Bài giảng TCP/IP Protocol Suite - Chapter 25: Multimedia

Chapter 25Upon completion you will be able to:Multimedia Know the characteristics of the 3 types of services Understand the methods of digitizing and compressing. Understand jitter, translation, and mixing in real-time traffic Understand the role of RTP and RTCP in real-time traffic Understand how the Internet can be used as a telephone networkObjectives 1TCP/IP Protocol SuiteFigure 25.1 Internet audio/video2TCP/IP Protocol SuiteStreaming stored audio/video refers to on-demand requests for compressedaudio/video files.Note:3TCP/IP Protocol SuiteStreaming live audio/video refers to the broadcasting of radio and TV programs through the Internet.Note:4TCP/IP Protocol SuiteInteractive audio/video refers to the use of the Internet for interactive audio/video applications.Note:5TCP/IP Protocol Suite25.1 DIGITIZING AUDIO AND VIDEOBefore audio or video signals can be sent on the Internet, they need to be digitized. We discuss audio and video separately.The topics discussed in this section include:Digitizing Audio Digitizing Video 6TCP/IP Protocol SuiteCompression is needed to send video over the Internet.Note:7TCP/IP Protocol Suite25.2 AUDIO AND VIDEO  COMPRESSIONTo send audio or video over the Internet requires compression. The topics discussed in this section include:Audio Compression Video Compression 8TCP/IP Protocol SuiteFigure 25.2 JPEG gray scale9TCP/IP Protocol SuiteFigure 25.3 JPEG process10TCP/IP Protocol SuiteFigure 25.4 Case 1: uniform gray scale11TCP/IP Protocol SuiteFigure 25.5 Case 2: two sections12TCP/IP Protocol SuiteFigure 25.6 Case 3: gradient gray scale13TCP/IP Protocol SuiteFigure 25.7 Reading the table14TCP/IP Protocol SuiteFigure 25.8 MPEG frames15TCP/IP Protocol SuiteFigure 25.9 MPEG frame construction16TCP/IP Protocol Suite25.3 STREAMING STORED AUDIO/VIDEOWe turn our attention to a specific applications called streaming stored audio and video. We use four approaches to show how a file can be downloaded, each with a different complexity.The topics discussed in this section include:First Approach: Using a Web Server Second Approach: Using a Web Server with Metafile Third Approach: Using a Media Server Fourth Approach: Using a Media Server and RTSP 17TCP/IP Protocol SuiteFigure 25.10 Using a Web server18TCP/IP Protocol SuiteFigure 25.11 Using a Web server with a metafile19TCP/IP Protocol SuiteFigure 25.12 Using a media server20TCP/IP Protocol SuiteFigure 25.13 Using a media server and RTSP21TCP/IP Protocol Suite25.4 STREAMING LIVE  AUDIO/VIDEOIn streaming live audio/video the stations broadcast through the Internet. Communication is multicast and live. Live streaming is better suited to the multicast services of IP and the use of protocols such as UDP and RTP.22TCP/IP Protocol Suite25.5 REAL-TIME INTERACTIVE  AUDIO/VIDEOIn real-time interactive audio/video, people communicate visually and orally with one another in real time. Examples include video conferencing and the Internet phone or voice over IP. The topics discussed in this section include:Characteristics 23TCP/IP Protocol SuiteFigure 25.14 Time relationship24TCP/IP Protocol SuiteJitter is introduced in real-time data by the delay between packets.Note:25TCP/IP Protocol SuiteFigure 25.15 Jitter26TCP/IP Protocol SuiteFigure 25.16 Timestamp27TCP/IP Protocol SuiteTo prevent jitter, we can timestamp the packets and separate the arrival time from the playback time.Note:28TCP/IP Protocol SuiteFigure 25.17 Playback buffer29TCP/IP Protocol SuiteA playback buffer is required forreal-time traffic.Note:30TCP/IP Protocol SuiteA sequence number on each packet is required for real-time traffic.Note:31TCP/IP Protocol SuiteReal-time traffic needs the support of multicasting.Note:32TCP/IP Protocol SuiteTranslation means changing the encoding of a payload to a lower quality to match the bandwidthof the receiving network.Note:33TCP/IP Protocol SuiteMixing means combining several streams of traffic into one stream.Note:34TCP/IP Protocol SuiteTCP, with all its sophistication, is not suitable for interactive multimedia traffic because we cannot allow retransmission of packets.Note:35TCP/IP Protocol SuiteUDP is more suitable than TCP for interactive traffic. However, we need the services of RTP, another transport layer protocol, to make up for the deficiencies of UDP.Note:36TCP/IP Protocol Suite25.6 RTPReal-time Transport Protocol (RTP) is the protocol designed to handle real-time traffic on the Internet. RTP does not have a delivery mechanism; it must be used with UDP.The topics discussed in this section include:RTP Packet Format UDP Port 37TCP/IP Protocol SuiteFigure 25.18 RTP38TCP/IP Protocol SuiteFigure 25.19 RTP packet header format39TCP/IP Protocol SuiteTable 25.1 Payload types40TCP/IP Protocol SuiteRTP uses a temporary even-numbered UDP port.Note:41TCP/IP Protocol Suite25.7 RTCPReal-time Transport Control Protocol (RTCP) is a protocol that allows messages that control the flow and quality of data. RTCP has five types of messages.The topics discussed in this section include:Sender Report Receiver Report Source Description Message Bye Message Application Specific Message UDP Port 42TCP/IP Protocol SuiteFigure 25.20 RTCP message types43TCP/IP Protocol SuiteRTCP uses an odd-numbered UDP port number that follows the port number selected for RTP.Note:44TCP/IP Protocol Suite25.8 VOICE OVER IPVoice over IP, or Internet telephony is an application that allows communication between two parties over the packet-switched Internet. Two protocols have been designed to handle this type of communication: SIP and H.323. The topics discussed in this section include:SIP H.323 45TCP/IP Protocol SuiteFigure 25.21 SIP messages46TCP/IP Protocol SuiteFigure 25.22 SIP formats47TCP/IP Protocol SuiteFigure 25.23 SIP simple session48TCP/IP Protocol SuiteFigure 25.24 Tracking the callee49TCP/IP Protocol SuiteFigure 25.25 H.323 architecture50TCP/IP Protocol SuiteFigure 25.26 H.323 protocols51TCP/IP Protocol SuiteFigure 25.27 H.323 example52TCP/IP Protocol Suite