Queue Scaling Limits - Cisco 10000 Series Configuration Manual

Quality of service configuration guide

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Managing Packet Queue Congestion

A Layer 3 queuing strategy provides differentiated levels of service and assigns priority to

delay-sensitive packets. Queuing limits the amount of traffic that can be sent to queues so that all of the

packet buffers are not consumed. Commonly used mechanisms, such as random early detection (RED),

monitor network traffic loads to control congestion by acting on the traffic if congestion is about to

This chapter discusses congestion control mechanisms supported on the Cisco 10000 series router and

includes the following topics:

Queue Scaling Limits

The router allocates at least two queues for every interface or subinterface for which separate queues are

created. The first queue is the default queue for normal traffic and the second queue is the system queue.

The system queue is used for a small amount of router-generated traffic that bypasses the normal drop

mechanisms. For 32,000 VCs, the router would need to allocate a minimum of 64,000 queues. While

Cisco IOS Release 12.3(7)XI1 adds support for up to 128,000 queues, a more effective use of these

limited resources is to have the subinterfaces on a given main interface share the single system queue of

the main interface.

Queue Scaling Limits, page 11-1

Queue Limit, page 11-2

Queue IDs and Interface Queues, page 11-6

Queuing Outbound Traffic, page 11-7

Controlling Congestion Using Tail Drop, page 11-8

Controlling Congestion Using Random Early Detection, page 11-9

Controlling Congestion Using Weighted Random Early Detection, page 11-11

Interfaces Supporting Layer 3 Packet Drop Policies, page 11-21

Restrictions and Limitations for Controlling Layer 3 Congestion, page 11-22

Configuring Layer 3 Queue Limit and Drop Policies, page 11-24

Verifying and Monitoring Layer 3 Packet Dropping, page 11-32

Controlling Packet Flow on Layer 2 Queues, page 11-39

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