Home > Articles > Quality of Service Design Overview

Quality of Service Design Overview

Chapter Description

This chapter provides an overview of the QoS design and deployment process. This process requires business-level objectives of the QoS implementation to be defined clearly and for the service-level requirements of applications to be assigned preferential or deferential treatment so that they can be analyzed.

Scavenger Class

When addressing the QoS treatment of Scavenger traffic, the following guidelines are recommended:

  • Scavenger traffic should be marked to DSCP CS1.

  • Scavenger traffic should be assigned the lowest configurable queuing service; for instance, in Cisco IOS, this means assigning a CBWFQ of 1 percent to Scavenger.

The Scavenger class is intended to provide deferential services, or less-than best-effort services, to certain applications. Applications assigned to this class have little or no contribution to the organizational objectives of the enterprise and are typically entertainment oriented in nature. These include peer-to-peer media-sharing applications (KaZaa, Morpheus, Groekster, Napster, iMesh, and so on), gaming applications (Doom, Quake, Unreal Tournament, and so on), and any entertainment video applications.

Assigning Scavenger traffic to minimal bandwidth queue forces it to be squelched to virtually nothing during periods of congestion, but it allows it to be available if bandwidth is not being used for business purposes, such as might occur during off-peak hours.

The Scavenger class is a critical component to the DoS and worm mitigation strategy, discussed next.

6. DoS and Worm Mitigation Strategy Through Scavenger Class QoS | Next Section Previous Section