WRR QoS unused traffic classes

[Peter Koltl]

We are planning QoS for the enterprise LAN and MPLS core. At present, there are 5 traffic classes identified and no VoIP traffic. We could allocate resources and bandwidth for 5 queues and deploy such configs. But I guess it's worth defining all 8 classes and allocate queue limits and bandwidth to them. Later it will be easier to mark the new traffic and classify it into the unused queues without modifying the wrr config.

67xx 1p7q8t line card

Q3 and Q8(PQ) will not be used. 5+15% is allocated to them.

priority-queue queue-limit 15

wrr-queue queue-limit 30 15 5 10 15 5 5

wrr-queue bandwidth percent 30 15 5 10 15 5 5

I'm not sure if the allocated bandwidth and queue limit for the unused queues will affect  the existing traffic and limit the aggregated traffic quantity. Will the 5 classes be able to fill the bandwidth until there is no congestion? What happens in case of congestion? Can the traffic excess 80% or not? (For simplicity, 100% is regarded as a fraction of link capacity defined by max-reserved-bandwidth)

[Joseph W. Doherty]

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Posting

Generally, unless you're shaping or policing, bandwidth sharing commands provide a minimum bandwidth guarantee, and unused bandwidth can be used by other queues.  Also when working with more than one queue, relative ratios are usually preserved.  So, for instance, if q1 was configured for 25%, q2 for 25% and q3 for 50%, if q2 had no traffic, and q1 and q3 wanted all they could have, they would split the bandwidth 1:2 or 1/3 to 2/3.