Ubiquitous SIPUbiquitous SIP

Henning Schulzrinne(with Stefan Berger, Stelios Sidiroglou, Kundan Singh, Xiaotao Wu, Weibin Zhao and the RPIDS

authors)Columbia University IRT Lab

Hewlett Packard – March 2003

OverviewOverview

What is ubiquitous computing? Core ubiquitous communications

functionality Brief introduction to SIP Ubiquitous computing in SIP and

SLP On-going work at Columbia

What is ubiquitous What is ubiquitous computing?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 Ubiquitous computing aspectsaspects 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

Components of ubiquitous Components of ubiquitous communicationscommunications

Service discovery discover devices

Service mobility configuration information moves to new devices

Event notification for context awareness

Context-awareness location, user actions, location properties, …

Example “ubicomp” Example “ubicomp” projectsprojects 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

Ubiquitous computing using Ubiquitous computing using SIP – what’s different?SIP – what’s 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

What is SIP?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 Microsoft’s Windows Messenger (4.7)

includes SIP

Basic SIP message flowBasic SIP message flow

SIP trapezoidSIP trapezoid

SIP trapezoid

outbound proxy

a@foo.com: 128.59.16.1

registrar

SIP event notificationSIP 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 sip:alice@vmail.example.com SIP/2.0To: <sip:alice@example.com>From: <sip:alice@example.com>;tag=78923Call-Id: 1349882@alice-phone.example.comContact: <sip:alice@alice-phone.example.com>

NOTIFY sip:alice@alice-phone.example.com SIP/2.0…Event: message-summarySubscription-State: active

Messages-Waiting: yesMessage-Account: sip:alice@vmail.example.comVoice-Message: 2/8 (0/2)

SIP event architectureSIP 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@hp.com”)

SIP presence architectureSIP presence architecture

PA

a@foo.com: 128.59.16.1

watcher

PUAs

Alice Bob

PUBLISH

REGISTERSUBSCRIBE

NOTIFY

<?xml version="1.0" encoding="UTF-8"?><p:presence xmlns:p="urn:…" entity="pres:alice@example.com"><p:tuple id="sg89ae"> <p:status> <p:basic>open</p:basic> </p:status> <p:contact>tel:09012345678</p:contact></p:tuple></p:presence>

Session mobilitySession 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

Session mobility via 3PCCSession mobility via 3PCC

INVITE speakerphonem=audioc=pc42

INVITE displaym=videoc=pc42

192.0.2.1

192.0.2.7

INVITE pc42m=videoc=192.0.2.7m=audioc=192.0.2.1

pc42

How to find services?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?type=printer

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 Service Location Protocol (SLP)(SLP)

Version 2 standardized June 1999

UA

DA

SA

SA

SrvReg

SrvRply

SrvRqst

SrvRqst SrvReg

DAAdvert

SLP attribute exampleSLP attribute exampleURL service:printer:lpr://igore.wco.ftp.com/draft

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-size=na-letter),(resolution=res-600),x-OK

Other service location Other service location mechanismmechanism DNS SRV/NAPTR DNS TXT records (Apple Rendezvous) DNS-SD UPnP uses SSDP:

multicast HTTP over UDP

M-SEARCH * HTTP/1.1S: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6Host: 239.255.255.250:reservedSSDPportMan: "ssdp:discover“ST: ge:fridgeMX: 3

HTTP/1.1 200 OKS: uuid:ijklmnop-7dec-11d0-a765-00a0c91e6bf6Ext: Cache-Control: no-cache="Ext", max-age = 5000ST: ge:fridgeUSN: uuid:abcdefgh-7dec-11d0-a765-00a0c91e6bf6AL: <blender:ixl><http://foo/bar>

Service mobilityService 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

LocationsLocations 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”

Determining locationsDetermining 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

DHCP for locationsDHCP for locations modified dhcpd (ISC) to generate location information use MAC address backtracing to get location information

DHCPserver

458/17 Rm. 815458/18 Rm. 816

DHCP answer:sta=DC loc=Rm815lat=38.89868 long=77.03723

8:0:20:ab:d5:d

CDP + SNMP8:0:20:ab:d5:d 458/17

Determining locationsDetermining locations For many devices,

can’t 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

DHCP for locationsDHCP 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)

Location-based servicesLocation-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”

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

SIP extensions for location-SIP extensions for location-based servicesbased 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

RPIDS: rich presence dataRPIDS: 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

PA

watcher

PUA watcher

watcher

PUBLISH

NOTIFY

everything

"vague"

CPL

INVITE

Aside: SIP caller Aside: SIP caller preferencespreferences

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

Aside: SIP caller Aside: SIP caller preferencespreferences 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”

a@foo.com: 128.59.16.1

sip:isabel@a.com;languages="es"sip:isabel@a.com;languages="en";q=0.2

sip:bob@a.com;languages="en"

INVITE sip:sales@a.comAccept-Contact: *;languages="en"

INVITE

REGISTER

RPIDS: Rich presence data RPIDS: Rich presence data Integrates caller preferences information into

presence announcements <class>: presentity, group, device <category>: 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 <from>, <until>: status validity <activity>, <idlesince>: activity for device <relationship>: family, associate, assistant,

supervisor <label>: permanent label, not to be modified

RPIDS exampleRPIDS example<tuple id="7c8dqui"> <status> <basic>open</basic> <contact>sip:secretary@example.com</contact> <cap:capabilities>

<cap:feature name="Media"> <cap:value>voice</cap:value> <cap:value negated="true">message</cap:value> </cap:feature> </cap:capabilities> </status> <ep:relationship>assistant</ep:relationship> <note>My secretary</note></tuple>

Event filteringEvent 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 languageLocation 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 > threshold entering or leaving certain area entering or leaving category or behavioral type

Columbia SIP servers Columbia SIP servers (CINEMA)(CINEMA)

InternalTelephoneExtn: 7040

SIP/PSTN Gateway

Department PBX

Web based configuration

Web server

Telephoneswitch

SQLdatabase

sipd:Proxy, redirect, registrar server

Extn: 7134

xiaotaow@cs NetMeeting

H.323

rtspd: media server

sipum: Unified messaging

Quicktime

RTSP clients

RTSP

Extn: 7136

713x

Single machine

SNMP(Network Management)

sipconf: Conference server

siph323: SIP-H.323 translator

Local/long distance1-212-5551212

Location-based services in Location-based services in CINEMACINEMA 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)

CINEMA systemCINEMA system

All-SIP implementationAll-SIP implementation

Service creationService creation

programmer, carrier

end user

network servers

SIP servlets, sip-cgi

CPL

end system VoiceXML VoiceXML (voice),LESS

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

sip-cgisip-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 (?

arg1=var1&arg2=var2) 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

sip-cgi examplessip-cgi examples Block *@vinylsiding.com:if (defined $ENV{SIP_FROM} && $ENV{SIP_FROM} =~

"sip:*@vinylsiding.com") { print "SIP/2.0 600 I can't talk right now\n\n";}

Make calls from boss urgent:if (defined $ENV{SIP_FROM} && $ENV{SIP_FROM}

=~ /sip:boss@mycompany.com/) { foreach $reg (get_regs()) { print "CGI-PROXY-REQUEST $reg SIP/2.0\n"; print "Priority: urgent\n\n"; }}

Call Processing Language Call Processing Language (CPL)(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

CPLCPL 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 exampleCPL example

String-switchfield: from

match:*@example.com

otherwise

proxytimeout: 10s

locationurl: sip:jones@

example.comvoicemail.

merge: clear

locationurl: sip:jones@

example.com

redirect

Call

busy

timeout

failure

CPL exampleCPL example<?xml version="1.0" ?><!DOCTYPE call SYSTEM "cpl.dtd">

<cpl> <incoming> <lookup source="http://www.example.com/cgi-bin/locate.cgi?

user=jones" timeout="8"> <success> <proxy /> </success> <failure> <mail url="mailto:jones@example.com&Subject=lookup%20failed" /> </failure> </lookup> </incoming></cpl>

CPL example: anonymous CPL example: anonymous call screeningcall screening<cpl>

<incoming><address-switch field="origin"

subfield="user"><address is="anonymous">

<reject status="reject"reason="I don't accept anonymous

calls" /></address>

</address-switch></incoming>

</cpl>

Service creation – a Service creation – a comparisoncomparison

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

Service creation for presence Service creation for presence services (work-in-progress)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

Pushing context-sensitive Pushing context-sensitive data to usersdata 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

ConclusionConclusion 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