Priority Queuing; Atm Module Overview - 3Com 3C63100-AC-C - PathBuilder S600 Bridge/router Reference Manual

ATM Module
Overview
Generates the backplane timing 8KHZ clock and generates ATM bus timing
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Accepts an 8kHZ signal from all modules together with a 1.544MHz external
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BITs Clock

Priority Queuing

The PathBuilder S600 with STX provides separate cell buffer queues per virtual
interface. You can assign multiple VCs to each virtual interface and map them to
the desired queue. The STX services the queues in order: queue 0, then queue 1,
then queue 2 and queue 3. Figure 44 illustrates this priority queuing.
If the STX finds data in a higher queue while it is servicing another queue, it
services the higher queue, thereby maintaining the priority. For example, if the STX
finds data in queue 0 while it is servicing queue 2, the STX services queue 0. By
queuing the VCs in this way, the STX ensures that the Class of Service is
maintained.
The ensuing traffic from the queues is then shaped according to the traffic
shaping parameter that you set (64Kbps to 155 Mbps) in cells per second. In
addition, each circuit can be policed based on the congestion threshold that you
set for each of the queues. You can also specify the actions that you want to be
taken if a queue is found to be congested based on the threshold you have set.
Figure 44 PathBuilder S600 with STX Priority Queuing
Physical
Port
Cell Bus
The PathBuilder S600 supports the following application modules with ATM
interfaces:
DS3 UNI
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E3 UNI
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OC3/STM-1 UNI
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DS1 UNI with IMA
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E1 UNI with IMA
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"Virtual
Interfaces"
1
2
3
.
.
.
.
.
.
.
.
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ATM Module Overview

CBR
VBR
Q0 = 500 cell buffer
Traffic
Q1 = 1500 cell buffer
Shaper
Q2 = 3000 cell buffer
Q3 = 3000 cell buffer
Queue Controller
Cell buffers
77