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WFQ (Weighted Fair Queuing):

Weighted Fair Queuing is a queuing algorithm that combines

fair queuing and preferential weighting. The fairness aspect

of WFQ functions similarly to round-robin queuing, withqueues serviced in a continuously repeating sequence from

top to bottom, and then starting at the top again. The

weighting aspect of WFQ applies a "weight" to a queue thatindicates the importance of the queue in relation to theavailable resources. The weight is used to ensure that more

important queues get serviced more often than other less

important queues. With WFQ, queues are first sorted inorder of their increasing weighted value. Then, each queue is serviced in order of its

weighted proportion to the available resources.

Weighted fair queuing (WFQ) is a method of automatically smoothing out the flow ofdata in packet-switched communication networks by sorting packets to minimize the

average latency and prevent exaggerated discrepancies between the transmission

efficiency afforded to narrowband versus broadband signals. In WFQ, the prioritygiven to network traffic is inversely proportional to the signal bandwidth. Thus,

narrowband signals are passed along first, and broadband signals are buffered.

WFQ has little or no effect on the speed at which narrowband signals are transmitted,but tends to slow down the transmission of broadband signals, especially during times

of peak network traffic. Broadband signals share the resources that remain after low-

bandwidth signals have been transmitted. The resource sharing is done according toassigned weights. In flow-based WFQ, also called standard WFQ, packets are classified

into flows according to one of four criteria: the source Internet Protocol address (IP

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address), the destination IP address, the source Transmission Control Protocol (TCP)or User Datagram Protocol (UDP) port, or the destination TCP or UDP port. Each flow

receives an equal allocation of network bandwidth, hence the term fair.

Priority Queuing is the oldest of the queuing techniques. Traffic is prioritized with a

priority-list, applied to an interface with a priority-group command. The traffic goes

into one of four queues: high, medium, normal, or low priority. When the router isready to transmit a packet, it searches the high queue for a packet. If there is one, itgets sent. If not, the medium queue is checked. If there is a packet, it is sent. If not,

the normal, and finally the low priority queues are checked. For the next packet, theprocess repeats. If there is enough traffic in the high queue, the other queues may get

starved: they never get serviced.

WFQ can prevent high-bandwidth traffic from overwhelming the resources of a

network, a phenomenon which can cause partial or complete failure of low-bandwidthcommunications during periods of high traffic in poorly managed networks.

This can be seen as a combination of priority queuing and fair queuing. All queues are

serviced so that none are starved, but some queues are serviced more than others. Aweight is applied to queues to give some queues higher priority. For example, one

queue may get half the available bandwidth and other queues will get an allocation of

the remaining bandwidth. Traffic may be prioritized according to packet markings,source and destination IP address fields, port numbers, and information in the ToS

field. WFQ weights traffic so that low-bandwidth traffic gets a fair level of priority. Ifhigh-priority queues are not in use, lower-priority traffic uses its queues. This

prevents high-bandwidth traffic from grabbing an unfair share of resources.

Dax Product Offering: Some of the Dax the product that supports WFQ (WeightedFair Queuing) is as follows:

DX-800XE series:http://www.daxnetworks.com/Products/Routers/Dax%20DX-80XE%20series.asp

DX-1721:http://www.daxnetworks.com/Products/Routers/Dax DX-1721.asp






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