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ATM

ATM. characteristics From an application-level API to the physical layer CBR, VBR, ABR and UBR Cell: 5 + 48 bytes Virtual circuits: virtual channel identifier (VCI) No retransmission on a link-by-link basis Congestion control only within the ATM ABR Run over any physical layer.

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ATM

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  1. ATM • characteristics • From an application-level API to the physical layer • CBR, VBR, ABR and UBR • Cell: 5 + 48 bytes • Virtual circuits: virtual channel identifier (VCI) • No retransmission on a link-by-link basis • Congestion control only within the ATM ABR • Run over any physical layer

  2. Fig 5.44 and 5.45

  3. Fig 5.47

  4. IP over ATM • Dynamic vs Permanent virtual channel • pp. 503-504 • Fig 5.52

  5. Myungchul Kim mckim@icu.ac.kr Ch 6. Multimedia Networking

  6. Networked multimedia applications: timing and tolerance of data loss • Delay-sensitive and loss-tolerant • Streaming stored audio and video • Stored media • Streaming: avoids having to download the entire file before beginning playout, Realplayer, QuickTime and Media Player • Continuous playout • Streaming live audio and video • Not stored, not fast-forward • Use the IP multicast

  7. Real-time interactive audio and video • Real-time • Interactive • Internet phone • For voice, 150 msec, 150-400 msec, 400 msec • Hurdles for multimedia • End-to-end delay for a packet • Variation of packet delay • Packet loss • Supporting multimedia better in Internet • Reservation approach • Laissez-faire approach: ISP, CDN, multicast overlay networks • Differentiation approach

  8. Audio and video compression • 1024 pixels * 1024 pixels with each pixel encoded into 24 bits => 3 Mbyte • 7 Min over a 64 kbps link • If the image is compressed at 10:1, • Audio compression • 8000 samples per second -> quantization with 256 values (8bits)-> 64,000 bits/second • Pulse code modulation • GSM, G.729, MPEG 1 layer 3(MP3),… • Video compression • MPEG 1, 2, 4, H.261

  9. Streaming stored audio and video • Real-time streaming protocol (RTSP) • User interactivity • RealPlayer and Media Player • Decompression, jitter removal, and correction • Fig 6.2

  10. Fig 6.3

  11. RTSP • Control the playback of continuous media • No related with compression schemes, encapsulation in packets, transportation, buffering • Out-of-band protocol • Over either TCP or UDP • Pause/resume, playback, fast-forward, and rewind

  12. Fig 6.5

  13. Internet phone • Every 20 msec over UDP • Packet loss, end-to-end delay, and packet jitter • Removing jitter at the receiver for audio • With a sequence number, a timestamp or • delaying playout at the receiver

  14. Fig 6.6

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