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How do Weighted Fair Queueing (WFQ) and Class Based Weighted Fair Queueing (CBWFQ) operate?

April 26, 2017based cbwfq class fair operate queueing weighted wfq

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How do Weighted Fair Queueing (WFQ) and Class Based Weighted Fair Queueing (CBWFQ) operate?

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A. Fair queueing seeks to allocate a fair share of an interface’s bandwidth among active conversations or IP flows. It classifies packets into subqueues, identified by a conversation identification number, using a hashing algorithm based on several fields of the IP header and the length of the packet. The following is how the weight is calculated: • W=K/(precedence +1) K= 4096 with Cisco IOS 12.0(4)T and earlier releases, and 32384 with 12.0(5)T and later releases. The lower the weight, the higher the priority and the share of the bandwidth. In addition to the weight, the length of the packet is taken into account. CBWFQ allows you to define a class of traffic and assign it a minimum bandwidth guarantee. The algorithm behind this mechanism is WFQ, which explains the name. To configure CBWFQ, you define specific classes in map-class statements. Then you assign a policy to each class in a policy-map. This policy-map will then be attached outbound to an interface.