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Chapter 28.Network Management

Chapter 29.Multimedia

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Network Management System and SNMP Concepts

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Internet Audio/Video

• Streaming stored audio/video refers to on-demand requests for compressed audio/video files

• Streaming live audio/video refers to the broadcasting of radio and TV programs through the Internet

• Interactive audio/video refers to the use of the Internet for interactive audio/video applications

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Digitizing Audio and Video

• Digitizing audio– Voice: 64 Kbps = 8,000 samples x 8 bits– Music: 44,100 samples x 16 bits -> 705.6 Kbps for mono, 1,411 Mbps for stereo

• Digitizing video– 25 frames/second, 1024 x 768 pixels, 24 bits/pixel– 2 x 25 x 1024 x 768 x 24 = 944 Mbps

• Compression is needed to send video (audio) over the Internet

• Audio Compression– Predictive encoding: GSM(13Kbps), G.729(8Kbps), G.723.3(6.4 or 5.3 Kbps)– Perceptual encoding: MP3 (MPEG audio layer 3)

• Video Compression– Image compression: JPEG– Video compression: MPEG

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Streaming Stored AV: (1)

• First approach: Using a Web server

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Streaming Stored AV: (2)

• Second approach: Using a Web server with metafile

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Streaming Stored AV: (3)

• Third approach: Using a media server

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Streaming Stored AV: (4)

• Fourth approach: Using a media server and RTSP

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Real-time Interactive AV

• Time relationship

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Real-time Interactive AV

• Jitter is introduced in real-time data by the delay between packets

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Timestamp

• To prevent jitter, we can timestamp the packets and separate the arrival time from the playback time

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Playback Buffer

• A playback buffer is required for real-time traffic

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Characteristics of Real-time AV Communication

• A sequence number on each packet is required for real-time traffic

• Real-time traffic needs the support of multicasting

• Translation means changing the encoding of a payload to a lower quality to match the bandwidth of the receiving network

• Mixing means combining several streams of traffic into one stream.

• Support from transport layer protocol

• TCP, with all its sophistication, is not suitable for interactive multimedia traffic because we cannot allow retransmission of packets.

• UDP 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

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Real-time Transport Protocol (RTP)

• RTP is designed to handle real-time traffic on the Internet

• RTP uses a temporary even-numbered UDP port

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Real-time Transport Control Protocol (RTCP)

• RTCP is designed to control the flow and quality of data and allow the recipient to send feedback to the source or sources

• RTCP uses an odd-numbered UDP port number that follows the port number selected for RTP

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Voice over IP

• Session Initiation Protocol (SIP) by IETF and H.323 by ITU-T

• SIP

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SIP Simple Session

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Tracking the Callee

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H.323 Architecture and Protocols

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H.323 Example