Page 27 | AlliedWare Plus™ OS: Overview of QoS
To specify the averaging factor, use the command:
awplus(config)#mls qos queue-set <1-4> [queues <list>]
averaging-factor <0-15>

Tail-drop mode

By default, ports use tail-drop mode and the default queue-set for that port type (see
"Default settings" on page 23). If you need to explicitly set a port to tail-drop mode, or if you
want to change the queue-set, use the commands:
awplus(config)#interface <interface-name>
awplus(config-if)#mls qos queue-set <1-4> taildrop
Tail-drop mode uses the same command as random-detect mode to set the maximum and
minimum thresholds for each bandwidth class:
awplus(config)#mls qos queue-set <1-4> [queues <list>] threshold
<minimum-green-threshold> <maximum-green-threshold>
<minimum-yellow-threshold> <maximum-yellow-threshold>
<minimum-red-threshold> <maximum-red-threshold>
However, when a queue-set is applied to a port for tail-drop mode, only the maximum
thresholds are used. The minimum thresholds are ignored. Any settings for averaging factor
and drop probability are also ignored.
Tail-drop mode results in the following actions:
zIf the green maximum threshold is exceeded, all packets will be dropped.
zIf the yellow maximum threshold is exceeded, all yellow and red packets will be dropped.
zIf the red maximum threshold is exceeded, all red packets will be dropped.
Scheduling
On each port, you can allocate the eight queues to the following three scheduling groups:
zpriority-queue—a group of queues that use strict priority scheduling
zwrr-group
1
—a group of queues that use weighted round robin (wrr) scheduling. Packets
are only transmitted from these queues if all queues in the priority-queue group are empty.
zwrr-group 2—a second group of queues that use weighted round robin scheduling. Packets
are only transmitted from these queues if all queues in the priority-queue group and in
the wrr-group
1
are empty.
You can also configure egress rate limits for each queue, and limit how much of the port’s
packet buffer the queue can use. This last point is particularly important because it stops low-
priority queues from using up the whole packet buffer and thereby starving high-priority
queues.
The following sections describe how to configure all these aspects of scheduling. To configure
scheduling, first enter interface configuration mode for the desired port or ports.