Dell Brocade DCX, Configuration Manual

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478 BigIron RX Series Configuration Guide
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Configuring packet drop priority using WRED
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The <queue-number> variable is the number of the forwarding queue that you want to enable
WRED for. There are four forwarding queues on device. They are numbered 0 to 3 with zero as the
lowest priority queue and three the highest.
Setting the averaging-weight (Wq) parameter
The Wq parameter is configured as the averaging-weight parameter. In this implementation, you
can set one of 13 (1 - 13) possible values. These values represent a Wq value as described in
Table 92
To set the wq parameter for queues with a queue type of 1 to 25%, use the following command.
BigIron RX(config)#qos queue-type 1 wred averaging-weight 25%
This gives the current queue size a weight of 25% over the statistical average queue size.
Syntax: [no] qos queue-type <queue-type> wred averaging-weight <avg-weight-value>
The <queue-type> variable is the number of the forwarding queue type that you want to configure
the averaging-weight (Wq) parameter for. There are eight forwarding queue types on device
Routers. They are numbered 0 to 3.
The <avg-weight-value> variable is the weight-ratio between instantaneous and average queue
sizes. It can be one of the 13 values expressed as 1 to 13 described in Table 92 . The default value
is 9 which maps to a Wq value of.19%.
Configuring the drop precedence parameters
The DSCP/TOS bits in packets are used to prioritize packet delivery for specified queue types.
These values are from 0 to 3. Packets with a DSCP/TOS value of 0 are least likely to be dropped
and packets with a DSCP/TOS of 3 are most likely to be dropped.
TABLE 92
Possible Wq values
Averaging weight
setting Wq value as a percentage
1 50%
2 25%
3 12.5%
4 6.2%
5 3.12%
6 1.56%
7 0.78%
8 0.4%
9 0.2%
10 0.09%
11 0.05%
12 0.02%
13 0.01%