26-19
Ethernet Card Software Feature and Configuration Guide, R7.2
January 2009
Chapter 26 Configuring IEEE 802.17b Resilient Packet Ring
Configuring Fairness Weights
Configuring Fairness Weights
RPR-IEEE has a configurable fairness system, used to control congestion on each ringlet. This feature
moderates bandwidth utilization of the ringlet to minimize and potentially eliminate starvation of any
station. Each station has two instances of the fairness machine, to control traffic that is being transmitted
and transited out of each span of the interface. Each fairness machine is devoted to a particular ringlet,
and controls the traffic that is destined to that ringlet.
Each ringlet in an unwrapped ring is independent, an d the fairness configuration can differ for each
direction. The default is to configure both directions, but you can optionall y specify east or west in the
configuration.
The local station weight impacts how congested the station appears relative to other stations in the
ringlet. It also affects how much more bandwidth a station can use. A higher weight gives the local
station a greater share of the ringlet bandwidth. A lower weight decreases the bandwidth share of the
local station. The default value is 0 configured as an exponent of 2, which yields an effective weight of 1.
To enable and configure the fairness weight, perform the following procedure, beginning in global
configuration mode:
Configuring RPR-IEEE Service Classes Using the Modular QoS CLI
Traffic is directed to the three service classes supported by RPR-IEEE by using the standard Cisco
Modular QoS CLI (MQC). MQC is a CLI structure that allows you to create traffic policies and attach
these policies to interfaces. A traffic policy contains a traffic class and one or more QoS features. A
traffic class classifies traffic, while the QoS features in the traffic policy determine how to treat the
classified traffic.
For more information on general MQC configuration, refer to the following Cisco IOS documents:
Step 4 Router(config)# end Returns to privileged EXEC mode.
Step 5 Router# copy running-config startup-config (Optional) Saves configuration changes to the
TCC2/TCC2P flash database.
Command Purpose
Command Purpose
Step 1 Router(config)# interface rpr-ieee 0 Activates interface configuration mode to
configure the RPR-IEEE interface.
Step 2 Router(config-if)# rpr-ieee fairness weight
weight [east | west]
Specifies the weight for a station on the ringlet.
Values can range from 0 to 7 and are configured as
an exponent of 2, which results in weights ranging
from 1 to 128. The default value is zero.
(Optional
Step 3 Router(config)# no shut Enables the RPR-IEEE interface and changes the
mode from the default passthrough.
Step 4 Router(config)# end Returns to privileged EXEC mode.
Step 5 Router# copy running-config startup-config (Optional) Saves configuration changes to the
TCC2/TCC2P flash database.