Configuring QoS Traffic Policing and Shaping
OmniSwitch AOS Release 7 Network Configuration Guide June 2013 page 25-25
greater than the value of the specified CIR. In this case, the trTCM mode is triggered; otherwise, the
srTCM mode is used.
• This implementation of TCM is in addition to the basic rate limiting capabilities provided through the
maximum bandwidth and maximum depth parameters used in QoS policy actions and the ingress and
egress bandwidth parameters used in VLAN Stacking Service Access Point (SAP) profiles. When these
parameters are used, the TCM meter operates in the Single-Rate TCM mode by default.
• A srTCM policy action specifies both a CBS and PBS value. Default values for these burst sizes are
used if one is not specified using the optional cbs and pbs parameters.
• Configure the PBS and CBS with a value that is greater than or equal to the size of the largest IP
packet in the metered stream.
To configure a TCM QoS policy action, use the policy action cir command with one or more of the above
parameters. Configuring the cbs and pbs parameters is optional. If a value is not specified for either one,
the default value is used for both parameters. For example:
-> policy action A1 cir 10M
To specify one or both of the burst size values, use the cbs and pbs parameters. For example:
-> policy action A2 cir 10m cbs 4k
-> policy action A3 cir 10m cbs 4k pbs 10m
All of these command examples configure the TCM meter to operate in the Single-Rate TCM (srTCM)
mode. To configure the meter to operate in the Two-Rate TCM (trTCM) mode, use the pir parameter and
specify a peak information rate value that is greater than the committed information rate value. For exam-
ple, the following commands configure the meter to use the trTCM mode:
-> policy action A4 cir 10m cbs 4k pir 20m
-> policy action A5 cir 10m cbs 4k pir 20m pbs 40m
Once a TCM policy action is configured, the action can be used in a policy rule to rate limit traffic accord-
ing to the specified rates and burst sizes. Traffic that matches a TCM policy is marked green, red, or
yellow based on the rate limiting results.
To remove the TCM configuration from a QoS policy action, use the no form of the policy action cir
command. For example:
-> policy action A6 no cir
TCM Policy Example
Once configured, a TCM policy action is then available to use in a QoS policy rule to apply color mark-
ing to a specified traffic stream.
First, create a condition for the traffic. In this example, the condition is called ip_traffic. A policy action
(tcm1) is then created to enforce ingress rate limiting using TCM.
-> policy condition ip_traffic source ip 10.10.5.3
-> policy action tcm1 cir 5m cbs 4k pir 10m pbs 20m counter-color green-nongreen
-> policy rule rule1 condition ip_traffic action tcm1
Note that the rates and burst sizes can be specified in abbreviated units, in this case, 10m.
The rule is not active on the switch until the qos apply command is entered. When the rule is activated,
any flows coming into the switch from source IP address 10.10.5.3 is metered and marked according to the
TCM policier parameters specified in the tcm1 policy action.
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