Low latency queuing

© 2004 Cisco Systems, Inc. All rights reserved. bcran v2.1—10-13

A protocol-dependent switching process handles traffic arriving at a router interface. The switching process includes delivery of traffic to an outgoing interface buffer.

FIFO queuing is the classic algorithm for packet transmission. With FIFO, transmission occurs in the same order as messages are received. Until recently, FIFO queuing was the default for all router interfaces. If users require traffic to be ordered differently, they must establish a queuing policy other than FIFO queuing.

In addition to FIFO, Cisco IOS software offers other alternative queuing options:

■ Weighted fair queuing (WFQ): Prioritizes interactive traffic over file transfers to ensure satisfactory response time for common user applications. WFQ can prioritize traffic based on flows (flow-based WFQ) or user-defined classes (class-based WFQ [CBWFQ]).

■ Class-based weighted fair queuing (CBWFQ) (Cisco IOS Release 12.2)

■ Low latency queuing (LLQ) (Cisco IOS Release 12.2)

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