Quality of Service Overview

QoS is all about managing the bandwidth in a manner that aligns the delivery characteristics of a given flow with the available port resources. In a QoS context, a flow is a stream of IP packets that are classified with the same class of service as it transits the interface. QoS manages bandwidth for each flow by taking advantage of its ability to:

• Assign different priority levels to different packet flows
• Mark or re-mark the packet priority at port ingress with a Type of Service
• Sort flows by transit queue such that a higher priority queue gets preferential access to bandwidth during packet forwarding
• Limit the amount of bandwidth available to a given flow by either dropping (rate limiting) or buffering (rate shaping) packets in excess of configured limits

These QoS abilities collectively make up a Class of Service (CoS). The remainder of this section will briefly describe CoS and its components.