Extreme Networks BlackDiamond 6800 Installation And User Manual page 81

Configuring QoS Functions
Enabling and Disabling RED on ATM Ports
The existing ExtremeWare commands to enable and disable RED ports have been
enhanced to provide RED configuration attributes for the ATM module. Because the
ATM module supports eight egress queues per port, the commands were enhanced to
allow the user a way to enable RED selectively on an individual port and queue basis.
By default, RED is disabled.
To enable RED on a specified ATM port, use the following command:
enable red ports <portlist> {queue <queue#>}
To disable RED on a specified ATM port, use the following command:
disable red ports <portlist> {queue <queue#>}
The optional keyword applies only to ATM ports. You can use this keyword to
queue
enable or disable the RED function on an individual queue basis.
The parameter is an integer in the range from 0 to 7, and identifies one of the
queue#
eight egress queues. If you omit the keyword, the command applies to all of the
queue
queues for the ATM port.
Configuring the RED Minimum Queue Length Threshold
The packet drop probability is based, in part, on the RED minimum queue length
threshold. When the average queue length exceeds this threshold, the RED algorithm is
activated and begins dropping packets. The packet drop rate increases in a linear
fashion as the average queue length increases or until the average queue length hits the
maximum threshold.
This command applies only to PoS and ATM ports.
To configure the minimum queue length threshold for RED operation on a specified
ATM port, use the following command:
config red min-threshold <percent> ports <portlist>
The threshold value is specified as a percentage in the range from 1 to 100. For ATM
ports, the minimum threshold is a percentage of 1000 packet buffers, and the maximum
threshold is set to the value calculated by the formula:
minimum ((3 * minimum threshold buffers), maximum available buffers)
Asynchronous Transfer Mode (ATM) Module Installation and User Guide 3-39