Specifications

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Figure 22. SRR compared to WRR
The shaper is implemented on a per queue basis and has the effect of smoothing transient bursts of data that pass
through that port. SRR will limit traffic output for that queue to the stated rate. Even if bandwidth is available, the rate
will never exceed what is configured. SRR also modifies the way in which it schedules data when compared to the
WRR algorithm. This can be seen in the diagram above which shows a representation of the packet scheduling
order for both algorithms.
6.5.5. Strict Priority Queuing
Selected linecards in the Catalyst 6500 family support a strict priority queue on a per port basis. This queue operates
outside of the bounds set by the Round Robin scheduling algorithm described above. The purpose of a strict priority
queue is to facilitate support for latency sensitive traffic that gets queued on the linecard. When a packet is placed
into a strict priority queue, scheduling of packets from WRR queues will cease and the packet(s) in the strict priority
queue will be transmitted. Only when the strict priority queue is empty will the scheduling process recommence
sending packets from WRR queues.
Figure 23. Strict Priority Queuing process