Users Guide

1512 Class-of-Service
• TCP packets with rates higher than the PIR/PBS or which belong to
neither class CoS 1 or class CoS 2 violate the rate (red). These packets
will be dropped randomly at an increasing rate between 0 and 10%
when the outgoing interface is congested between 50 and 100%.
• Non-TCP packets in CoS queue 0 or 1 will be dropped randomly at an
increasing rate between 0 and 15% when the outgoing interface is
congested between 50 and 100%.
console(config-policy-classmap)#police-two-rate 800 96 950 128
conform-action transmit exceed-action transmit violate-action
transmit
console(config-policy-classmap)#conform-color cos1 exceed-
color cos0
console(config-policy-classmap)#exit
console(config-policy-map)#exit
9 Enable WRED drop on traffic classes 0 and 1.
console(config)#cos-queue random-detect 0 1
10 Set the exponential-weighting-constant. The exponential weighting
constant smooths the result of the average queue depth calculation by the
following function:
average depth = (previous queue depth * (1-1/2^n)) + (current queue
depth * 1/2^n).
The average depth is used in calculating the amount of congestion on a
queue. Because the instantaneous queue depth fluctuates rapidly, larger
values of the weighting constant cause the average queue depth value to
respond to changes more slowly than smaller values.
console(config)#random-detect exponential-weighting-constant 4
11 Configure the queue parameters for traffic class 0 and 1. We set the
minimum threshold and maximum thresholds to 80–100% for green
traffic, 70–100% for yellow traffic, and 50–100% for red traffic. Non-TCP
traffic drops in the 50–100% congestion range. Green traffic is dropped at
a very low rate to slowly close the TCP window. Yellow and red traffic are
dropped more aggressively.
console(config)#random-detect queue-parms 0 1 min-thresh 80 70
50 50 max-thresh 100 100 100 100 drop-prob-scale 3 5 10 15
12 Assign the color policies to ports. The metering policies are applied on
ingress ports.