Filter Set Essentials - Avaya ERS 45 Series Technical Configuration Manual

3.2 Filter Set Essentials

At the most basic level, a filter set is a collection of policies that are identified as a single, named unit.
Each policy references classifier and action criteria for identifying and processing traffic. The policies
within a set are ordered, meaning that they are applied to ingress traffic in a specific order. This
evaluation order is important because, once a policy "hit" occurs (i.e., traffic matching the policy's filter
criteria is identified) and actions are initiated, policies with a higher evaluation order may not be enforced
even if they match the traffic being processed.
A filter set is associated with a port. The same filter set can be applied to multiple ports but can only be
applied once to any given port. When a filter set is installed, limited resources are consumed (e.g.,
filter/meter/counter resources and precedence levels/masks). If the necessary resources are not
available, the filter set installation will fail. Partial installation is not supported. Active (a.k.a. in-use) filter
sets can be modified. Classifier elements can be added and deleted, pending resource availability. In-use
filter set modification may impact traffic processing as the installed data is being updated.
Let us consider each of these items in more detail.
Filter Set Classifier Elements: a filter set classifier element identifies the protocol fields and their content
that are to be used for traffic identification. Actions to be initiated for traffic matching the specified filter
data are included as well. Elements are "named" such that all classifier elements that comprise a filter set
share the same name (i.e., the filter set name). Elements have a specific type as well (e.g., NSNA, UBP,
traffic-profile) though this is set automatically during configuration and, for the most part, is transparent to
the user. Each element also contains an evaluation order value and filter block information, if appropriate.
Filter Set Element Evaluation Order: each filter set classifier element contains an evaluation order. This
value dictates the order in which classifier elements associated with the same filter set (i.e., elements with
the same filter set name) are applied. Elements with a low evaluation order are applied before elements
with a higher evaluation order. The evaluation order can determine the actions initiated when a packet
matches multiple classifier elements in a filter set (see Table 1).
An evaluation order must be unique within a filter set. The evaluation order for a classifier block is
determined by the lowest evaluation order of the elements that are members of the block. Members of a
classifier block may be assigned the same evaluation order, though this will impact the evaluation order of
block member classifier data on platforms that honor classifier block member precedence.
Element Evaluation Order
1
2
Reason: no action conflicts – both performed (drop overrides remarking)
1
2
Reason: no action conflicts – both performed (complimentary actions)
1
2
September 2015
Action Criteria
Update DSCP: 20
Drop Packet
Update DSCP: 46
Update 802.1p: 6
Don't Drop Packet
Drop Packet
Avaya Inc. – External Distribution
avaya.com
Action Initiated
Drop Packet
Update DSCP: 46
Update 802.1p: 6
Don't Drop Packet
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