Cisco QoS Handbook

Quality of Service (QoS) is a suite of technologies utilized to manage bandwidth usage as data crosses computer networks.  Its most common use is for the protection of real-time and high priority data applications in converged networks. All network infrastructure devices have limits on the amount of traffic that can flow through them. In packet and frame switched networks, this results in data being delayed or dropped during times of congestion. Quality of Service (QoS) management is the collection of mechanisms that control how traffic is prioritized and handled during these times. QoS technologies, or tools, each have specific rolls that are used in conjunction with one another to build endto-end network QoS policies