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K. Stoeckigt, Secure real-time audio/video communication – H.350, Encryption & Gatekeeper/Proxy – using H.323 (…and a bit SIP) Tutorial/workshop.

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Presentation on theme: "K. Stoeckigt, Secure real-time audio/video communication – H.350, Encryption & Gatekeeper/Proxy – using H.323 (…and a bit SIP) Tutorial/workshop."— Presentation transcript:

1 K. Stoeckigt, Secure real-time audio/video communication – H.350, Encryption & Gatekeeper/Proxy – using H.323 (…and a bit SIP) Tutorial/workshop session - Introduction to VC technology and H th APAN Meeting Bangkok, Thailand January 2005

2 K. Stoeckigt, Outline What is videoconferencing and why should you use it? –motivating example –H.323 around the world H.323 – The standard A recipe for successful H.323 videoconferencing

3 K. Stoeckigt, What is videoconferencing and why should you use it? A motivating example –Videoconferencing comes in all sorts of flavors, colors, languages, and and and…. Canadian StyleHungarianDutchMcD or US flavor JapaneseAustralian Style German Slovenian

4 K. Stoeckigt, What is videoconferencing and why should you use it? What standards are available right now? –Several!! H.323 (VC over IP) –mostly used for videoconferencing H.320 (VC over ISDN) – still widely used; good as backup option SIP – show up on Stephens and Quincys Workshop tomorrow –mostly used for IP telephony AccessGrid – next door –High bandwidth, multicast applications other MBone tools –Since this workshop is dealing with H.323, we are just talking about H.323…ok…a bit SIP will be in at the end

5 K. Stoeckigt, What is videoconferencing and why should you use it? Videoconferencing is IP telephony with pictures A better definition Point-to-point or multipoint? –a point-to-point connection only includes two participating sides, whereas multipoint can connect n-many participating sides A videoconference is a virtual meeting of two or more participants (single persons, groups) at different locations who communicate in real-time via a bidirectional audio/video link. Digital audio, video and text can be shared (and edited) between the participants. Point-to-pointMultipoint

6 K. Stoeckigt, What is videoconferencing and why should you use it? VC is a modern communication medium It can support –Education, e.g. K-12, Universities, etc. Guest lectures can give talks without traveling No need to skip lectures if the lecturer is away Inter-cultural experience, e.g. in language classes with other countries Best example for this scenario: Megaconference Jr. –Collaborative work/research Work/research with other people/groups in other countries/at different locations –e.g. group meetings, etc. –Students use of modern technology connection to the rest of the world…maybe a connection home for international students –Many more scenarios….

7 K. Stoeckigt, What is videoconferencing and why should you use it? Does it work, and H.323 around the world? –YES IT DOES –Megaconference - Annual worlds largest videoconference Initiated by Dr. Bob, OSU Last years event (December 2004): –372 participation sites around the world –All continents, except Antarctica –Many Screenshots at –Streams on the web page

8 K. Stoeckigt, What is videoconferencing and why you should use it? H.323 around the world –Cascaded MCUs of last years event (picture on the right) –What else? Vide, but Egon will talk about Vide a bit later todayhttp://www.vide.net –As you can see, H.323 is widely used, so you should use it too

9 K. Stoeckigt, H.323 – The standard H.323 is an ITU standard, first introduced in 1996 It is an umbrella standard, covering some of the following standards –H –H.245 –H.235 –…. Current version in V.5 (most systems however still use V.4) –Draft versions of the standard can be downloaded at The H.323 standard describes terminals and other entities that provide multimedia communication services over packet based networks (PBN). H.323 does not guarantee Quality of service.

10 K. Stoeckigt, H.323 – The standard Requires –Video H.261 (CIF (352x288), QCIF (176x144)) –Audio G.711 (~ Telephone quality) –Data formats H.225 (Call signaling) H.245 (Control protocol) Options –Video H.263, H.263+, H.264,… –Audio G.722,… –Data T.120 Now you know why its called umbrella standard

11 K. Stoeckigt, H.323 – The standard Entities of H.323 are: –Terminals (I will refer to it as endpoint(s)) Terminals are a voice/video endpoint, such as an IP-Phone, a videoconferencing system (Viavideo, Netmeeting®, other systems) Terminal has to support the mandatory requirements –MCUs Multipoint Conference Units commonly used if more than 2 participants want to conference with each other MCU consist of two parts –Multipoint controller (MC): controls the call signaling –Multipoint processor (MP): responsile for media handling, such as switching, synchronization, etc.

12 K. Stoeckigt, H.323 – The standard Entities of H.323 are: –Gateways Bridging to other communication networks such as the ISDN world, OPBTPS (old plain boring telephone system) –Gatekeepers Address translation (Which IP is ?) Call control Bandwidth control Zone control Admission control

13 K. Stoeckigt, H.323 – The standard Explains several different call scenarios –Endpoint Endpoint –Endpoint GK direct Endpoint –Endpoint GK routed Endpoint –Endpoint GK {direct|routed} GK {direct|routed} Endpoint –several other scenarios Four examples should demonstrate how H.323 partners communicate with each other –Endpoint Endpoint (communication without Gatekeeper) –Endpoint GK direct Endpoint (communication using a Gatekeeper) –Endpoint GK routed Endpoint (communication using a Gatekeeper in routed mode) –Endpoint GK proxy Endpoint (communication using a Gatekeeper/Proxy (this is not specified in the H.323 standard))

14 K. Stoeckigt, H.323 – The standard ARQ: Admission request ACF: Admission confirm ARJ: Admission reject RRQ: Registration request RCF: Registration confirm RRJ: Registration reject DRQ: Disengage request DCF: Disengage confirm DRJ: Disengage reject BRQ: Bandwidth request BCF: Bandwidth confirm BRJ: Bandwidth reject All the messages are also called RAS message (Registration Admission Status) Useful abbreviations for the next few slides

15 K. Stoeckigt, H.323 – The standard Endpoint Endpoint (Three phases) –Phase 1: Call connect A sends B a setup request If B accepts the request a connect is returned. Until then an alert is return (like the ring tone until some one picks up the phone) –Phase 2: Running call The media streams (udp, red lines) are interchanged between the terminals directly A H.225/H.245 control channels are maintained between A and B –Phase 3: Hang up A sends be a DRQ B returns a DCF and the connection will be terminated

16 K. Stoeckigt, H.323 – The standard Endpoint GK direct Endpoint (usually 5 Phases, or 3 + 2) –Phase 1 (Call connect) A sends a ARQ to the Gatekeeper Gatekeeper then return ACF/ARJ A sends setup message to B B sends a ARQ to the Gatekeeper Gatekeeper returns ACF/ARJ B sends a connect or alert to A –Phase 2 (Running call) A and B exchanged RAS messages and media streams directly between each other. Signals are routed by the Gatekeeper –Phase 3 (Call termination) A sends DRQ to GK GK sends DRQ to B B returns DCF/DRJ to GK GK returns DCF/DRJ to A

17 K. Stoeckigt, H.323 – The standard Endpoint GK routed Endpoint –The phases are similar to the Endpoint GK direct Endpoint communication, however, in routed mode, the GK also routes the RAS messages

18 K. Stoeckigt, H.323 – The standard Endpoint GK proxy Endpoint –This scenario is not in the standard –Similar to the routed scenario, but the GK also routes the media streams you can bypass a firewall (more about it later)

19 K. Stoeckigt, H.323 – The standard All described scenarios can be extended to –Endpoint GK {direct|routed|proxy} GK {direct|routed|proxy} … Endpoint –Signaling will be the same for multipoint conferences via MCUs How do the endpoints find each other (assuming you dial an E.164 number)? –If both endpoints are on the same gatekeeper, the gatekeeper looks up the IP address in a local stack, or a back-end (DB, LDAP, etc.) –If the endpoints are on different Gatekeeper, LRQ (Location requests) are send to other known Gatekeeper (this is how GDS works wait for Egons talk about GDS)

20 K. Stoeckigt, H.323 – The standard some other extra features –Support for cascading MCUs –Far-end camera control –QoS information in H.460.9; the Gatekeeper could then change the route, if the endpoint reports a bad quality –Ability to utilize other network services, such as ENUM, DNS, LDAP, etc. –many other features

21 K. Stoeckigt, A recipe for successful H.323 videoconferencing You need –about 2 to 12kg of computer –20g to 5kg of webcam or videoconferencing system –ca. 50MB of Software –1 IP address, if possible without NAT(s) –1 fast piece of internet (if DSL min. 512kbit/s up/down-link) –if you want you can add a gatekeeper, an MCU or ISDN gateways –Put it together, let it settle for a couple of minutes in normal room temperature, one restart, and there you go…


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