1. T.Sharon-A.Frank 1 Multimedia Group Communication Synchronization Standards

2. 2 T.Sharon-A.Frank Major Issues 1. Size of Data Frame 2. Need High Bandwidth 3. Digital vs. Analog Representation 4. Multi-Modality Integration/Blending 5. Soft Real-Time Constraints 6. Need Group Communication 7. Need Synchronization 8. Need for Standards

3. 3 T.Sharon-A.Frank 6. Need Group Communication

4. 4 T.Sharon-A.Frank Group Communication Wide Area Network Amsterdam London New York Tel-Aviv Multicast

5. 5 T.Sharon-A.Frank Casting Terms Three general methods for delivering content from a server to a client across a network: (1) Unicasting – the server delivers the content to a single client. (2) Broadcasting – the server delivers the content to all clients, regardless whether they want the content or not. (3) Multicasting – the server delivers the content to a group of receivers who indicate they wish to receive the content.

6. 6 T.Sharon-A.Frank Casting relationships Unicast: one sender – one receiver Multicast: one sender – many receivers Broadcast: one sender – all receive Unicast and Broadcast are actually special cases of multicast MulticastBroadcast

7. 7 T.Sharon-A.Frank Unicast vs. Multicast

8. 8 T.Sharon-A.Frank Solution Use Multicast Show/See Flash!

9. 9 T.Sharon-A.Frank 7. Need Synchronization

10. 10 T.Sharon-A.Frank Synchronization Problem London New-York Tel-Aviv Amsterdam Montreal Rotterdam 1.Between media (e.g. lipsynch) 2.Between users in group (orchestration)

11. 11 T.Sharon-A.Frank Synchronization Markers Use buffering to synch Might increase overall delay and jitter

12. 12 T.Sharon-A.Frank Solutions Synchronization Markers Use Delay (buffers) Show/See Flash!

13. 13 T.Sharon-A.Frank 8. Need for Standards Question: What ’ s good about a standard? Answer: there are MANY of them.

14. 14 "Standards are documented agreements containing technical specifications … to be used consistently … to ensure that materials, products, processes and services are fit for their purpose." (ISO) Ensure things that conform to standards are interchangeable. Multimedia standards concern file formats, markup languages etc, and especially network protocols. Standards

15. 15 ISO (International Organization for Standards) – All technical fields except electrical and electronic engineering IEC (International Electrotechnical Commission) ITU (International Telecommunications Union) – IT dealt with by joint ISO/IEC technical committee Standards Organizations

16. 16 Internet Architecture Board (IAB) – Internet Engineering Task Force (IETF) deals with technical development. – Internet Assigned Numbers Authority (IANA) registers MIME types, language codes, etc. World Wide Web Consortium (W3C) – No official status, but Recommendations are treated as standards for the WWW. Internet Standards

17. 17 T.Sharon-A.Frank Map to ISO-OSI Model (7 Layers) Application Presentation Session Transport Network Data Link Physical Fit For Multimedia? Solution: Twist OSI Model

18. Interconnected Subnetworks Local Area Private Dedicated Public Circuit Switched Metropolitan Area Public Packet Switched Local Area Bridge Gateway Router Gateway Router ISDN M a s s Networks e

19. 19 T.Sharon-A.Frank Multimedia Users

20. 20 T.Sharon-A.Frank Categorization of Multimedia Standards