How to Define Priority-Based Rate Limits

Priority-based rate limits are supported in Policy Manager for use with legacy devices such as the E7 and E1 devices. For information on defining role-based rate limits for N-Series, S-Series and K-Series devices, see How to Define Rate Limits.

Priority-based rate limits are associated with one or more of the eight 802.1p priorities (0-7). When the associated priority is selected for a class of service, the rate limit becomes part of that class of service.

When priority-based rate limiting is implemented, the combined rate of all traffic on the port that matches the priorities associated with the rate limit cannot exceed the configured limit. If the rate exceeds the configured limit, frames are dropped until the rate falls below the limit.

In order to control traffic inbound and outbound on the same port, two rate limits must be configured (one inbound and one outbound).

Instructions on:

Defining Priority-Based Rate Limits

To define a priority-based rate limit:

  1. Open the Class of Service Configuration window (available from the Policy Manager Edit menu).
  2. Select the Show all CoS Components in Tree (Advanced Mode) option from the Domain Managed CoS Components menu to display the CoS tree in the left panel.
  3. In the left-panel tree, expand the CoS Components folder.
  4. Right-click the Rate Limits folder and select Create Rate Limit.
  5. In the Create Rate Limit window, specify the desired rate limit and click OK. The rate limit will be created under the left-panel Rate Limits folder. Note that rate limit actions are not supported by priority-based rate limits and are ignored.
  6. Select the rate limit and display the General tab in the right panel.
  7. In the Description field, click the Edit button and enter a description for the rate limit.
  8. In the Priority-Based Configuration sub-tab:
    1. Select Inbound or Outbound direction, depending on whether the rate limit is for inbound or outbound traffic.
    2. Select the 802.1p priority or priorities with which the rate limit will be associated. Each 802.1p priority can have only one inbound and one outbound rate limit; therefore, if a priority is already being utilized for the selected direction, it is grayed out.
    3. If you are creating a rate limit to be used on C2/B2 10/100 ports, select either Low to associate the rate limit with priorities 0-3 or High to associate the rate limit with priorities 4-7. You can select both Low and High if you want to associate the rate limit with priorities 0-7. If the Low or High priority is already being utilized for another rate limit, it will be grayed out. Because C2/B2 10/100 ports only support inbound rate limits, this section will be grayed out if you have selected Outbound for your rate limit Direction.
    4. Click the Precedence Edit button. This opens the Precedence tab, where you can change the order in which priority-based rate limits will be written to devices that support them. This is useful on legacy devices which support a varying number of rate limits.
    5. If you want to specify any network elements to which this rate limit will not apply, go to the Exclusion area, click Edit, and make your selection from the list of network elements. Click OK.
  9. Verify that priority-based rate limiting is enabled in the Class of Service Mode section on the device General tab or via the Device Configuration Wizard.
  10. Enforce.

Priority-based rate limits add to the amount of time it takes to enforce and verify roles. Once you've created your rate limits and enforced them, you may want to disable rate limits so that it takes less time to enforce. You can disable rate limits in the Class of Service Mode section of the device General tab.

Once a rate limit is associated with a priority, that priority will include rate limiting wherever and however it is used, until the rate limit is deleted from Policy Manager. Also, once a priority-based rate limit is applied to a port, it will remain on the port even if the role that originally used the rate limit is no longer associated with the port.

Removing a Priority-Based Rate Limit

Once a priority-based rate limit is associated with a priority, that priority will include rate limiting wherever and however it is used, until the rate limit is deleted from Policy Manager. In addition, once the rate limit is applied to a port, it remains on the port even if the role that originally used the rate limit is no longer associated with the port.

To remove a priority-based rate limit, you must delete it from Policy Manager and then perform an Enforce with priority-based rate limiting enabled. This will remove the rate limit from any ports it was applied to.

  1. Open the Class of Service Configuration window (available from the Policy Manager Edit menu).
  2. Select the Show all CoS Components in Tree (Advanced Mode) option from the Domain Managed CoS Components menu to display the CoS tree in the left panel.
  3. Expand the CoS Components folder and the Rate Limits folder.
  4. Right-click the rate limit you want to remove, and select Delete from the menu.
  5. Verify that priority-based rate limiting is enabled in the Class of Service Mode section on the device General tab or via the Device Configuration Wizard.
  6. Enforce.

Related Information

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