Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) - Manual (Page 986)

Quality of Service (QoS) Introduction
Software Reference for x310 Series Switches
38.14 AlliedWare Plus TM Operating System - Version 5.4.4C C613-50046-01 REV A
CoS settings for VCStack stack operation
In general you can apply the same principles when configuring QoS on a VCStack as you
would for single switch; however there are a few specific changes that you will need to
make.
Switches within a VCStack exchange their stack management information and user data
over their high speed inter-stacking links. The stack management information is pre-
assigned to the egress queue 7. This is the highest value queue, and (in a stacked
configuration) its traffic should not be shared with any user data. However, any CoS
tagging of 7 applied to the incoming data will automatically be assigned to queue 7 as it
crosses the internal stacking links. You will therefore need to reconfigure your CoS to
Queue settings to ensure that no user data is sent to queue 7.
To prevent this from happening, we recommend that you make appropriate changes to
your queue settings (mappings) to reflect the stacking requirement previously described.
For more information on this topic, see
“Mapping CoS tags to traffic types” on
page 38.13 .
This process should include (but not be limited to) running the following command to
ensure that any remaining user still carrying a CoS 7 tag will be mapped to egress queue 6.
To remap priority CoS traffic to egress queue 6, run the following command.
DSCP to egress queue premarking
If you are using DSCP tagging for your QoS functions, your traffic is likely to be entering
the switch either with a pre-existing DSCP tag, or will have appropriate DSCP tags
attached via your class-maps and policy-maps. You can now mark the data for a particular
egress queue, which will take effect when the data reaches its output port.
If your switch forms part of a DSCP domain, you can adapt the steps in this section to
apply the mappings and settings to match the standards you have selected for the
domain. This mapping - which forms part of the policy-map - is applied at an input port,
but will take effect at the packet’s destination output port.
DSCP to egress queue premarking commands
A number of commands can be used for mapping DSCP tags. Where these conflict, the
switch applies a pre-defined set of priorities.
Table 38-5 lists these priorities in order
(lowest priority first).
Where a packet that contains both CoS and a DSCP fields and each field maps to a
different class-map / policy-map, the switch will apply a priority based on the creation
date of class-maps - the earlier the creation date, the higher the priority priorities.
awplus# config terminal
awplus(config)# mls qos map cos-queue 7 to 6
Table 38-5: DSCP Mapping Commands in Hierarchical Order
Command Function
trust dscp Setting the trust dscp enables the
mls qos map premark-dscp to command to apply.
See, “Setting the Trust DSCP Map” on page 38.15 .
mls qos map premark-
dscp to With the trust dscp set, this command applies a
remapping table whose values include the dscp and
egress queues.