Premarking and remarking your traffic, Cos to egress queue premarking – Allied Telesis AlliedWare Plus Operating System Version 5.4.4C (x310-26FT,x310-26FP,x310-50FT,x310-50FP) User Manual
Page 984
Quality of Service (QoS) Introduction
Software Reference for x310 Series Switches
38.12
AlliedWare Plus
TM
Operating System - Version 5.4.4C
C613-50046-01 REV A
Premarking and Remarking Your Traffic
Premarking relates to adding QoS markers to your incoming data traffic before it is
metered (policed). Remarking is the same process when applied after metering. Network
switches will often be configured with two different premarking profiles, one for the QoS
edge switches and another for the QoS core switches. This situation would apply if you are
operating DSCP domains.
QoS markers can be applied at both the link layer (within the CoS field), and at the
network layer (within the DSCP field). For more information on this topic see
.
For boundary QoS
switches
Traffic entering QoS boundary switches is unlikely to contain pre-existing QoS tagging. In
this case, you can apply one or more of the following QoS mapping options.
■
Assign a CoS tag to data associated with a particular class-map.
■
Use the
command to enable the mls qos map premark DSCP map. This
map enables you to change the DSCP tag and also map the tag to an egress port
queue, a CoS value, or both. At the premarking stage you can set this mapping using
the command
. After policing, you can then use the
command to change the DCSP based on the packet’s bandwidth class,
or remap the existing bandwidth class, to a new value.
For an untagged packet, if no other mapping is applied and the packet is untagged, (i.e. in
the absence of any other queue selection) traffic will be sent to queue 2.
For core
QoS switches
Traffic entering ports within the QoS core network will almost certainly contain some
pre-existing QoS tagging. Where this is the case, you can apply one of the following QoS
mapping options.
■
Map the CoS tag to an egress queue. You can do this either for the whole switch or for
specific ports via their assigned policy-maps. See
■
Map the DSCP tag to an output queue. You can do this either for the whole switch or
for specific ports via their assigned policy-maps.
■
Remap incoming data DSCP or CoS tags to values that are more appropriate for a
particular switch or network.
■
Assign bandwidth classes for your packets, based on the incoming DSCP. See
to egress queue premarking commands” on page 38.14
CoS to egress queue premarking
If you are using CoS tagging for your QoS functions, your traffic is likely to be either
entering the switch with a pre-existing CoS tag, or will have appropriate 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. There are two
fundamental methods of applying CoS tagged packets to egress queues:
1.
Apply a global mapping of CoS tags to egress queues for all ports.
2.
Apply a CoS to egress queue mapping for the class-map / policy-map. 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. Note that this procedure takes priority over that
described in method (1) above.
These methods and their related commands will be now be described in greater detail.