Transcript
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
© Pearson Education 2001
Video server
Digital TV/radio server
1
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
© Pearson Education 2001
2000
2
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
© Pearson Education 2001
3
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
4
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
© Pearson Education 2001
5
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
© Pearson Education 2001
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
© Pearson Education 2001
7
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
Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3
© Pearson Education 2001
8
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
© Pearson Education 2001
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
© Pearson Education 2001
Start/Stop requests from clients
10
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
© Pearson Education 2001
slot 5 viewer 2 state
0 slot 6 free
slot 7 viewer 1 state
11
