Weighted fair queuing (WFQ) is another queuing technique, and is the default used on router interfaces with less that 2.048 Mbps of bandwidth. Weighted fair queuing is concerned with ensuring that all traffic flows receive predictable bandwidth to meet their needs. For example, it will place smaller, interactive traffic (like telnet) at the front of a queue. Traffic is placed in the queue according to when the last bit is received, rather than the first. This helps to ensure that larger packets do not interfere with smaller packets, starving them of bandwidth.
Traffic is classified according to a number of factors before being placed in a queue. For example, WFQ is aware of quality of service (QoS) techniques like IP Precedence. This allows it to characterize traffic according to its packet-defined priority, and ensure that it is allocated an acceptable level of bandwidth. By the same token, on Frame Relay interfaces, WFQ will take into account diagnostic messages like FECN, BECN, and the discard eligibility (DE) of frames.