User Guide
31-3
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
78-14099-04
Chapter 31 Configuring PFC QoS
Understanding How PFC QoS Works
• The PFC does not provide QoS for FlexWAN module ports. Refer to the following publications for
information about FlexWAN module QoS features:
–
Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.1:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_c/index.htm
–
Cisco IOS Quality of Service Solutions Command Reference, Release 12.1:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_r/index.htm
–
Class-Based Marking:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/cbpmark2.
htm
–
Traffic Policing:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/dtpoli.htm
–
Distributed Class-Based Weighted Fair Queueing and Distributed Weighted Random Early
Detection:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/dtcbwred.
htm
–
Distributed Low Latency Queueing:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/dtllqv
ip.htm
–
Configuring Burst Size in Low Latency Queueing:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t3/dtcfg
bst.htm
–
Distributed Traffic Shaping:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121t/121t5/dtdts.htm
–
MPLS QoS:
http://www.cisco.com/univercd/cc/td/doc/product/core/cis7600/cfgnotes/osm_inst/mpls.htm
QoS Terminology
This section defines some QoS terminology:
• Packets carry traffic at Layer 3.
• Frames carry traffic at Layer 2. Layer 2 frames carry Layer 3 packets.
• Labels are prioritization values carried in Layer 3 packets and Layer 2 frames:
–
Layer 2 class of service (CoS) values, which range between zero for low priority and seven for
high priority:
Layer 2 Inter-Switch Link (ISL) frame headers have a 1-byte User field that carries an IEEE
802.1p CoS value in the three least significant bits.
Layer 2 802.1Q frame headers have a 2-byte Tag Control Information field that carries the CoS
value in the three most significant bits, which are called the User Priority bits.
Other frame types cannot carry Layer 2 CoS values.