User guide

Summit24e3 Switch Installation and User Guide 133
12 Quality of Service (QoS)
This chapter covers the following topics:
• Overview of Policy-Based Quality of Service on page 133
• Applications and Types of QoS on page 134
• Configuring QoS for a Port or VLAN on page135
• Traffic Groupings on page 136
— MAC-Based Traffic Groupings on page 137
— Explicit Class of Service (802.1p and DiffServ) Traffic Groupings on page 138
— Physical and Logical Groupings on page 142
• Verifying Configuration and Performance on page 143
• Modifying a QoS Configuration on page 144
• Traffic Rate-Limiting on page 144
• Dynamic Link Context System on page 144
Policy-based Quality of Service (QoS) is a feature of ExtremeWare and the Extreme 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
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 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 can be programmed by ExtremeWare with bandwidth limitation
and prioritization parameters. The bandwidth limitation 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.
Summit24e3 switches support up to four physical queues per port.