1. Technical Education Click here to move on Index Types of Conference Lesson 7

2. © Copyright Ezenia Inc, 2000 2 Lesson Objectives This lesson will look at the two main types of H.323 conferences, and the components necessary to make them work. It will look more closely at the role of the MCU within centralised conferences. The advantages and disadvantages of using different conference types will also be discussed. An understanding of how H.323 conferences are set up and operated, and the reasons for choosing the type of conference setup, is necessary when planning and designing a conference environment. It is also useful to understand the underlying reason why the setup to be supported has been designed in a particular way. Next Previous Beginning Help

3. © Copyright Ezenia Inc, 2000 3 Conference types Conferences will involve two, or more than two endpoints. To allow for maximum efficiencies, H.323 defines three types of conferences; Centralised, De-centralised and Hybrid. Before considering each type further, it is necessary to introduce two additional control functions into a conference; Multipoint Controller and Multipoint Processor. Explore what these are first.Multipoint ControllerMultipoint Processor Ok, now we can look at each type of conference – CentralisedCentralised, De-centralised and Hybrid.De-centralised Hybrid Previous Beginning Help Review Questions

4. © Copyright Ezenia Inc, 2000 4 Multipoint Controller  The Multipoint Controller decides which audio and video streams should be sent to all endpoints in the conference. It also negotiates between all parties as they join a conference to try to ensure compatible standards are used.  An MC is required for all multipoint conference types. It does not have to be a separate device and can be located in an endpoint for small conferences.  The MC operates the H.245 channel.  An MCU will be used for a large conference and that will contain an MC. Conference Types Beginning Help

5. © Copyright Ezenia Inc, 2000 5 Multipoint Processor  The Multipoint Processor receives and mixes the audio, and determines the selected video and data during the conference. It is essential for a centralised conference, and may be located within an endpoint. In practice the amount of processing by an MP in all but the smallest conference will dictate that the MP is in a separate specialist device - the MCU. Beginning Help Conference Types

6. © Copyright Ezenia Inc, 2000 6 Centralised conference Each endpoint transmits its conference control, audio, video and data streams to the MCU which contains both the MP and MC. The MP processes the incoming information and produces an audio conference mix which it transmits to all endpoints. The MP selects which of the incoming video streams is to be used and broadcasts that to all endpoints. Using RTCP, two video signals will be received by the MCU (the loudest and next loudest), these will be retransmitted, all other video signals will be stopped at source until the loudest site changes. The MC manages the conference operating parameters. Beginning Help Conference Types How does this work?

7. © Copyright Ezenia Inc, 2000 7 Centralised conference Previous Beginning Help MCU MP MC Audio, Video and Data H.245 Control Centralised conferences use Unicast transmission, that is one way, single destination. I.e. from originator to MCU and from MCU to each individual endpoint that requires the signal. This is the most efficient system in terms of network bandwidth available with most currently installed routers. Can I see this in more detail?

8. © Copyright Ezenia Inc, 2000 8 Step 1 An endpoint registers with the Gatekeeper. Step 2At some time in the future a conference is required. “MC” in the MCU calls the Gatekeeper to register conference “meeting96”. Step 3Gatekeeper registers and responds that conference may proceed. How a centralised conference happens Next Previous Beginning Help 2. Register conference ‘meeting96’ 3. Conference ‘meeting96’ may proceed 1. Register ‘Dave’ Dave Legend H.225/Q.931 H225/RAS H.245 RTP other

9. © Copyright Ezenia Inc, 2000 9 How a centralised conference happens Next Previous Beginning Help Legend H.225/Q.931 H225/RAS H.245 RTP other Dave 4. Name of conference? Step 4Dave” is a participant in the conference. He uses the Browser interface to establish the name of the conference.

10. © Copyright Ezenia Inc, 2000 10 How a centralised conference happens Next Previous Beginning Help Dave 5. Can I connect to ‘meeting96’ at 384 kbps 6. Yes; use IP address 23.46.147.11 Legend H.225/Q.931 H225/RAS H.245 RTP other Step 5Endpoint calls Gatekeeper to request connection to “Meeting96”, and indicates required bandwidth. Step 6Gatekeeper negotiates with the endpoint over bandwidth if necessary and able, then responds positively (in this example), and provides the IP address to be used.

11. © Copyright Ezenia Inc, 2000 11 How a centralised conference happens Next Previous Beginning Help Dave Legend H.225/Q.931 H225/RAS H.245 RTP other Step 7Endpoint calls MCU conference “Meeting96” directly. Step 8“Meeting96” checks with Gatekeeper that it can accept the call. Step 9Gatekeeper responds positively if sufficient bandwidth is available. 7. Hello ‘meeting96’ 8. Can I accept call from ‘Dave’ at 384 kbps 9. yes

12. © Copyright Ezenia Inc, 2000 12 How a centralised conference happens Next Previous Beginning Help Dave Legend H.225/Q.931 H225/RAS H.245 RTP other Step 10MCU confirms “Dave” is a participant in the conference “Meeting96”. Step 11MC in MCU communicates with “Dave” and agrees standards to be used for audio and video. (H.245) 11. Hello ‘Dave’ What parameters can you use? 10. Is ‘Dave’ in ‘meeting 96’

13. © Copyright Ezenia Inc, 2000 13 How a centralised conference happens Next Previous Beginning Help Legend H.225/Q.931 H225/RAS H.245 RTP other Step 12Endpoint “Mary” requires to join conference. Conducts conversation with Gatekeeper to gain admission. (H.225/Q.931/RAS) Step 13“Mary” requests connection to “MCU” at 768 kbps. (H.225/Q.931/RAS) Mary 13. Hello ‘meeting96’ Dave 12a. Can I connect to ‘meeting96’ at 768 kbps? 12b.yes - use IP address 23.46.147.11

14. © Copyright Ezenia Inc, 2000 14 How a centralised conference happens Next Previous Beginning Help Legend H.225/Q.931 H225/RAS H.245 RTP other Step 14MCU requests acceptance from Gatekeeper. Step 15MCU specifies audio and video operating parameters. Step 16“Mary” joins conference. (H.245) Note - “Mary” has joined the conference at 768 kbps; “Dave” is operating at 384 kbps, and this has set the ruling speed for the conference video to 384k. Dave Mary 15. Use these parameters 14a. Can I talk to ‘Mary’ 14b. yes 16. ‘Mary’ joins conference

15. © Copyright Ezenia Inc, 2000 15 How a centralised conference happens Conference Types Previous Beginning Help Legend H.225/Q.931 H225/RAS H.245 RTP other Step 17Dave chooses to leave the conference, and notifies the MCU and the Gatekeeper. (H.225/RAS) Step 18MCU advises the Gatekeeper that the connection to “Dave” has ended. (H.225/RAS) Dave Mary 17. End connection to “meeting 96” 17. End connection 18. Connection to “Dave” ended

16. © Copyright Ezenia Inc, 2000 16 Decentralised conference Each endpoint transmits its audio, video and data to every other endpoint in the conference. An MC must be present (it may be co-located with an endpoint, in an MCU, or other device). The MC manages the H.245 control channel with each endpoint in the conference. No MP is required because each endpoint is sending the audio, video and data streams to everyone else in the conference. Each endpoint manages the received input and selects a video stream and mixes the audio. Conference control is unicast in this case, but everything else can be multicast. This means that decentralised is only suitable for very small conferences Beginning Help Conference Types Why is this not suitable for large conferences?

17. © Copyright Ezenia Inc, 2000 17 Decentralised conference Beginning Help While there is not very much H.323 traffic associated with this 4 seat conference, just adding 1 More user dramatically increases the amount of traffic. Audio, Video and Data H.245 Control MC This page is animated. Please wait for it to finish. Conference Types

18. © Copyright Ezenia Inc, 2000 18 Hybrid conference Beginning Help MCU MP MC Audio, Video and Data H.245 Control MC In this mixed conference some endpoints are in a centralised conference, while others are in a decentralised conference. The endpoints are not aware of the mixed nature of the conference. In the decentralised part of the conference the MCU acts as a composite endpoint for all those endpoints that are in the centralised conference. Conference Types

19. © Copyright Ezenia Inc, 2000 19  An MCU is not necessary for a de-centralised conference.  True  False Review Question 1 Beginning Help Review that information again Move on to the next question Conference Types

20. © Copyright Ezenia Inc, 2000 20  An MC is necessary for any type of conference. An MCU is not necessary for a de-centralised conference. Wrong Answer Review that information again Beginning Help Move on to the next question Conference Types

21. © Copyright Ezenia Inc, 2000 21 Correct Answer Review that information again Well done An MCU is not necessary for a de-centralised conference. Beginning Help Move on to the next question Conference Types

22. © Copyright Ezenia Inc, 2000 22  Which of the following is not a benefit of running centralised conferences?  Less network bandwidth used for  H.323 traffic  Less overhead in endpoints as  MP is centrally located  Gatekeeper is not used Review Question 2 Beginning Help Review that information again Previous Question Move on to the next question

23. © Copyright Ezenia Inc, 2000 23  As all traffic in a centralised conference is unicast, between MCU and endpoints, there is less traffic in such a conference. Also, as the MP in the MCU sorts out the audio and video streams, and source quenches any video that is not needed, there is less H.323 data on the network. The Gatekeeper is always involved in any H.323 conference set up, if there is a Gatekeeper present. Wrong Answer Review that information again Beginning Help Previous Question Move on to the next question

24. © Copyright Ezenia Inc, 2000 24  In any type of conference there must be an MC function. If there is no MCU, one of the endpoints must perform that function. This could have a detrimental effect on that endpoint’s performance. The Gatekeeper is always involved in any H.323 conference set up, if there is a Gatekeeper present. Wrong Answer Review that information again Beginning Help Previous Question Move on to the next question

25. © Copyright Ezenia Inc, 2000 25 Correct Answer Review that information again Well done The Gatekeeper is always involved in any H.323 conference set up, if there is a Gatekeeper present. Beginning Help Previous Question Move on to the next question

26. © Copyright Ezenia Inc, 2000 26  Which of the following is a function of a Multipoint Controller?  Registering endpoints  Source Quenching unwanted Video streams  Negotiating conference operating parameters Review Question 3 Beginning Help Review that information again Previous Question Move on to the next question

27. © Copyright Ezenia Inc, 2000 27  This is a function of the Gatekeeper. The MC must be present in all conference and it decides which audio and video streams will be used in a conference, and negotiates the operating parameters of that conference. Wrong Answer Beginning Help Previous Question Review that information again Move on to the next question

28. © Copyright Ezenia Inc, 2000 28  This is a function of the MP, found in centralised conferences. The MC must be present in all conference and it decides which audio and video streams will be used in a conference, and negotiates the operating parameters of that conference. Wrong Answer Beginning Help Previous Question Review that information again Move on to the next question

29. © Copyright Ezenia Inc, 2000 29 Correct Answer Well done The MC must be present in all conference and it decides which audio and video streams will be used in a conference, and negotiates the operating parameters of that conference. Beginning Help Previous Question Review that information again Move on to the next question

30. © Copyright Ezenia Inc, 2000 30  The MCU appears as another endpoint to the endpoints in the decentralised part of a hybrid conference?  True  False Review Question 4 Beginning Help Review that information again Previous Question

31. © Copyright Ezenia Inc, 2000 31  Endpoints in a de-centralised conference will not recognise what an MCU is. As an MCU mixes the signals for the endpoints it manages, it has to present that information to those endpoints outside its area. The MCU will appear as a composite endpoint for all those endpoints that are in the centralised conference. Wrong Answer Review that information again Beginning Help Previous Question

32. © Copyright Ezenia Inc, 2000 32 Correct Answer Review that information again Well done The MCU will appear as a composite endpoint for all those endpoints that are in the centralised conference. Beginning Help Previous Question