Managing Congestion by Setting Packet Loss Priority for Different Traffic Flows
By default, the least significant bit of the CoS value sets the packet loss priority
(PLP) value. For example, CoS value 000 is associated with PLP low, and
CoS value 001 is associated with PLP high. In general, you can change
the PLP by configuring a behavior aggregate (BA) or multifield classifier, as discussed
in Understanding How Behavior
Aggregate Classifiers Prioritize Trusted Traffic and Overview of Assigning Service
Levels to Packets Based on Multiple Packet Header Fields.
However, on devices that do not have tricolor marking enabled, the loss priority can be configured by setting the PLP within a multifield classifier or by behavior aggregate (BA) classifier. This setting can then be used by the appropriate drop profile map and rewrite rule.
The following example shows a two-step procedure to override the default PLP settings.
The first part of this example specifies that while the DSCP code points are 110, the loss
priority is set to high; however, overriding the default PLP this
way has no effect.
Use the following procedure to configure a multifield classifier that sets the PLP.
Under the
firewallstatement, specify a name for the filter.edit user@host# edit firewall filter ef-filter
Specify the term name and match criteria you want to look for in incoming packets.
[edit firewall filter ef-filter] user@host# set term ef-multifield from precedence 6
Specify the action you want to take when a packet matches the conditions.
[edit firewall filter ef-filter] user@host# set term ef-multifield then loss-priority high forwarding-class expedited-forwarding
Verify your configuration.
[edit firewall] user@host# show
filter ef-filter { term ef-multifield { from { precedence 6; } then { loss-priority high; forwarding-class expeditd-forwarding; } } }Save your configuration.
[edit firewall] user@host# commit