20-12
Catalyst 3550 Multilayer Switch Software Configuration Guide
78-11194-03
Chapter 20 Configuring QoS
Understanding QoS
Queueing and Scheduling
After a packet is policed and marked, the queueing and scheduling process begins as described in these
sections:
•
Queueing and Scheduling on Gigabit-Capable Ports, page 20-12
•
Queueing and Scheduling on 10/100 Ethernet Ports, page 20-15
Queueing and Scheduling on Gigabit-Capable Ports
Figure 20-5
shows the queueing and scheduling flowchart for Gigabit-capable Ethernet ports.
Figure 20-5 Queueing and Scheduling Flowchart for Gigabit-Capable Ethernet Ports
Note
If the expedite queue is enabled, WRR services it until it is empty before servicing the other three
queues.
46978
T1 and T2 thresholds
Queue size
Queue number
No
Yes
Read CoS value and the
CoS-to-queue map.
Determine high and low
threshold of the queue,
and determine the queue size.
Are thresholds
being exceeded?
Put packet in the specified
queue and service the
queue according to WRR.
Determine which DSCPs are
mapped to each threshold.
Read the DSCP-to-threshold
map.
Drop packet.
Start
Done