Specifications

White Paper
© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information. Page 31 of 89
7. Configuring (Port ASIC based) QoS on the Catalyst 6500
QoS configuration instructs either the port ASIC or the PFC to perform a QoS action. The following sections will look
at QoS configuration for both these processes. On the port ASIC, QoS configuration affects both inbound and
outbound traffic flows.
Figure 24. Ingress QoS Processing Flow
From the above diagram it can be seen that the following QoS configuration processes apply
1. Trust states of ports
2. Applying port based CoS
3. Determine CoS Mutation
4. Receive Drop Threshold assignment
5. CoS to Receive Drop threshold maps
Figure 25. Egress QoS Processing Flow
When a frame is processed by either the MSFC or the PFC, it is passed to the outbound port ASIC for further
processing. Any frames processed by the MSFC will have their CoS values remapped using the ip precedence value
of the packet. This needs to be taken into consideration for QoS processing on outbound ports.