Dell PowerConnect B-RX Configuration Manual page 568

18
Configuring packet drop priority using WRED
The <queue-type> variable is the number of the forwarding queue type that you want to configure
drop-precedence for. There are eight forwarding queue types on BigIron RX Routers. They are
numbered 0 to 3.
The <drop-precedence-value> variable for the drop-precedence parameter is the TOS/DSCP value
in the IPv4 or IPv6 packet header. It determines drop precedence on a scale from 0 - 3. Packets
than contain a DSCP value of 0 are least likely to be dropped and packets with a value of 3 are
most likely to be dropped. The default value is 0.
The <min-size> variable is the average queue size below which all packets are accepted. Possible
values are 1 - 32768 KBytes. It must be set in multiples of 64K. The default values are shown in
Table 97.
The <max-size> variable is the average queue size above which all packets are dropped. (1 -
32768) (KBytes) in multiples of 64K. The default values are shown in Table 97.
Setting the maximum packet size
To set the maximum drop probability for queue type 1 and drop precedence 0 when the queue size
reaches the Max-average-q-size value to 20% use the following command.
BigIron RX(config)#qos queue-type 1 wred drop-precedence 0 drop-probability-max
20%
Syntax: [no] qos queue-type <queue-type> wred drop-precedence <drop-precedence-value>
drop-probability-max <p-max%>
The <queue-type> variable is the number of the forwarding queue type that you want to configure
drop-precedence for. There are eight forwarding queue types on BigIron RX Routers. They are
numbered 0 to 3.
The <drop-precedence-value> variable for the drop-precedence parameter is the TOS/DSCP value
in the IPv4 or IPv6 packet header. It determines drop precedence on a scale from 0 - 3. Packets
than contain a DSCP value of 0 are least likely to be dropped and packets with a value of 3 are
most likely to be dropped. The default value is 0.
The <p-max> variable defines the maximum drop probability when the queue size is at the value
configured for max-avg-q-size. This value is expressed as a percentage. The default values are
shown in Table 97.
Restoring to default WRED parameters
Table 97 describes all of the default values for each of the WRED parameters. If you change any of
the values from the default values, you can restore the defaults per queue type. To reset the queue
type 1 with default values for the WRED parameters, use the following command.
BigIron RX(config)#qos queue-type 1 wred default-params
Syntax: [no] qos queue-type <queue-number> default-params
The <queue-number> variable is the number of the forwarding queue that you want to configure
drop-precedence for. There are four forwarding queues on BigIron RX Routers. They are numbered
0 to 3.
492 BigIron RX Series Configuration Guide
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