Specifications

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This command example above sets the transmit queue size ratio on a 1P3Q8T port setting queue #1 and queue #2

to having 30% each of the allocated buffer space. Queue #3 is set to using 20% of the allocated buffer space. The

most obvious question that springs to mind is why the percentages in this example don’t add up to 100%. The

reason the allocated amount not adding up to 100% is due to the presence of the strict priority queue. This

command does not allow the direct allocation of buffer space to the strict priority queue. Rather, the allocated

amount given to the high priority queue is assigned to the strict priority queue. In this example, the high priority

queue has been allocated 20% of the buffer space, so the strict priority queue will also be allocated the same

amount. When this is factored into the equation, the sum of the weights now adds up to 100% (20+20+30+30).

8. Configuring QoS on the Policy Feature Card

The following section provides a guide to the configuration of QoS features on the PFC. The QoS elements that can

be configured include Policing (also referred to as Rate Limiting) and Classification using Access Control Lists.

8.1 Classification and Policing with the PFC

The PFC supports the classification and the policing of frames. Classification can use an ACL to assign (mark) an

incoming frame with a priority (DSCP). Policing allows a stream of traffic to be limited to a certain amount of

bandwidth.

The processing path through the PFC3 is shown in the following diagram.

Figure 31. QoS Processing for the PFC3