Allied Telesis x900-24 series manual Combining hardware filters and QoS, Filter rules table

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Combining hardware filters and QoS

Combining hardware filters and QoS

The switch compares the packet with every hardware filter before it compares the packet with any QoS flow group. If the packet matches a hardware filter, the switch takes the action specified by that hardware filter and stops the comparison process. If a packet matches both a hardware filter and a QoS flow group, the packet only gets matched against the hardware filter. It bypasses the QoS process.

If the hardware filter actions include discard, then this is not a problem, because the packet was never going to get into the QoS system anyway (given that it was being discarded). But, if the hardware filter actions include forward, and the packet would also be matched by a QoS flow group, then this is a problem. The packet will not be matched by the QoS flow group, so the switch will not apply any intended QoS-based filtering, metering, queue redirection, etc to the packet. Instead the switch will forward the packet as if it belongs to the default traffic class for the port’s QoS policy.

For this reason, we only recommend combining hardware filters and QoS if all your hardware filters result in traffic being dropped. For traffic that you want forwarded with QoS control, use QoS for both the filtering and the QoS functionality. Of course, you can also use QoS flow groups to drop traffic.

How many filters can you create?

The total number of filters that can be created is not an exact number, but depends on which fields the various filters are matching on. So, to understand how to work out whether the set of filters you are creating might run out of space, it is necessary to understand the way in which the filters operate in the switch hardware.

There are two items within the switch hardware which set limits on the number of filters that can be created: the filter rules table and the profile (mask).

Hardware filters and QoS share the same filter rules table and mask.

1. The filter rules table

One item that sets a limit on the number of filters is the table that contains the list of filter rules. This has a strict limit of 1024 entries. Entries get made when:

zYou create a hardware filter.

zYou use QoS to apply a classifier to a port.

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Contents Introduction AlliedWareTM OSThis document contains the following What information will you find in this document?Creating dedicated hardware filters Configuring packet classification1st tag Configuring inner parameters for nested VLANsCore port 1st tag 2nd tag Nested VLANs disabled Customer portCreating hardware filters Then, enter the following commandFor example, imagine you have the following set of filters Effects of the action parameters Logic of the operation of the hardware filtersHow many filters can you create? Combining hardware filters and QoSFilter rules table Rule Empty Rule table Extra rules used when combining QoS and hardware filtersFollowing figure shows the copies of these rules Profile maskRule Are there enough bytes for your set of filters? Some protocols also use filters, so use some of the length Disabled by defaultOkay length For example, this set of filters would work How to see the current filter resource usage on the switch 07D0 in hexadecimal Appendix a How to use the layer 4 mask in classifiersDefault mask BinaryPoints to remember Example 1 portsExample 3 ports Example 2 portsNow it is really easy to write the classifiers 024 128256 51265536 Following table shows the port ranges for the largest blocksC613-16058-00 REV C
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