Cisco Catalyst 3750 - Queueing and Scheduling of Hierarchical Queues

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Catalyst 3750 Metro Switch Software Configuration Guide
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Chapter 26 Configuring QoS
Understanding Hierarchical QoS
Queueing and Scheduling of Hierarchical Queues
Figure 26-11 shows the egress queueing and scheduling flowchart for a hierarchical queue.
Figure 26-11 Egress Queueing and Scheduling Flowchart for a Hierarchical Queue
98885
Receive packet from
egress queue-set
and scheduling.
Read QoS label (DSCP,
CoS, IP precedence,
or MPLS EXP bits).
Determine egress queue
and thresholds based on
the label, VLAN ID, or both.
Are thresholds
being exceeded?
Send the packet
out the ES port.
Queue the packet.
Service the queue
according to the
CBWFQ, LLQ, or both.
Drop packet.
Start
Done
Ye s
No
Rewrite any or all DSCP,
IP precedence,
MPLS EXP, and
CoS bits as appropriate.