1. Chapter 5: Summary r principles behind data link layer services: m error detection, correction m multiple access protocols m link layer addressing, ARP r link layer technologies: Ethernet, interconnecting, IEEE 802.11 LANs, PPP, … r journey down the protocol stack is done m Remaining 3 weeks: multimedia, …

2. Chapter 6 Multimedia Networking These lecture notes are based heavily on slides provided by the authors of the book. All material should be considered as belonging to their copyright. For this course, I have made changes (and deletions/additions to the lecture notes). All material copyright 1996-2002 J.F Kurose and K.W. Ross, All Rights Reservedç Computer Networking: A Top Down Approach Featuring the Internet, 2 nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002.

3. Chapter 6: Goals Principles r Classify multimedia applications r Identify the network services the apps need r Making the best of best effort service r Mechanisms for providing QoS Protocols and Architectures r Specific protocols for best-effort r Architectures for QoS

4. Chapter 6 outline r 6.1 Multimedia Networking Applications r 6.2 Streaming stored audio and video m RTSP r 6.3 Real-time Multimedia: Internet Phone Case Study r 6.4 Protocols for Real- Time Interactive Applications m RTP,RTCP m SIP r 6.5 Beyond Best Effort r 6.6 Scheduling and Policing Mechanisms r 6.7 Integrated Services r 6.8 RSVP r 6.9 Differentiated Services Others?

5. A general view of multimedia protocols

6. MM Networking Applications Fundamental characteristics: r Typically delay sensitive m end-to-end delay m delay jitter r But loss tolerant: infrequent losses cause minor glitches r Antithesis of data, which are loss intolerant but delay tolerant. Classes of MM applications: 1) Streaming stored audio and video 2) Streaming live audio and video 3) Real-time interactive audio and video Jitter is the variability of packet delays within the same packet stream

7. Streaming Stored Multimedia Streaming: r media stored at source r transmitted to client r streaming: client playout begins before all data has arrived r timing constraint for still-to-be transmitted data: in time for playout

8. Streaming Stored Multimedia: What is it? 1. video recorded 2. video sent 3. video received, played out at client Cumulative data streaming: at this time, client playing out early part of video, while server still sending later part of video network delay time

9. Streaming Stored Multimedia: Interactivity r VCR-like functionality: client can pause, rewind, FF, push slider bar m 10 sec initial delay OK m 1-2 sec until command effect OK m RTSP often used (more later) r timing constraint for still-to-be transmitted data: in time for playout

10. Streaming Live Multimedia Examples: r Internet radio talk show r Live sporting event Streaming r playback buffer r playback can lag tens of seconds after transmission r still have timing constraint Interactivity r fast forward impossible r rewind, pause possible!

11. Interactive, Real-Time Multimedia r end-end delay requirements: m audio: < 150 msec good, < 400 msec OK includes application-level (packetization) and network delays higher delays noticeable, impair interactivity r session initialization m how does callee advertise its IP address, port number, encoding algorithms? r applications: IP telephony, video conference, distributed interactive worlds

12. Multimedia Over Today’s Internet TCP/UDP/IP: “best-effort service” r no guarantees on delay, loss Today’s Internet multimedia applications often use application-level techniques to mitigate (as best possible) effects of delay, loss But multimedia apps require QoS and level of performance to be effective! ? ? ?? ? ? ? ? ? ? ?

13. How should the Internet evolve to better support multimedia? Integrated services philosophy: r Fundamental changes in Internet so that apps can reserve end-to-end bandwidth r Requires new, complex software in hosts & routers More bandwidth, more servers… r no major changes r more bandwidth when needed r content distribution, application-layer multicast m application layer Differentiated services philosophy: r Fewer changes to Internet infrastructure, yet provide 1st and 2nd class service. What’s your opinion?