Figure 15.1 A distributed multimedia system

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A distributed multimedia system ... and Kindberg Distributed Systems: Concepts and Design Edn. 3 © Pearson ... Characteristics of typical multimedia streams.
Figure 15.1

A distributed multimedia system

Video camera and mike

Local network

Local network

Wide area gateway

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

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Video server

Digital TV/radio server

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Figure 15.2

The window of scarcity for computing and communication resources interactive video

high-quality audio

insufficient resources

scarce resources

abundant resources

network file access

remote login 1980

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

1990

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2000

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Figure 15.3

Characteristics of typical multimedia streams Data rate (approximate)

Sample or frame size frequency

Telephone speech

64 kbps

CD-quality sound

1.4 Mbps

Standard TV video (uncompressed)

120 Mbps

up to 640 × 480 pixels × 16 bits

24/sec

Standard TV video (MPEG-1 compressed)

1.5 Mbps

variable

24/sec

1000–3000 Mbps

up to 1920 × 1080 pixels × 24 bits

24–60/sec

10–30 Mbps

variable

24–60/sec

HDTV video (uncompressed) HDTV video (MPEG-2 compressed)

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

8 bits

8000/sec

16 bits 44,000/sec

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Figure 15.4

Typical infrastructure components for multimedia applications PC/workstation

PC/workstation Window system

Camera

K

A

G Codec

Codec

Microphones

Screen

B

H

L Mixer Network connections

C

Video file system D Codec

M

Video store

Window system : multimedia stream White boxes represent media processing components, many of which are implemented in software, including:

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

© Pearson Education 2001

codec: coding/decoding filter mixer: sound-mixing component

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Figure 15.5

QoS specifications for components of the application shown in Figure 15.4

Component Camera

Bandwidth

Latency

Loss rate

Resources required

Zero



Out:

10 frames/sec, raw video 640x480x16 bits



A Codec

In: Out:

10 frames/sec, raw video MPEG-1 stream

Interactive Low

10 ms CPU each 100 ms; 10 Mbytes RAM

B Mixer

In: Out:

2 × 44 kbps audio

Interactive Very low

1 × 44 kbps audio

1 ms CPU each 100 ms; 1 Mbytes RAM

In: Out:

various Interactive Low 50 frame/sec framebuffer

5 ms CPU each 100 ms; 5 Mbytes RAM

H Window system

K Network In/Out: MPEG-1 stream, connection approx. 1.5 Mbps

Interactive Low

1.5 Mbps, low-loss stream protocol

L

Interactive Very low

44 kbps, very low-loss stream protocol

Network In/Out: Audio 44 kbps connection

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

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Figure 15.6

The QoS manager’s task

Admission control

QoS negotiation Application components specify their QoS requirements to QoS manager Flow spec. QoS manager evaluates new requirements against the available resources. Sufficient? Yes No

Reserve the requested resources Resource contract

Negotiate reduced resource provision with application. Agreement? Yes No

Allow application to proceed

Application runs with resources as per resource contract

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

Do not allow application to proceed Application notifies QoS manager of increased resource requirements

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6

Figure 15.7

Traffic shaping algorithms (a) Leaky bucket

(b) Token bucket

Token generator

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

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Figure 15.8

The RFC 1363 Flow Spec Protocol version Maximum transmission unit Bandwidth:

Token bucket rate Token bucket size Maximum transmission rate Minimum delay noticed

Delay: Maximum delay variation Loss sensitivity Loss:

Burst loss sensitivity Loss interval Quality of guarantee

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Figure 15.9

Filtering

Source

Targets

High bandwidth Medium bandwidth Low bandwidth

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

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9

Figure 15.10

Tiger video file server hardware configuration

Controller low-bandwidth network 0

n+1

Cub 0

1

n+2

Cub 1

2

n+3

Cub 2

3

n+4

Cub 3

n

2n+1

Cub n

high-bandwidth ATM switching network

video distribution to clients

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

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Start/Stop requests from clients

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Figure 15.11

Tiger schedule

2 slot 0 viewer 4 state

slot 1 free

block play time T slot 2 free

slot 3 viewer 0 state

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

block service time t

1 slot 4 viewer 3 state

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slot 5 viewer 2 state

0 slot 6 free

slot 7 viewer 1 state

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