IRT Lab IP Telephony Deployment @ Columbia

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IP Telephony Deployment @ IP Telephony Deployment @ ColumbiaColumbia

Henning SchulzrinneWenyu Jiang

Sankaran NarayananXiaotao Wu

Columbia UniversityDepartment of Computer Science

{hgs,wenyu,sankaran,xiaotaow}@cs.columbia.edu

IRT Lab IP Telephony Deployment @ Columbia

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IP Telephony and ProtocolsIP Telephony and Protocols

External line7040

7042PBX

Corporate/Campus

InternetLAN

8154

8151

8152

8153

PBX

Another campus

LAN

IP Phone Client/ Audio over RTP

VoIP Gateway VoIP Gateway

home.com

office.com

SIP server

SIP server

Call “bob@office.com”

IRT Lab IP Telephony Deployment @ Columbia

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ArchitectureArchitecture

SIP proxy,redirectserver

SQLdatabase

sipd

SIPH.323convertor

NetMeetingsip323

H.323

rtspd

SIP/RTSPUnified

messaging

RTSP media server

sipum

Quicktime

RTSP clients

RTSP

SIP conference

server

sipconf

T1/E1 RTP/SIP

Telephone

Cisco 2600 gateway

Telephoneswitch

Web based configuration

Web server

Cisco 7960

3Com

e*phone

sipc

Software SIP user agents

Hardware Internet (SIP)

phones

Pingtel

SNMP

IRT Lab IP Telephony Deployment @ Columbia

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CINEMA: Columbia InterNet CINEMA: Columbia InterNet Extensible Multimedia ArchitectureExtensible Multimedia Architecture

• Web interface– Administration– User configuration

• Unified Messaging

– Notify by email

– rtsp or http

• Portal Mode– 3rd party IpTelSP

IRT Lab IP Telephony Deployment @ Columbia

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PSTN-IP Inter-OperationPSTN-IP Inter-Operation

PBXPSTN

External T1/CAS

Regular phone(internal)

Call 93971341

SIP server

sipd

Ethernet

3

SQLdatabase

4 7134 => bob

sipc

5

Bob’s phone

• Outgoing calls are similar

GatewayInternal T1/CAS(Ext:7130-7139)

Call 71342

5551212

IRT Lab IP Telephony Deployment @ Columbia

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Servi ce

External

Medi a

Appl i cati on

SI P proxy server

SI P phone

si pc

RAT

WB

VI C

CHAT

VNC

si pc

RAT

WB

VI C

CHAT

VNC

audi o

SI P si gnal

audi o

vi deo

whi te board

text

desktop shari ng

SI P for presenceSI P i nstance messagi ng

SI Pdevi cecontrol

CPL scri pt

Devi ce gateway

SI P CGIengi ne

CPL engi ne

CGI scri pt

CGI i nterface

servi ce i nterfaceSI P si gnal

http: / /mai l to:

SI P cal l setupSI P cal l transfer

sipc – A SIP User Agentsipc – A SIP User Agent

IRT Lab IP Telephony Deployment @ Columbia

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Controller

SIP Stack

Transmission

Controller

SIP Stack

Transmission

Service LogicExecution

Environment

CPLscript

CGIscript

ServiceCreation

Environment

Service LogicExecution

Environment

CPLscript

CGI script

ServiceCreation

Environment

GUI GUI

Media transmission

Mediaapplication

Mediaapplication

sipc Architecturesipc Architecture

IRT Lab IP Telephony Deployment @ Columbia

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What about Audio Quality? What about Audio Quality?

• Voice Codec: G.711 = toll quality at 64 kb/s• Bandwidth: rarely an issue on campus networks

with Gigabit core switches• Measurement in the Columbia intranet (campus-

wide), over a total of 24 hours– Average (one-way) delay < 1ms

– Jitter: packets > 10ms = 0.003%-0.05%

– Loss: 0.001%-0.01%, 0.005% average

• Using Ethernet switches instead of hubs prevents excessive delay/jitter.

IRT Lab IP Telephony Deployment @ Columbia

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Scalability, Security and OtherScalability, Security and Other

• Scalability based on multiple servers:– SIP Server, via DNS SRV– Gateway and LAN bandwidth– Media servers (voice-mail and conferencing)

• Security:– Authenticate users; Disallow auth-bypass.– Gateway calls for only authorized users.

• Further issues of study:– Service availability/reliability, QoS– Privacy/encryption, Electronic Billing