10-1
v1.0, June 2010
Chapter
10
Class of Service (CoS) Queuing
This section describes the Class of Service (CoS) Queue Mapping and Traffic Shaping features. In this
chapter, the following examples are provided:
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“Show classofservice Trust” on page
10-3
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“Set classofservice trust Mode” on page
10-3
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“Show classofservice ip-precedence Mapping” on page
10-5
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“Configure Cos-queue Min-bandwidth and Strict Priority Scheduler Mode” on page
10-6
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“Set CoS Trust Mode of an Interface” on page
10-8
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“Configure Traffic Shaping” on page
10-9
Each port has one or more queues for packet transmission. During configuration, you can determine the
mapping and configuration of these queues.
Based on service rate and other criteria you configure, queues provide preference to specified packets. If a
delay becomes necessary, the system holds packets until the scheduler authorizes transmission. As queues
become full, packets are dropped. Packet drop precedence indicates the packet’s sensitivity to being dropped
during times of queue congestion.
Select per interface configuration scheme:
CoS mapping, queue parameters, and queue management are configurable per interface.
Queue management is configurable per interface.
Some hardware implementations allow queue depth management using tail dropping or Weighted random
early discard (WRED).
Some hardware implementations allow queue depth management using tail dropping.
The operation of CoS Queuing involves queue mapping and queue configuration.
CoS Queue Mapping
CoS Queue Mapping uses trusted and untrusted ports.
Trusted Ports
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System takes at face value certain priority designation for arriving packets.
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Trust applies only to packets that have that trust information.
