Atm Traffic Classes; Traffic Parameters - ZyXEL Communications MSC1024G Series User Manual

Managment switch card

Hide thumbs Also See for MSC1024G Series:

Table of Contents

Chapter 13 Profile Screens

Traffic shaping controls outgoing (downstream) traffic, not incoming

(upstream) traffic.

13.12.1 ATM Traffic Classes

These are the basic ATM traffic classes defined by the ATM Forum Traffic Management 4.0

Specification.

13.12.1.1 Constant Bit Rate (CBR)

Constant Bit Rate (CBR) is an ATM traffic class that provides fixed bandwidth. CBR traffic is

generally time-sensitive (doesn't tolerate delay). CBR is used for connections that

continuously require a specific amount of bandwidth. Examples of connections that need CBR

would be high-resolution video and voice.

13.12.1.2 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 (rt-VBR) or

non-real time (nrt-VBR) connections.

The rt-VBR (real-time Variable Bit Rate) type is used with bursty connections that require

closely controlled delay and delay variation. An example of an rt-VBR 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 nrt-VBR (non real-time Variable Bit Rate) type is used with bursty connections that do not

require closely controlled delay and delay variation. An example of an nrt-VBR connection

would be non-time sensitive data file transfers.

13.12.1.3 Unspecified Bit Rate (UBR)

The Unspecified Bit Rate (UBR) ATM traffic class is similar to the ABR traffic class for

bursty data transfers. However, while ABR gives subscribers a set amount of bandwidth, UBR

doesn't guarantee any bandwidth and only delivers traffic when the network has spare

These are the parameters that control the flow of ATM traffic.

13.12.2.1 Peak Cell Rate (PCR)

Peak Cell Rate (PCR) is the maximum rate at which the sender can send cells. This parameter

may be lower (but not higher) than the maximum line speed. 1 ATM cell is 53 bytes (424 bits),

so a maximum speed of 832Kbps gives a maximum PCR of 1962 cells/sec. This rate is not

guaranteed because it is dependent on the line speed.

MSC1000G/1024G/1224G Series User's Guide

Msc1224g series Msc1000g series