多媒体通信网络英文课件Chapter2 Multimedia Networks.ppt

MMCN-Chapter2 Chapter 2 Multimedia Networks: Requirements and Performance Issues Prof. Guohui Li School of Information System and Management National University of Defense Technology Spring 2010 Chapter 2 2.1 Distributed multimedia applications 2.2 Peer-to-Peer and multi-peer communications 2.3 Performance parameters 2.4 Quality of Service 2.5 Multimedia transmission requirements 2.6 Summary 2.1 Distributed multimedia applications Issues To make the discussion of multimedia transmission requirements more concrete, we start by discussing a few commonly used multimedia applications. How do these applications work and what characteristics are there for these applications. 2.1 Distributed multimedia applications 1. Audio and video streams Streaming audio and video applications (e.g. Realplayer, Winamp, etc. live radio and broadcast) enable you to listen to or view program as it is being transferred. During their travel across the network, the packets suffer variable delays. The destination buffers a few packets before it starts playing them back as an audio or video stream. The buffering absorbs the delay fluctuations. 2.1 Distributed multimedia applications 2. Video conferencing For conversations, the one way delay is barely noticeable if it is less than 100 ms. Beyond 350 ms, the delay makes the conversation unpleasant. Small delay requirement of voice implies that voice samples must be placed in small packets. Packetization will introduce some of delays that add to overall end-to-end delay. 2.1 Distributed multimedia applications 3. World Wide Web-WWW WWW is a distributed application that enables you to navigate through a set of hyperlinked documents, called Web pages. Each Web page may contain text, pictures, audio clips, video clips, and possibly links. When you browse the Web, you initiate a sequence of file transfers according to HTTP. Actually, audio/video stream, video conferencing, video on demand can be Internet applications. 2.2 Peer-to-Peer and mu