Chapter 6 Broadband
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The following figure illustrates the relationship between PCR, SCR and MBS.
Figure 27
Example of Traffic Shaping
ATM Traffic Classes
These are the basic ATM traffic classes defined by the ATM Forum Traffic Management 4.0
Specification.
Constant Bit Rate (CBR)
Constant Bit Rate (CBR) provides fixed bandwidth that is always available even if no data is being
sent. CBR traffic is generally time-sensitive (doesn't tolerate delay). CBR is used for connections
that continuously require a specific amount of bandwidth. A PCR is specified and if traffic exceeds
this rate, cells may be dropped. Examples of connections that need CBR would be high-resolution
video and voice.
Variable Bit Rate (VBR)
The Variable Bit Rate (VBR) ATM traffic class is used with bursty connections. Connections that use
the Variable Bit Rate (VBR) traffic class can be grouped into real time (VBR-RT) or non-real time
(VBR-nRT) connections.
The VBR-RT (real-time Variable Bit Rate) type is used with bursty connections that require closely
controlled delay and delay variation. It also provides a fixed amount of bandwidth (a PCR is
specified) but is only available when data is being sent. An example of an VBR-RT connection would
be video conferencing. Video conferencing requires real-time data transfers and the bandwidth
requirement varies in proportion to the video image's changing dynamics.
The VBR-nRT (non real-time Variable Bit Rate) type is used with bursty connections that do not
require closely controlled delay and delay variation. It is commonly used for "bursty" traffic typical
on LANs. PCR and MBS define the burst levels, SCR defines the minimum level. An example of an
VBR-nRT connection would be non-time sensitive data file transfers.
Unspecified Bit Rate (UBR)
The Unspecified Bit Rate (UBR) ATM traffic class is for bursty data transfers. However, UBR doesn't
guarantee any bandwidth and only delivers traffic when the network has spare bandwidth. An
example application is background file transfer.
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Страница 8: ...Contents Overview VMG1312 B10A User s Guide 8 Troubleshooting 291 ...
Страница 18: ...Table of Contents VMG1312 B10A User s Guide 18 ...
Страница 19: ...19 PART I User s Guide ...
Страница 20: ...20 ...
Страница 34: ...Chapter 2 The Web Configurator VMG1312 B10A User s Guide 34 ...
Страница 39: ...Chapter 4 Tutorials VMG1312 B10A User s Guide 39 7 Click Apply to save your settings ...
Страница 79: ...79 PART II Technical Reference ...
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Страница 168: ...Chapter 9 Routing VMG1312 B10A User s Guide 168 ...
Страница 186: ...Chapter 10 Quality of Service QoS VMG1312 B10A User s Guide 186 ...
Страница 212: ...Chapter 13 Interface Group VMG1312 B10A User s Guide 212 ...
Страница 228: ...Chapter 15 Firewall VMG1312 B10A User s Guide 228 ...
Страница 234: ...Chapter 17 Parental Control VMG1312 B10A User s Guide 234 ...
Страница 244: ...Chapter 19 Certificates VMG1312 B10A User s Guide 244 ...
Страница 248: ...Chapter 20 Log VMG1312 B10A User s Guide 248 ...
Страница 252: ...Chapter 21 Traffic Status VMG1312 B10A User s Guide 252 ...
Страница 258: ...Chapter 24 IGMP Status VMG1312 B10A User s Guide 258 ...
Страница 262: ...Chapter 25 xDSL Statistics VMG1312 B10A User s Guide 262 ...
Страница 264: ...Chapter 26 User Account VMG1312 B10A User s Guide 264 ...
Страница 270: ...Chapter 29 TR 064 VMG1312 B10A User s Guide 270 ...
Страница 274: ...Chapter 30 Time Settings VMG1312 B10A User s Guide 274 ...
Страница 280: ...Chapter 32 Logs Setting VMG1312 B10A User s Guide 280 ...
Страница 298: ...Chapter 36 Troubleshooting VMG1312 B10A User s Guide 298 ...
Страница 338: ...Appendix C Pop up Windows JavaScripts and Java Permissions VMG1312 B10A User s Guide 338 ...
Страница 352: ...Appendix D Wireless LANs VMG1312 B10A User s Guide 352 ...
Страница 368: ...Appendix G Legal Information VMG1312 B10A User s Guide 368 ...
Страница 376: ...VMG1312 B10A User s Guide 376 Index ...
Страница 377: ...Index VMG1312 B10A User s Guide 377 ...
Страница 378: ...VMG1312 B10A User s Guide 378 Index ...