Cisco Systems CL-28826-01 Defining QoS Class Policing Parameters

63-17

User Guide for Cisco Security Manager 4.4

OL-28826-01

Chapter6 3 Configuring Quality of Service

Quality of Service on Cisco IOS Routers

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Fair queue—Enter the number of queues to reserve for the default class. Values range in powers

of 2 from 16 to 4096. By default, the number of queues is based on the available bandwidth of

the selected interface. For more information, seeTable63-2 on page 63-6.

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Bandwidth—Enter the amount of bandwidth to allocate to this class. You can define this amount

by percentage or by an absolute value of kilobits per second.

Step 4 (Optional) Define one of the following queue length management options:

•Queue Limit—(Default) Specify the maximum number of packets allowed. If you select this option,

tail drop drops excess packets when the queue reaches its capacity.

•WRED Weight for Mean Queue Depth—WRED proactively drops packets until the transmitting

protocol (usually TCP) responds by dropping its transmission rate, thereby alleviating congestion.

Configure WRED by entering an exponential weight factor that is used to calculate the average

queue size.

For more information, see Tail Drop vs. WRED, page63-4.

Note You should change the default only if you are certain that your applications will benefit from a

different value.

Note Do not use WRED with protocols that are not sufficiently robust to reduce their transmission

rates in response to packet loss, such as IPX or AppleTalk. WRED cannot be configured when

you select the Priority percent option.

Step 5 Go to another tab or click OK to save your definitions locally on the client and close the dialog box. The

defined class is displayed in the QoS Classes table on the Quality of Service page.

Step 6 Continue as described in Defining QoS Policies, page 63-10.

Defining QoS Class Policing Parameters

When you define policing parameters, you must specify the average data rate, which determines the

amount of traffic that can be transmitted. In addition, you must specify the action to take on traffic bursts

that exceed this data rate.

You can configure policing for all QoS classes, including the default class. For more information about

policing, see Understanding Policing and Shaping Parameters, page 63-6.

You can also configure policing on the control plane. For more information, see Understanding Control

Plane Policing, page 63-9.