H.323 Overview
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![Page 1: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/1.jpg)
H.323 Overview
Demystifying Multimedia Conferencing Over the Internet
Using the H.323 Set of Standards
![Page 2: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/2.jpg)
Numbers to know:
• H.225 - call setup, establishment, tear-down
• H.245 - media capability negotiation
• H.261 & H.263 - video codecs
• G.7xx - audio codecs
![Page 3: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/3.jpg)
H.323 Architecture
Audio and Video codecs
H.225 Layer
H.245 Q.931 RASAudio and Video I/O
![Page 4: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/4.jpg)
How does all this work?
( the signaling example )
![Page 5: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/5.jpg)
How does all this work?
Calling party opens H.323 client
![Page 6: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/6.jpg)
How does all this work?
Q.931 Setup
Setup
![Page 7: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/7.jpg)
How does all this work?
Q.931 Alerting (ringing)
Alerting
![Page 8: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/8.jpg)
How does all this work?
Q.931 Connect
Connect
![Page 9: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/9.jpg)
How does all this work?
H.245 terminal capabilities
termCapSet
![Page 10: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/10.jpg)
How does all this work?
H.245 terminal capabilities
termCapAck
![Page 11: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/11.jpg)
How does all this work?
H.245 determine Master/Slave
mSDet
![Page 12: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/12.jpg)
How does all this work?
H.245 determine Master/Slave
mSDetAck
![Page 13: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/13.jpg)
How does all this work?
H.245 determine Master/Slave
mSDetConfirm
![Page 14: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/14.jpg)
How does all this work?
H.245 open channel (RTP)
openReq
![Page 15: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/15.jpg)
How does all this work?
H.245 open channel (RTP)
openAck
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How does all this work?
RTP connection
connected
![Page 17: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/17.jpg)
How does all this work?
H.245 End Session
endSession
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How does all this work?
Q.931 Release Complete
ReleaseComplete
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Gatekeeper
• Purpose is to manage resources in a zone
• Uses RAS signaling
• Provides address resolution
• Alias Address Modification
• Approves calls based on bandwidth
• Dialed Digit Translation (PSTN)
• Directory Services
![Page 20: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/20.jpg)
Advanced Features
• Interoperability with PSTN
• Centralized, decentralized, and hybrid multicast conferences through MCU
• Datastream and multicast encryption (H.235)
• Cascading MC’s for large conferences
• FastStart connection (similar to SIP)
![Page 21: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/21.jpg)
H.323 Issues
• Interoperability issues between clients
• Massive, monolithic, closed specification
• Not designed to be readily extensible
• Competition from simpler, open, IETF standards (SIP, SDP, RTP)
![Page 22: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/22.jpg)
Why is this important?
• Stress test of real latency sensitive data
• H.323 central to QoS issues
• Authentication carried out through CiNIC?
![Page 23: H.323 Overview](https://reader035.fdocuments.us/reader035/viewer/2022062517/56813675550346895d9e011a/html5/thumbnails/23.jpg)