Cisco IE 3000 Software Configuration Manual page 583

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Configuring QoS

Receive packet from

(DSCP or CoS value).

Determine egress queue

number and threshold

based on the label.

being exceeded?

Queue the packet. Service

the queue according to

the SRR weights.

Rewrite DSCP and/or

Each port supports four egress queues, one of which (queue 1) can be the egress expedite queue.These

queues are configured by a queue-set. All traffic leaving an egress port flows through one of these four

queues and is subjected to a threshold based on the QoS label assigned to the packet.

the reserved pool. The switch uses a buffer allocation scheme to reserve a minimum amount of buffers

for each egress queue, to prevent any queue or port from consuming all the buffers and depriving other

queues, and to control whether to grant buffer space to a requesting queue. The switch detects whether

the target queue has not consumed more buffers than its reserved amount (under-limit), whether it has

consumed all of its maximum buffers (over limit), and whether the common pool is empty (no free

Queueing and Scheduling Flowchart for Egress Ports

the internal ring.

Read QoS label

Are thresholds

CoS value as

appropriate.

Send the packet

out the port.

shows the egress queue buffer. The buffer space is divided between the common pool and

Drop packet.

Cisco IE 3000 Switch Software Configuration Guide

Understanding QoS

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