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SIP & H.323 Interworking

Name: Amir Zmora

Title: PM

Date: Feb 5 2003

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Agenda

The Need for Interworking

SIP – H.323 Interworking

Types of Implementations

Optional Co-Locations

Summary

References

The Need for Interworking

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A Bilingual VoIP World H.323

Large installation base

H.323 is still being developed and deployed

Enterprises are currently staying with H.323

SIP On carriers’ roadmap in addition to H.323

Softswitches mostly support SIP

3GPP has adopted SIP

Enhanced features (Presence, Instant Messaging)

The future of VoIP

SIP and H.323 will coexist for years to come therefore Interworking function (IWF) is required!

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Situational Analysis: VoIP Developers’ Protocol Support

Miercom Survey - 96 VoIP vendors responded worldwide (8/2001)

H.323 - 50%

SIP - 77%

MGCP - 36%

MEGACO - 53%

Plans to Add

Support

SIP – H.323 Interworking

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Open Issues

Synchronize with each protocol upgrade Resolve unmapped message scenarios Advanced call control handling Overlap sending Multiparty conferencing Media switching Handling SIP-H.323 security services QoS exchange between protocols– OSP ? Scalability– address resolution

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The VoIP Protocols

VoIP Protocols Provide: Signaling, Media Control and Media Streaming

Many similar components, but…

IP Layer

TCP/UDP IP

TPKT

Q.931 H.245 RAS RTCPRTP

Application Layer

Codecs

SIP SDP

Codecs

RTCP

RTP

Application Layer

H.323 SIP

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Main Mapped Functions Registration

Address Resolution

Call Control Call establishment and teardown

Supplementary Services

Out of band signaling (e.g. DTMF)

Media Control Capabilities exchange

Multimedia channel handling

Multipoint conferencing

Media Streams Transport

Other Add-On Services Presence, IM, etc.

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Interworking issues

Call establishment Getting more complex when H.323 is not using Fast

Start

Address mapping H.323 – Multiple addresses in alias list

Single address

Session description mapping SDP Vs H.245

More information on this can be found at end of presentation

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Basic Call Scenario H.323 to SIP

H.3

23 E

nd

poin

t

IWF

SIP

User

Ag

en

t

Setup(vipin@iwf.sip.com)

Alerting

Connect

RTP/RTCPCommon

protocol

H.245May be

included in Fast Start

INVITE

Ringing

OK

SDP Included in the

INVITE

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Basic Call Scenario SIP to H.323

H.3

23 E

nd

poin

t

IWF

SIP

User

Ag

en

t

Setup(vipin@iwf.sip.com) INVITE

Ringing

Alerting

OK

Connect

RTP/RTCPCommon protocol

H.245 May be

included in Fast Start

SDP Included in the

INVITE

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Class 5 Features Mapping

H.323 and SIP address supplementary services differently H.323 defines each feature specifically SIP provides building blocks and call flows

H.323 Call Transfer Call Diversion/Forwarding Call Hold Call Park and Pickup Call Waiting Message Waiting Name Identification Call Completion on Busy Call Offer Call Intrusion

SIP Call Transfer Call Forwarding Third-Party call control Call Hold, Music on Hold

Single line extension Incoming Call Screening Outgoing Call Screening Find-Me Call Park & Pickup Automatic Redial

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Multiparty Conferencing

H.323Terminal

MCU

H.323 Centralized/Decentralized Conferences

SGW

SIP Terminal

SGW

H.323Terminal

H.323Cloud

SIP Full Meshed Conference

SGW

SIP Terminal

H.323Terminal

SIP Terminal

SIP Terminal

SIP Terminal

H.323Terminal

SIPCloud

Types of Implementations

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Gateway Types

Softswitch at the ITSP Edge

Signaling Gateway at the ITSP Edge

Signaling Gateway at the Enterprise Network Edge

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Softswitch at the ITSP Edge

ITSP

IP Network

Enterprise

Gatekeeper

Softswitch

SCN

Gateway

Gateway

H.323 SIP

Enterprise

Proxy Server

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At the network edge

Focuses on bridging IP and PSTN

Delivers mostly add-on services

Very complex

Must be carrier-grade High capacity Highly redundant

Expensive!

Softswitch at the ITSP Edge

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Signaling Gateway at the ITSP Edge

SCN

ITSP

IP Network

EnterpriseH.323

Gatekeeper

Softswitch

Gateway

Gateway

SIP

SIP Proxy

SIP

H.323

Signaling Gateway

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On the network edge

Focuses on “simple” H.323-SIP bridging

No add-on services

Simple functionality

Must be carrier-grade High capacity Highly redundant

Relatively inexpensive

Signaling Gateway on the ITSP Edge

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Signaling Gateway on the Enterprise Network Edge

ITSP

IP Network

Enterprise

Proxy

Softswitch

SCN

Gateway

Gateway

SIP

GatewaySIP

Signaling Gateway

Gatekeeper

SIP Proxy

SIP

SIP

H.323

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At the network edge

Focus on “simple” H.323-SIP bridging

No add-on services

Simple functionality

Does not need to be carrier grade

Inexpensive

Signaling Gateway at the Enterprise Network Edge

Address Resolution

Optional Co-Locations

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Within SIP Proxy

SIP Calls Register with SIP

Proxy SIP Proxy forwards

UA Registrations to Gatekeeper via SG

H.323 Calls Regular RAS scenario

SIP - H.323Signaling Gateway

REG SIP Proxy/ Registrar

SIP UA H.323 Terminal

Gatekeeper

RRQRRQ

LRQ

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SIP - H.323Signaling Gateway

REGGatekeeperSIP UA H.323

TerminalRRQ

SIP Proxy/ Registrar

REG

H.323 Calls RAS Forward to proper

SIP Registrar/Proxy

SIP Calls Similar to regular SIP

Calls

Within Gatekeeper

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As An Independent Entity

SIP Calls Register with SIP Proxy When call reaches the

signaling gateway it queries the H.323 network

H.323 Calls Register with

Gatekeeper When call reaches the

signaling gateway it queries the SIP network

SIP - H.323Signaling Gateway

REGSIP UA H.323

Terminal

SIP Proxy/ Registrar

REG

GatekeeperRRQ

RRQ

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All-In-One

SIP - H.323Signaling Gateway

REGSIP UA H.323

TerminalSIP Proxy/ Registrar Gatekeeper

RRQ

SIP Calls Register with SIP

Proxy

H.323 Calls Register with

Gatekeeper

Signaling Gateway Use both for address

resolution

Conclusion

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Summary

We are in a multi-protocol world therefore both SIP and H.323 should be supported

Increased complexity of H.323 and SIP create

interworking and interoperability challenges

Advanced call services – complex/open issue

References

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References of Interworking Standards

IETF SIP-H.323 Interworking draft “draft-agrawal-sip-h323-interworking-reqs-03.txt”

Links: www.radvision.com

www.h323forum.org

www.sipforum.org

My mail: amirz@radvision.com

Interworking Issues

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Call Establishment

SIP INVITE / H.323 Fast Start Signaling Destination Address

Local and Remote Media Capabilities

Local and Remote Media Addresses

Regular H.323 Setup Stage-1: Signaling Destination Address

Stage-2: Local and Remote Media Capabilities

Stage-3: Local and Remote Media Addresses

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Address Mapping Issues - 1

H.323 uses several ASN.1 fields while SIP uses URI only SIP URI to H.323 address is simple

H.323 address to SIP might be complicated

Address Translation Example SIP To H.323

“sip:+1-201-529-1212:1234@bridge.com;user=phone”

Mapped in H.323 to->H.323 Address: {

e164 = "12015291212",

h323-ID = "sip:+1-201-529-1212:1234@bridge.com",

url-ID = "sip:+1-201-529-1212:1234@bridge.com",

email-ID= "+1-201-529-1212:1234@bridge.com"

}

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Address Mapping Issues - 2

H.323 to SIP Address Translation Example

H.323 E164: “12015291212” “sip:+1-201-529-1212@host;user=phone”

H.323 H323Id: “mailto:user@domain” “sip:user@domain”

SIP and H.323 ENUM Support Phone# 480-990-1101 URL

“1.0.1.1.0.9.9.0.8.4.e164.arpa”

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Session Description Mapping - 1

H.245 Very comprehensive protocol

Covers many control issues (e.g. Chair Control)

SDP Is a media description language

Relatively limited

Lack of cross-media, inter-media constraints

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Session Description Mapping - 2

Mapping SDP to H.245

SDP message can easily be mapped to H.245

Straightforward

H.245 to SDP

H.245 message to one or more SDP messages

Can be complicated or impossible under certain circumstances

www.radvision.com

amirz@radvision.com

Thank You