Classes of Service Overview

In general, CoS (Class of Service) refers to a set of attributes that define the importance of a frame while it is forwarded through the network relative to other packets, and to the maximum throughput per time unit that a station or port assigned to a specific role is permitted. For more information on configuring roles, see Configuring Default VLAN and Class of Service for a Role.

The CoS defines actions to be taken when rate limits are exceeded.

All incoming packets may follow these steps to determine a CoS:

• Classification - identifies the first matching rule that defines a CoS.
• Marking - modifies the L2 802.1p and/or L3 ToS based on CoS definition.
• Rate limiting (drop) is set.
• Transmit queue assignment

The system limit for the number of CoS profiles on a controller is identical to the number of roles. For example, a C5110 can have 1024 roles and 1024 CoS profiles.