Transcript Interworking Between SIP/SDP and H.323
Interworking Between SIP/SDP and H.323
Kundan N. Singh, Dept. of Computer Science, Columbia University [email protected]
Agenda • Compare SIP/H.323
• Problems in interworking • Possible solutions • Conclusion • Q/A Jan 25, 2000 Kundan Singh/SIP-H.323
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Q931 H245 RTP RAS H450 H323 Box Jan 25, 2000
What is H.323 ?
Multimedia Communication Protocol Terminal/ User Agent Gatekeeper Terminal/ User Agent MCU (Conferencing) Gateway (Bridge to another network) H323 Network Kundan Singh/SIP-H.323
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What is SIP ?
Session Initiation Protocol for Internet Servers Registrar Redirect Proxy UserAgent UAS/UAC Jan 25, 2000 Kundan Singh/SIP-H.323
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H.323 vs SIP
Typical UserAgent Protocol stack for Internet Terminal Control/Devices Q.931
H.245
RAS RTCP Codecs RTP TPKT TCP UDP IP and lower layers Terminal Control/Devices SIP SDP Codecs RTCP RTP Transport Layer Jan 25, 2000 Kundan Singh/SIP-H.323
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SIP vs H.323
• Text based request response • SDP (media types and media transport address) • Server roles: registrar, proxy, redirect • Binary ASN.1 PER encoding • Sub-protocols: H.245, H.225 (Q.931, RAS, RTP/RTCP), H.450.x...
• H.323 Gatekeeper
Both use RTP/RTCP over UDP/IP
Jan 25, 2000 Kundan Singh/SIP-H.323
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H.323
Interworking Problems
Call setup translation SIP Q.931 SETUP Q.931 CONNECT Terminal Capabilities Terminal Capabilities Open Logical Channel Open Logical Channel Destination address ([email protected]) Media capabilities (audio/video) Media transport address (RTP/RTCP receive) INVITE 200 OK ACK • Multi-stage dialing • H.323v2 Fast-start is optional Jan 25, 2000 Kundan Singh/SIP-H.323
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H.323
Interworking Problems
User Registration ?
H.323 Gatekeeper SIP registrar SIP H.323 terminal Alias: Henry E164: 7040 SIP user agent sip:[email protected]
• Location independent user identifier ?
• Use information from both networks Jan 25, 2000 Kundan Singh/SIP-H.323
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Interworking Problems
Media Description SIP/SDP (dynamically choose from listed modes) List of alternative set of algorithms.
audio G.711 Mu law, G.723.1, G.728
video H.261 H.323/H.245 (declare your exact modes) Supports inter-media constraints { [G.711 Mu law, G.711 A law][H.261 video]} { [G.723.1] [no video] } • Translation in both directions • Algorithm selection by end-systems Jan 25, 2000 Kundan Singh/SIP-H.323
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Interworking Problems
Call Services • H.323 Conferencing: centralized signaling control, MC (Multi point Controller) • Supplementary services, like call transfer: H.450.x
• SIP Conferencing: centralized bridged + decentralized distributed • REFER, 3pcc Jan 25, 2000 Kundan Singh/SIP-H.323
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Interworking Problems
Security and QoS • H.323 uses H.235, whereas SIP uses Basic, Digest, PGP • Media Traffic end-to-end; QoS ?
Jan 25, 2000 Kundan Singh/SIP-H.323
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What we want ?
• Transparent translation • Minimum modification in SIP or H.323
• Use features from both SIP and H.323
• Direct RTP/RTCP traffic; end-to-end Jan 25, 2000 Kundan Singh/SIP-H.323
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User registration
Registration info
to
foreign network H.323 terminal 128.59.19.200
REGISTER [email protected]
Contact:pc1 H.323 Gatekeeper + SGW pc1.office.com
home.com
SIP registrar server INVITE [email protected]
Contact:128.59.19.200
3xx Moved Contact:pc1 SIP user agent [email protected]
use SIP REGISTER and/or H.323 RRQ/RCF Jan 25, 2000 Kundan Singh/SIP-H.323
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User registration
Registration info
from
foreign network H.323 terminal 128.59.19.200
H.323 Gatekeeper pc1.office.com
Contact:128.59.19.200
LRQ/LCF home.com
SIP registrar server + SGW INVITE [email protected]
200 OK SIP user agent [email protected]
use SIP OPTIONS and/or H.323 LRQ/LCF Jan 25, 2000 Kundan Singh/SIP-H.323
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User registration
Different Architectures • SGW co-located with H.323 gatekeeper • SGW co-located with SIP registrar/proxy server • Independent SGW Jan 25, 2000 Kundan Singh/SIP-H.323
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Call Setup
with H.323v2 Fast Start (Almost) One-to-one mapping between SIP and H.323 messages.
H323 Setup/FastStart SIP INVITE Connect/FastStart 200 OK.
ACK RTP/RTCP Reverse direction is similar Kundan Singh/SIP-H.323
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Call Setup
without Fast Start H.323
Q.931 SETUP Q.931 CONNECT Terminal Capabilities Terminal Capabilities Open Logical Channel Open Logical Channel Destination address ([email protected]) Media capabilities (audio/video) Media transport address (RTP/RTCP receive) SIP INVITE 200 OK ACK
Accept the call from H.323, forward to SIP after OLC ? Not desirable.
Jan 25, 2000 Kundan Singh/SIP-H.323
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Call Setup
without Fast Start, SIP to H.323
H323 Setup/Q931 INVITE Connect/Q931 Signaling Gateway Capabilities/H245 Capabilities/H245.
Open Logical Channel/ H245 Acknowledgement Open Logical Channel / H245 Acknowledgement Media Transport Address 200 OK.
ACK RTP/RTCP Jan 25, 2000 Kundan Singh/SIP-H.323
SIP 17
Call Setup
without Fast Start, H.323 to SIP H323 Setup/Q931 Connect/Q931 Capability Exchange Open Logical Channel Acknowledgement Open Logical Channel Acknowledgement Signaling Gateway Media Transport Address INVITE 200 OK ACK Re-INVITE/SIP+SDP RTP/RTCP SIP Jan 25, 2000 Kundan Singh/SIP-H.323
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Media Capability
• Modify SIP/SDP : multiple capability sets, or...
• Let the SGW choose a sub-set of capabilities for SIP side • Re-INVITE or change in H.323 mode or logical channels, whenever it changes Jan 25, 2000 Kundan Singh/SIP-H.323
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Conclusion
What can be done ? What can’t ?
• Basic audio/video call • Transparency of User registration • Advanced calls with complex sessions • Conferencing • SIP centered, H.323 centered • Other supplementary services • . . .
Jan 25, 2000 Kundan Singh/SIP-H.323
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Conclusion
Status • IETF mailing list “[email protected]”. Finalizing requirements document • IMTC and ETSI TIPHON • Convergence between SIP and H.323 in newer versions Jan 25, 2000 Kundan Singh/SIP-H.323
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Conclusion
Implementation -
sip323
• Prototype (free download) system at http://www.cs.columbia.edu/~kns10/software/sip323 •Other information at http://www.cs.columbia.edu/~kns10/research/gw • My contact info: [email protected]
Jan 25, 2000 Kundan Singh/SIP-H.323
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