Multimedia SystemsNext-Generation Mobile - …hgs/papers/2000/harvard.pdf · $0.03 cable plant...

Mobile Multimedia 1

Next-Generation MobileMultimedia Systems

Henning SchulzrinneInternet Real-Time Lab

Dept. of Computer ScienceColumbia UniversityNew York, New York

http://www.cs.columbia.edu/[email protected]

Harvard University

November 27, 2000

Joint work with Elin Wedlund, the Telcordia ITSUMO and Home Control groups, andmembers of the IRT lab

November 2000

Mobile Multimedia 2

Overview

� Internet telephony

� next-generation wireless systems

� the Session Initiation Protocol (SIP)

� mobility modes and application-layer mobility

� mobile code

� signaling, inter-domain events and messaging

November 2000

Mobile Multimedia 3

What is Internet telephony

� = real-time communication using voice, video and other media across the Internetor private IP networks

� gateways to existing public phone network (PSTN)

� mostly PC to phone, but also between branch offices

� already 3.7 billion minutes for 2000 (out of about 200 billion)

� currently, about 3-10% of international traffic

� coming: PBX replacement

November 2000

Mobile Multimedia 4

Why Internet telephony?

� new services: web-style programming, integration with web, email, presence

� transport efficiency due to compression: 64 kb/s& 8 kb/s

� avoid local access charges, but already reduced 7c& 2.4c

� lower switching costs: $175/circuit& $0.03

� cable plant integration (PBX, DSL, cable modem)

� improved network management

� bypass international telephony settlement

November 2000

Mobile Multimedia 5

Internet Telephony Service Models

� Internet “PBX”

� Internet Centrex

� Internet Carrier

➠ same basic equipment, but size of gateway varies

November 2000

Mobile Multimedia 6

Internet PBX

1

IP

0 0

T1, ISDN (BRI/PRI) or analog lines

SIP proxy server

Ethernet

ISP

November 2000

Mobile Multimedia 7

IP centrex

Internet Heads Up Barber

IP

PSTNISP

Ralph’s Pretty Good Grocery

Chatterbox Cafe

November 2000

Mobile Multimedia 8

IP carrier

0 0

IP

1

MGCPH.248

SIP

SS7

GW

GW

GW

GWGW

GW

GW

GW

El Paso

San Francisco

Bell Canada

Montreal

Verizon

PacificBell

DallasQwest

MCI

BellSouth

New York

Chicago

PacificBell

Denver

BellSouth

LA

November 2000

Mobile Multimedia 9

Technical problems

� quality of service (mostly admission control, not scheduling)

� reliability

� set-up and control

� creating new services, modeling old services

� mobility support

November 2000

Mobile Multimedia 10

Third-Generation wireless

� goal: 144 kb/s moving, 384 kb/s stationary, 2 Mb/s indoors

� based on GSM or wideband CDMA

� implement IP(v6) in the hand set

� SIP as signaling system for voice calls in 3GPP

� in standardization now, deployment� 2003

November 2000


IETF VoIP protocol architecture

Signaling

TLSSCTP

IntServDiffServ

SLP

Directory/Discovery

master−slave

peer−to−peerRTSP

QoS Transport

SPIRITS

PINTLDAPDNS/enum TRIP

SIP MGCPH.248

RTP

Languages/APIsvoiceXMLCPL

servletssip−cgi

JAINParlay

November 2000


SIP overview

� protocol for establishing, modifying, tearing down (multimedia)sessions

� with registration to bind temporary locations to permanent names (e.g.,128.59.16.17 [email protected] )

� IETF Proposed Standard since March 1999

� multimedia = audio, video, shared applications, text, . . .

� also used for “click-to-dial” (PINT wg) and possibly Internet call waiting(SPIRITS wg)

� to be used for PacketCable Distributed Call Signaling and Third-GenerationWireless (3GPP, 3GPP2)

� proposed for presence, instant messaging and event notification

November 2000


SIP Components

entity does examples

proxy server forward calls firewall controller, “call router”

redirect server “application server”

user agent end system SIP phone, gateway, “softswitch”

registrar location mgt. mobility support

Roles are changeable, on a request-by-request basis

November 2000


SIP example: redirection

1

4

32

6

7

8

5

?

henn

ing

ACK [email protected]

INVITE [email protected]

302 Moved temporarily colu

mbi

a.ed

u

locationserver

columbia.edu

hgs

tu-berlin.de


200 OK

ACK [email protected]

ieee.org

Contact: [email protected]

November 2000


SIP example: proxying

10 media stream

4

[email protected]

8

7

1

[email protected]

9

6

5

3

?

henn

ing

hgs@

play

tune

play

cs.columbia.edu

200 OK

location server

ACK hgs@play

200 [email protected]

cs.tu-berlin.de INVITE hgs@play2

November 2000


SIP advanced features

� forking

� extensibility: new headers, methods, bodies

� security: web-like, PPP/CHAP or PGP

� multicast-capable

� support for personal, session, terminal, service mobility

� caller preferences: direct calls based on properties

November 2000


SIP forking proxies


[email protected]

INVITE bob@b

[email protected]

200 OK

INVITE carol@c

ACK

BYE [email protected]

200 OK

a.wonderland.com

macrosoft.com

CANCEL bob@c

November 2000


Mobility in an IP environment

Roaming users: logging in away from home network: hotel, home office

Terminal mobility: terminal moves between subnets

Personal mobility: different terminals, same address

Service mobility: keep same services while mobile

Session mobility: move active session between terminals

November 2000


Simple mobility: roaming users

� users visit other networks: laptop, PDA, hotel phone, . . .

� want to maintain external identity

� usually, just pass IP address to home registrar

� difficult if firewalls and NATs

– requests need to use local proxy

– thus, need to register locally

November 2000


Roaming Users – Dual Registration

Hotel California

DHCP

Contact: sip:eagles%[email protected]

REGISTER sip:home.com

To: [email protected]: [email protected]

Contact: sip:eagles%[email protected]

REGISTER sip:home.com

To: [email protected]: [email protected]

server

sip.hotelca.comREGISTER sip:sip.hotelca.com

home.comIP: 128.59.16.1

SIP: sip.hotelca.comDNS: hotelca.com

[email protected]

From: eagles%[email protected]: eagles%[email protected]

November 2000


Terminal mobility – mobile IP

CN

CH

HA

FAtunnelleddatadata

data

data

home network

foreignnetwork

mobile hostcorrespondent hostrouter with home agentfunctionalityrouter with foreign agentfunctionality

MH

CH

HA

HA

MH

MH

November 2000


Terminal mobility – mobile IP difficulties

� domain of IEEE 802.11 (link layer), 3GPP (radio access network), mobile IP(network layer), . . .

� network-layer mobility has problems:

– lack of deployment – home provider has no interest

– need two addresses – home and visiting

– dog-legged routing in IPv4

– may not work with IP address filtering except through triangle routing

– encapsulation overhead for voice: 8–20 bytes/packet for a 50-byte payload

– authentication of redirection

November 2000


SIP terminal mobility overview

� pre-call mobility➠ SIP proxy, redirect

� mid-call mobility ➠ SIP re-INVITE, RTP

� recovery from disconnection

November 2000


SIP terminal mobility: pre-call

� MH acquires IP address viaDHCP

� optional: MH finds SIP servervia multicastREGISTER

� MH updates home SIP server– deregister old, register new

� optimization: hierarchical LR(later)

CH

redir

3

1

2

5

foreignnetwork

homenetwork

4

mobile hostcorrespondent host

SIP redirect server

MH

CH

redir

3

1

2

5

4

SIP INVITE

SIP 302 moved temporarily

SIP INVITE

SIP OK

dataMH

MH

November 2000


SIP terminal mobility: mid-call

� MH!CH: new INVITE, withContact header and updatedSDP

� re-registers with home regis-trar

� requires one one-way delay

CH

13

2

foreignnetwork

homemobile hostcorrespondent host

SIP redirect server

MH

CH

redir

3

1

2

SIP INVITE

SIP OK

data

redir

network

MH

MH

MH

November 2000


SIP terminal mobility: multi-stage registration

Don’t want to bother home registrar with each move

Contact: alice@CAFrom: alice@NY

Contact: 193.1.1.1From: alice@NY

NY

REGISTERINVITE

Los Angeles

San Francisco

Contact: 192.1.2.3From: alice@NY

CA

1

3

2

4

registrarproxy

November 2000


Personal mobility

[email protected]:12015551234

[email protected]

tel:12128541111

[email protected]

[email protected]

[email protected]

[email protected]

(also used by [email protected])

yahoo.com

columbia.edu

November 2000


Personal mobility

� switch between PDA, cell phone, PC, Ethernet phone, Internet appliance, . . .

� several “generic” addresses, one person/function, many terminals

� e.g.,tel:2129397042 , [email protected] ,[email protected] or [email protected]

� SIP is designed for that – proxying and redirection does translation

� but: need mapping mechanisms to recognize registrations as belonging to thesame person

� some possible solutions:

– dip into LDAP personnel database or/etc/passwd to match phone numberand variations of name (J.Doe, John.Doe, Doe)

– need dialing plan to [email protected] andtel:2129397042 as same

November 2000


Service mobility

Examples:

� speed dial & address book

� media preferences

� special feature buttons (voice mail, do-not-disturb)

� incoming call handling instructions

� buddy lists

� features in home provider server

�! independent of terminal (including pay phone!), across providers

November 2000


Service mobility

� REGISTER can retrieve configuration information (e.g., speed dial settings,distinctive ringing or voice mail settings)

� but needs to be device-independent

� most such services (e.g., voicemail forwarding, call filtering) should remain onserver(s)

� use SIPRoute mechanism to direct path of outgoing calls via home server

Route: <sip:[email protected]>, <sip:[email protected]>

November 2000


Users creating services

� web: HTML�! ASP�! cgi, servlets

� Call Processing Language: similar role as HTML

– XML DTD flow graph for inbound & outbound calls

– generated by hand or graphical call flow editor

– can be imported back into editor

– could be generated by JavaScript, ASP

– safe: execution model, bounded timing (no loops)

– mobile code: uploaded viaREGISTER from terminal to call-handling proxy

– VoiceXML related, but for interactive voice response

November 2000


Example Call Processing Language script

<?xml version="1.0" ?><!DOCTYPE cpl SYSTEM "cpl.dtd">

<cpl><subaction id="voicemail">

<location url="sip:[email protected]">

<redirect /></location>

</subaction>

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

subfield="host"><address

subdomain-of="cs.columbia.edu"><location url=

"sip:[email protected]">

<proxy><busy>

<sub ref="voicemail" /></busy><noanswer>

<sub ref="voicemail" /></noanswer><failure>

<sub ref="voicemail" /></failure>

</proxy></location>

</address><otherwise>

<sub ref="voicemail" /></otherwise>

</address-switch></incoming>

</cpl>

November 2000


Programmable Internet Telephony

APIs servlets sip-cgi CPL

Language-independent no Java only yes own

Secure no mostly no, but can be yes

End user service creation no yes power users yes

GUI tools w/portability no no no yes

Call creation yes no no no

Multimedia some yes yes yes

Example: integration with iCal�! automatically export personal calendar to callhandling

November 2000


Service mobility – call handling

� need uniform basic service description model�! Call Processing Language(CPL)

� CPL for local call handling

� update CPL from terminal: add telemarketer to block list

� harder: synchronize CPL changes across multiple providers

� one possibility:REGISTER updates information, but device needs to know that ithas multiple identities

� merging of call logs

November 2000


SIP and mobility: issues

� doesn’t work for TCP applications – solutions:

– punt: “don’t type and drive”

– application-layer awareness: restart web, email, ftp transfer – need for deepfade anyway. . .

– TCP redirect (Snoeren/Balakrishnan)

– NAT-style boxes controlled by SIP (see Telcordia ITSUMO project)

� fast hand-off via SIP proxies with media translators

� but: works nicely for “vertical handoff” between different technologies - e.g.,transfer call from mobile handset to office videophone when arriving at work

November 2000


CINEMA: Columbia Internet Extensible Multimedia Architecture

request, responsetransactioncgi scriptsbasic authenticationdigest authentication

libsip

sipum

SIP UAcall stateREGISTERendpoint classSDP

siph323 sipconf

lipsip++

sipdrtspd

PGP

LDAP

SIP proxy server

libNT

SIP conferencing server

NT versions of aliases crypt

PGPPWLresparse

libdict

dictionary

hash tables

libmixer

hashtable inet regex getopt utilities

dstringhost2ip

mix RTP audio

SIP/RTSP unified messagingSIP/H.323 gateway

MySQLMySQL

SIP/MGCP gatewayRTSP media server

GSM, DVI codecs

msgflow

OpenH323 AT&T MGCP

CINEMA

sipgw

Xerces

config./DB access

libcine

parserURIsloggingMD5

software licensingTCPUDP

RTPlib

November 2000


Columbia Internet telephony components

sipum

RTSP

analogFXO

sipgw

sipgw

e*phone

sipd

sipconf

PC Linux/FreeBSD/NT

rtspd

sipc

MySQL

LDAP server

PhoneJack interface

RTPSIP

SIPRTP

T1/E1

PC NT

Sun Solaris

mediaRTSP

server

proxy/redirect server

SIP−H.323converter

unified

conferencingserver(MCU)

messagingserver

user database

sip−h323

November 2000


Scaling or how many calls can a SIP switch switch?

� 750,000 to 2.5 million busy hour call attempts for large class-5 switches =3.6 ms/call

� AT&T: 280 million calls a day = 0.3 ms/call

� Yahoo: 780 million page views/day

� AOL: 110 million emails/day

� AOL: 500 million IM/day

� web server: about 1,500 to 3,000 static requests/second

November 2000


Invisible Internet telephony

VoIP technology will appear in . . .

� Internet appliances

� home security cameras, web cams

� 3G mobile terminals

� fire alarms

� chat/IM tools

� interactive multiplayer games

November 2000


Commonalities between signaling and events

� presence is just a special case of events: “Alice just logged in”� “temperature inboiler exceeds300Æ F”

� need tolocatemobile end points

� may need to find several different destinations (“forking”)

� same addressing for users

� presence often precursor to calls

� likely to be found in same devices

� events already in VoIP: message alert, call events

November 2000


Events: SIP for Appliances

SUBSCRIBE [email protected]

NOTIFY [email protected]


DO [email protected] user agentSIP proxy

(RGW)

November 2000


Conclusion

� evolution from analog1960s

�! circuit-switched digital

20000s

�! packet-based

� uniform solution for wired and wireless multimedia terminals

� network-layer mobility neither sufficient nor available

� many common services don’t need network-layer support

� application-layer mobility for sessions

� one SIP-based approach for multimedia sessions, presence & events

November 2000

Multimedia SystemsNext-Generation Mobile - …hgs/papers/2000/harvard.pdf · $0.03 cable plant...

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