Chapter 13: Quality of Service 245
Section 13-2
â– (Optional) Use WRED receive queues:
(interface) wrr-queue random-detect min-threshold queue-id thr1-min
thr2-min ...
(interface) wrr-queue random-detect max-threshold queue-id thr1-max
thr2-max ...
For 1p2q2t, 1p3q1t, and 1p2q1t port types, WRED is used. The queue-id is
1 (standard low-priority queue) or 2 (standard high-priority queue)—except
1p3q1t ports, which add 3 (standard highest-priority queue). Two limits are
used for each of the queue thresholds: a minimum thr1-min (1 to 100 per-
cent) and a maximum thr1-max (1 to 100 percent).
When the buffer is below the minimum level, no frames are dropped. As the
buffer rises above the minimum but below the maximum, the chances that
frames will be dropped increases. Above the maximum level, all frames are
dropped.
Tip The IOS 1p3q1t and 1p2q1t transmit queues also require the wrr-queue random-
detect queue-id command to enable the WRED drop thresholds.
b. (Optional) Tune egress scheduling.
(interface) wrr-queue cos-map queue-id threshold-id cos-list
Outbound frames with certain CoS values can be mapped and sent to specific
egress queues and thresholds. The cos-list can be a single value (0 to 7), multiple
values separated by commas, or a hyphenated range of values. This mapping is
set for all switch ports (COS switch) or per-interface (IOS switch).
The port-type is the type of queuing available, as seen by the show port capa-
bilities (COS) or show queueing interface (IOS) command. The queue-id (1 for
standard or 2 for strict priority) and the threshold-id (1 to 4) identify the specif-
ic queue and threshold where outbound frames are queued. The range of values
depends on the switch port hardware.
The default mappings are shown in Table 13.6.
Displaying Information About QoS
Table 13-8 documents some switch commands that you can use to display helpful infor-
mation about QoS configuration and operation.
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