Allied Telesis AlliedWare Plus 5.2.1, Руководство по программному обеспечению

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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 39.13
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 39-5 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.
Table 39-5: DSCP Mapping Commands in Hierarchical Order
Table 39-5 shows that if no overriding commands have been configured, and there is no CoS
value in the packet, then the default setting of the mls qos queue command will send all data
out via its port’s egress queue 2. You can use the mls qos queue command to reset the egress
queue for each port on the switch. If the packet does contain a CoS tag value, then this queue
will be that shown in the mapping in the section
“Mapping CoS tags to traffic types” on
page 39.12 .
Command Function
mls qos map policed-dscp to This remarking function can remap previously set dscp
values and queue selections.
trust dscp Setting the trust dscp enables the mls qos map mark-dscp
to command to apply. See, “Setting the Trust DSCP Map”
on page 39.14 .
set dscp With the trust dscp set, this command will change the dscp
value in the packet.
mls qos map mark-dscp to With the trust dscp set, this command applies a remapping
table whose values include the dscp and egress queues.
mls qos queue Sets a default egress queue for each individual port (or
range of ports) on the switch.