ECE495 Chapter Notes - Chapter 6: Random Early Detection, Priority Queue, Tail Drop
6 Apr 2016
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Document Summary
Switch (and router) queues are susceptible to congestion. Congestion occurs when the rate of ingress traffic is greater than can be successfully processed and serialized on an egress interface. By default, if an interface"s queue buffer fills to capacity, new packets will be dropped. This condition is referred to as tail drop, and operates on a first- come, first-served basis. If a standard queue fills to capacity, any new packets are indiscriminately dropped, regardless of the packet"s classification or marking. Qos provides switches and routers with a mechanism to queue and service higher priority traffic before lower priority traffic. Queuing is covered in detail in a separate guide. Qos also provides a mechanism to drop lower priority traffic before higher priority traffic, during periods of congestion. Random early detection (wred), and is covered in detail in this guide. Random early detection (red) and weighted red (wred) Tail drop proved to be an inefficient method of congestion control.
