Quality of Service (QoS)
©2008 Allied Telesis Inc. All rights reserved.
Software Version 5.2.1
AlliedWare Plus
TM
Operating System Software Reference C613-50003-00 REV E
39.21
Figure 39-9: Default Egress Queue
Egress Queue Commands Hierarchy
The destination queue that any one packet will take depends on the markers within the packet,
and the way the queueing commands have been set. Also some queueing commands will
override others. Here is how the switch prioritizes its queueing commands.
Imagine a packet entering an ingress port then traveling through the switch fabric to reach its
appropriate egress port. In this situation the following hierarchy will apply:
1.
If the packet enters an egress port carrying no QoS markers and no QoS queueing
commands have been set on the switch, then the packet will exit the port via queue
number 2.
2.
If the packet containing CoS marker arrives at an egress port, then with no other
configuration applying, then its queue mapping will be subject to the setting of the
command,
mls qos map cos-queue to
.
3.
Situations (1) and (2) can be overridden by the
mls qos queue
command. This command
sets a default queue for each switch port.
4.
If the
set queue
command has been applied to specific ports via its class-map / policy map
combination, then the queue mapping of this command will override that set by the the
mls qos queue
command for those specific ports.
5.
If the
trust dscp
then the egress queue assignment will be based on the entries in the
mls qos map, which is set by the command,
mls qos queue
. This mapping table will
override all the previous commands in this list.
6.
Finally all the above mappings may be modified by the remarker, by using the
mls qos map
policed-dscp to
QoS_EgressDefa
u
ltQ
u
e
u
e
Incomming Data
mls qos queue <0-7>
This command is applied to an ingress port
and - in the absence of other tagging - will
apply the egress queue tag selected by this
command. This example shows the
mls qos queue command set to 6.
If this command is not set, then unmarked
packets arriving at an egress port will be
sent to queue 2.
Ingress
port
Egress Queues
fabric queues
default queue
Outgoing Data
Egress
port
Q6