1 sip & h.323 interworking name: amir zmora title: pm date: feb 5 2003
TRANSCRIPT
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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([email protected])
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([email protected]) 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: [email protected]
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:[email protected];user=phone”
Mapped in H.323 to->H.323 Address: {
e164 = "12015291212",
h323-ID = "sip:+1-201-529-1212:[email protected]",
url-ID = "sip:+1-201-529-1212:[email protected]",
email-ID= "+1-201-529-1212:[email protected]"
}
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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
