高级计算机网络课件Chapter7_4th_ed_June_25_2007讲述.ppt

Multimedia and Quality of Service: What is it? Chapter 7: goals( still on the way) Principles classify multimedia applications identify network services applications need Mak(e)ing the best (充分利用) of best effort service尽力而为的服务 Protocols and Architectures specific protocols for best-effort mechanisms for providing QoS architectures for QoS Chapter 7 outline 7.1 multimedia networking applications 7.2 streaming stored audio and video 7.3 making the best out of best effort service 7.4 protocols for real-time interactive applications RTP,RTCP,SIP 7.5 providing multiple classes of service 7.6 providing QoS guarantees MM Networking Applications Fundamental characteristics: typically delay sensitive end-to-end delay delay jitter loss tolerant: infrequent losses cause minor glitches小干扰 antithesis对立而言 of data, which are loss intolerant but delay tolerant. Classes of MM applications: 1) stored streaming流式存储 2) live streaming流式实况 3) interactive, real-time实时交互 另:Download--then-play(mp3)? Streaming Stored Multimedia Streaming Stored Multimedia: What is it? Streaming Stored Multimedia: Interactivity Streaming Live Multimedia Examples: Internet radio talk show脱口秀 live sporting event Streaming (as with streaming stored multimedia) playback buffer playback can lag滞后tens of seconds after transmission still have timing constraint Interactivity fast forward impossible rewind, pause possible! Real-Time Interactive Multimedia end-end delay requirements: audio: 150 msec good, 400 msec OK includes application-level (packetization) and network delays higher delays noticeable, impair削弱interactivity session initialization how does callee被呼者 advertise its IP address, port number, encoding algorithms? Multimedia Over Today’s Internet TCP/UDP/IP: “best-effort service” no guarantees on delay, loss包括端端延迟、流中分组时延变化和丢失 How should the Internet evolve to better support multimedia? Integrated services philosophy: fundamental changes in Internet so that apps can reserve end-to-end bandw