Inside Cisco IOS Software Architecture (CCIE Professional Development)

QoS Overview

Consider a basic network of two computers connected by a single link. In a perfect world, these computers could send and receive as much data as they want without worrying about transit delay; the only thing bounding the number of file transfers, voice calls, and video sessions between them is the processing power of the systems themselves. They have a dedicated link with infinite bandwidth!

Real networks consist of shared links with limited bandwidth and some (measurable) amount of delay. Networks able to handle the full output rate of every connected node are rarely economical; instead, network designers attempt to balance costs with the average and peak rates of traffic they expect. Devices within the network, such as routers, ...