Qos And Filters - Avaya 8800 Planning And Engineering, Network Design

QoS design guidelines

QoS and filters

Filters help you provide QoS by permitting or dropping traffic based on the parameters you
configure. You can use filters to mark packets for specific treatment.
Typically, filters act as firewalls or are used for Layer 3 redirection. In more advanced cases, traffic
filters can identify Layer 3 and Layer 4 traffic streams. The filters cause the streams to be remarked
and classified to attain a specific QoS level at both Layer 2 (802.1p) and Layer 3 (DSCP).
Traffic filtering is a key QoS feature. The Avaya Ethernet Routing Switch 8800/8600, by default,
determines incoming packet 802.1p or DiffServ markings, and forwards traffic based on their
assigned QoS levels. However, situations exist where the markings are incorrect, or the originating
user application does not have 802.1p or DiffServ marking capabilities. Also, the administrator may
want to give a higher priority to select users (executive class). In any of these situations, use filters
to prioritize specific traffic streams.
You can use Advanced filters to assign QoS levels to devices and applications. To help you decide
whether or not to use a filter, key questions include:
1. Does the user or application have the ability to mark QoS information on data packets?
2. Is the traffic source trusted? Are the QoS levels set appropriately for each data source?
Users may maliciously set QoS levels on their devices to take advantage of higher priority
levels.
3. Do you want to prioritize traffic streams?
This decision-making process is outlined in the following figure.
Figure 147: Filter decision-making process
Advanced filters
Advanced filters are provided through the use of Access Control Templates (ACT), Access Control
Lists (ACL), and Access Control Entries (ACE), which are implemented in software.
June 2016 Planning and Engineering — Network Design
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