Specifications

ExtremeWare XOS 11.0 Concepts Guide 107
8 Quality of Service
This chapter covers the following topics:
• Overview of Policy-Based Quality of Service on page 107
• Applications and Types of QoS on page 108
• Configuring QoS on page 109
• QoS Profiles on page 110
• Traffic Groupings on page 111
• Verifying Configuration and Performance on page 120
• Guidelines for Configuring QoS on page 121
• Bi-Directional Rate Shaping on page 121
Policy-based Quality of Service (QoS) is a feature of ExtremeWare XOS and the Extreme Networks
switch architecture that allows you to specify different service levels for traffic traversing the switch.
Policy-based QoS is an effective control mechanism for networks that have heterogeneous traffic
patterns. Using Policy-based QoS, you can specify the service level that a particular traffic type receives.
Overview of Policy-Based Quality of Service
Policy-based QoS allows you to protect bandwidth for important categories of applications or to
specifically limit the bandwidth associated with less critical traffic.
For example, if voice–over-IP traffic requires a reserved amount of bandwidth to function properly,
using policy-based QoS, you can reserve sufficient bandwidth critical to this type of application. Other
applications deemed less critical can be limited so as to not consume excessive bandwidth.
The switch contains separate hardware queues on every physical port. Each hardware queue is
programmed by ExtremeWare XOS with bandwidth management and prioritization parameters. The
bandwidth management and prioritization parameters that modify the forwarding behavior of the
switch affect how the switch transmits traffic for a given hardware queue on a physical port.
The switch tracks and enforces the minimum and maximum percentage of bandwidth utilization
transmitted on every hardware queue for every port. When two or more hardware queues on the same
physical port are contending for transmission, the switch prioritizes bandwidth use so long as their
respective bandwidth management parameters are satisfied. Up to eight physical queues per port are
available.