Brocade Multi-Service IronWare QoS and Traffic Management Configuration Guide (Supporting R05.6.00) - Manual (Page 137)

Multi-Service IronWare QoS and Traffic Management Configuration Guide 123
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Configuring packet drop priority using WRED
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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 Brocade devices. They are
numbered 0 to 7.
The drop-precedence-value variable for the drop-precedence parameter is the TOS or 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. Use the % sign after you
type the drop-probability-max value. The default values are shown in
Table 31 .
Setting the minimum and maximum average queue size
Configuration Considerations
When setting the minimum and maximum average queue size, consider the following
• If a user enters a min-avg-queue-size that is equal to what is currently configured for the
max-avg-queue-size, then the min-avg-queue-size is decremented by 64. The
min-avg-queue-size is decremented by 64 because the value must be different from the
max-avg-queue-size that is currently configured. The following example is a warning message
that is displayed on the console.
Warning: The min-avg-queue-size is decreased to(min-avq-queue-size-64)as min and
max should be different to be effective.
• If a user enters a max-avg-queue-size that is equal to what is currently configured for the
min-avg-queue-size, then the max-avg-queue-size is incremented by 64. The
max-avg-queue-size is incremented by 64 because the value must be different from the
min-avg-queue-size that is currently configured. The following example is a warning message
that is displayed on the console.
Warning: The max-avg-queue-size is increased to(max-avq-queue-size+64)as min and
max should be different to be effective.
• If a user enters a min-avg-queue-size equal to the max-avg-queue-size, then the
max-avg-queue-size is incremented by 64. The max-avg-queue-size is incremented by 64
because the value must be different from the min-avg-queue-size The following example is a
warning message that is displayed on the console.
Warning: The max-avg-queue-size is increased to(max-avq-queue-size+64)as min and
max should be different to be effective.
However if a user enters a max-avg-queue-size and min-avg-queue-size equal to 32768, then the
min-avg-queue-size is decremented.
To set the maximum average queue size for queue type 1 and drop precedence 0 to the maximum
size of 32768 Kbytes, use the following command.
Brocade(config)#qos queue-type 1 wred drop-precedence 0 max-avg-queue-size 32768
Syntax: [no] qos queue-type queue-type wred drop-precedence drop-precedence-value
max-avg-queue-size max-size
To set the minimum average queue size to the maximum size of 16 Kbytes, use the following
command.