential) communication relationship
      both at caller and callee

time                     CPL
capabilities             caller preferences
location                 location-based call routing
                         location events
activity/availability    presence
sensor data (mood, bio) not yet, but similar in many
                        aspects to location data
What is SIP?
      Session Initiation Protocol  protocol
       that establishes, manages (multimedia)
          also used for IM, presence & event
          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
      Microsoft’s Windows Messenger (4.7)
       includes SIP
Basic SIP message flow
SIP trapezoid
      outbound proxy

                       SIP trapezoid

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
     To: <>
     From: <>;tag=78923
     Contact: <>

     NOTIFY SIP/2.0
     Event: message-summary
     Subscription-State: active

     Messages-Waiting: yes
     Voice-Message: 2/8 (0/2)
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
       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”)
        SIP presence architecture


Alice                                                                        Bob
                                          <?xml version="1.0" encoding="UTF-8"?>
                                          <p:presence xmlns:p="urn:…"
         PUAs     PUBLISH                        entity="">
                                          <p:tuple id="sg89ae">
Session mobility
   Walk into office, switch
    from cell phone to desk
       call transfer problem 
        SIP REFER
   related problem: split
    session across end
       e.g., wall display + desk
        phone + PC for
        collaborative application
       assume devices (or
        stand-ins) are SIP-
       third-party call control
       Session mobility via 3PCC
                        INVITE speakerphone

          INVITE pc42

                        INVITE display
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://
        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
Service Location Protocol (SLP)
   Version 2 standardized June 1999

                SrvRply             SA


      SrvRqst              SrvReg

      SLP attribute example
URL          service:printer:lpr://
scope-list   Development
Language tag en
Attributes   (Name=Igore),(Description=For developers
             only), (Protocol=LPR),(location-
             description=12th floor), (Operator=James
             Dornan \3cdornan@monster\3e), (media-
Other service location mechanism
   DNS TXT records (Apple Rendezvous)  DNS-SD
   UPnP uses SSDP:
       multicast HTTP over UDP

    M-SEARCH * HTTP/1.1
    S: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6
    Man: "ssdp:discover“
    ST: ge:fridge
    MX: 3

    HTTP/1.1 200 OK
    S: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6
    Ext: Cache-Control: no-cache="Ext", max-age = 5000
    ST: ge:fridge
    USN: uuid:abcdefgh-7dec-11d0-a765-00a0c91e6bf6
    AL: <blender:ixl><http://foo/bar>
Service mobility
   Allow access to service parameters anywhere – “payphone
        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
   Emerging solutions for SIP systems:
        Small user token (smart card, RFID, i-button) identifying user
        Temporarily download configuration from home server
Context-based communication
   Observable state and actions
   State:
       location of users
       user activities
   Derive state from
       sensors (time, location, environment, user interaction)
       data (calendars, address books)
       network inputs (messages)
   Actions
       incoming and outgoing calls
       incoming and outgoing IMs, SMS, email, …
   Initially, focusing on location at key context
Location-based services
   Finding services based on location
       physical services (stores, restaurants, ATMs, …)
       electronic services (media I/O, printer, display, …)
       not covered here
   Using location to improve (network) services
       communication
           incoming communications changes based on where I am
       configuration
           devices in room adapt to their current users
       awareness
           others are (selectively) made aware of my location
       security
           proximity grants temporary access
   Privacy rules for access to context data
Location-based services
   Presence-based approach:
       UA publishes location to presence agent (PA)
       becomes part of general user context
       other users (human and machines) subscribe to
           call handling and direction
           location-based anycast (“anybody in the room”)
           location-based service directory
   Languages for location-based services
       building on experience with our XML-based service
        creation languages
       CPL for user-location services
       LESS for end system services
Location-based SIP 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 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
   We’re implementing SIP, caller-preferences and CPL
    extensions for these services
   Geographic location
       latitude, longitude, altitude, velocity, heading
   Civil location (≠ postal location!)
       time zone, 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”
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
Determining location
   Two types of sensors:
       end system determines location
            “handset-based”  GPS, 802.11 triangulation
       network conveys location to end system or other component
            MAC backtracking
            AP-based 802.11 triangulation
            swipe cards, iButtons, active badges
   Two modes:
       explicit user action: swipe card, touch iButton
       involuntary: network-based tracking
   GPS may not be practical (cost, power, topology)
   Add location beacons
       extrapolate based on distance moved
            odometer, pedometer, time-since-sighting
       idea: meet other mobile location beacons
            estimate location based on third-party information
Determining locations
     For many devices, can’t
      afford hardware to
      determine location
         Implementing BlueTooth-
          based location sensor
         CU 7DS project: offer local
          content + location
     Developing programmable
      active badges with IR and
      RF capabilities
    DHCP for locations
       modified dhcpd (ISC) to generate location information
       use MAC address backtracing to get location information



8:0:20:ab:d5:d  458/17

                                             DHCP answer:
                                             sta=DC loc=Rm815
                                             lat=38.89868 long=77.03723

                        458/17  Rm. 815
                        458/18  Rm. 816
Location-based services & SIP
   We’re using SIP (and SIMPLE) as generic
    protocols for
       effecting change (“actuators”)
           send MESSAGE to devices
       distributing event information (“sensors”)
   Advantages:
       people and rooms identified by URIs
       cross-domain, with extensive security mechanisms
           domains don’t need to trust each other
       scalable to global system
           many other systems are mostly local
Architectures for (geo)
information access
   Claim: all using protocols fall into one of these categories
   Presence or event notification
      “circuit-switched” model
      subscription: binary decision
   Messaging
      email, SMS
      basically, event notification without (explicit) subscription
      but often out-of-band subscription (mailing list)
   Request-response
      RPC, HTTP; also DNS, LDAP
      typically, already has session-level access control (if any at
   Presence is superset of other two
SIP URIs for locations
                              location beacon

   Identify confined
    locations by a SIP URI,
    Register all users or
                                                          Contact: bob

    devices in room                                    

   Allows geographic
    anycast: reach any
                                                      Contact: alice

    party in the room                           Room 815
RPID: 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

    PUA                       PA                 watcher   "vague"

                                        NOTIFY   watcher          CPL

Aside: SIP caller preferences
 SIP core philosophy: many devices, one identifier
 Address people, not plastic
       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”
Accept-Contact: *;languages="en"


RPID: Rich presence data
   Integrates caller preferences information into
    presence announcements
   <activity>: on-the-phone, away, appointment,
    holiday, meal, meeting, steering, in-transit, travel,
    vacation, busy, permanent-absence
   <placetype>: home, office, public
   <privacy>: public, private, quiet
   <sphere>: facet of life (home, work, …)
   <idle>: activity for device
   <relationship>: family, associate, assistant,
   <class>: grouping
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 Alice’s preferences subscribe
             to Alice
       locations may also have presence
            e.g., for occupancy sensors, switches
Location filtering language
   SIP presence information will be updated using REGISTER and
   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 > threshold
              entering or leaving certain area
              entering or leaving category or behavioral type
      Presence model


subscriber (watcher)

       for each
              event generator                                    change to previous
                  policy                                            notification?
                                                  rate limiter

Policy rules
   There is no sharp geospatial boundary
   Presence contains other sensitive data
    (activity, icons, …) and others may be
   Example: future extensions to personal
    medical data
       “only my cardiologist may see heart rate,
        but notify everybody in building if heart
        rate = 0”
   Thus, generic policies are necessary

              publication   location     notification   location
 target       interface                  interface                  GEOPRIV
                             server                     recipient

                            presence                                SIP
presentity                                              watcher
             PUBLISH         agent                                  presence

 caller                                                  callee     SIP
               INVITE                    INVITE                     call
           Columbia SIP servers (CINEMA)
Local/long distance             Telephone
1-212-5551212                   switch                                      rtspd: media server         Quicktime
                                                        Single machine
                                                                                                       RTSP clients
                                Department        Conference server
                                PBX                                                     Unified
  Telephone                                                                             messaging
                  713x                      sipd:
  Extn: 7040
                                            Proxy,                         SQL
                                            redirect,                    database              Web
                                            registrar                                         server
         SIP/PSTN Gateway                                                                                 Web based
           Extn: 7134                                                 Management)

                       Extn: 7136                                                            H.323
                                                                      SIP-H.323                        NetMeeting
                      xiaotaow@cs                                     translator
Location-based services in
   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
        IR+RF badge (in progress)
        RFID (future)
        biometrics (future)
         Example: user-adaptive device
                                                  “all devices that are in the building”
                                                  RFC 3082?
                802.11 signal      SLP
             strength  location
  To: 815cepsr
  Contact: alice@cs

                       PA          SUBSCRIBE
                                   to each room

1. discover room URI                                                            SIP
2. REGISTER as contact for room URI

                                                    SUBSCRIBE to configuration
                                                    for users currently in rooms

                                                                                      room 815
Emergency calling as an LBS
   Existing emergency call systems (“911”) will no longer work in
    IP-based networks
        current 911 system uses outmoded operator trunk technology
   Emergency calling =
        call identification  sip:sos@domain or tel:112
        destination identification
             is this really an emergency call center?
        call routing to nearest emergency call center (ECC)
   Call routing is hardest
        must work internationally
        end system + network-based location determination
   Once solved:
        roadside emergency (AAA, ADAC, …)
        pizza emergency (nearest PizzaHut)
        but different privacy trade-offs  voluntary disclosure
Location-based call routing – UA
knows its location


INVITE sips:sos@

48° 49' N 2° 29' E

   proxy server

                     48° 49' N 2° 29' E  Paris fire department
Location-based call routing –
network knows location


            outbound proxy

                include location
                info in 302

      INVITE sips:sos@                        INVITE

      48° 49' N 2° 29' E
                                   map location to
                                   (SIP) domain
Service creation
    Tailor a shared infrastructure to individual users
    traditionally, only vendors (and sometimes carriers)
    learn from web models

                    programmer,      end user
    network         SIP servlets,    CPL
    servers         sip-cgi
    end system      VoiceXML         VoiceXML (voice),
Call Processing Language
   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
   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
CPL example
CPL example
<?xml version="1.0" ?>
<!DOCTYPE call SYSTEM "cpl.dtd">

    <lookup source="
        <proxy />
        <mail url="" />
CPL example: anonymous call
   <address-switch field="origin"
       <address is="anonymous">
          <reject status="reject"
          reason="I don't accept anonymous calls"
Service creation for presence
services (work-in-progress)
   Accept or deny subscriptions
   Shape presence notifications
       different level of detail for family, friends and
       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
Pushing context-sensitive data to
   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
   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
   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-