1

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

ATM

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

Ch 6. Multimedia Networking

Myungchul Kim

mckim@icu.ac.kr

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 begi

nning 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 Mbyt

e– 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)-> 64,0

00 bits/second– Pulse code modulation– GSM, G.729, MPEG 1 layer 3(MP3),…

Video compression– MPEG 1, 2, 4, H.261

9

Real-time streaming protocol (RTSP)– User interactivity– RealPlayer and Media Player– Decompression, jitter removal, and correction– Fig 6.2

Streaming stored audio and video

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

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

Internet phone

14

Fig 6.6