Cisco PIX 525 Specifikace stáhnout pdf (Strana 324)

100

101

20-10

Cisco Security Appliance Command Line Configuration Guide

OL-6721-01

Chapter 20 Applying QoS Policies

Applying Low Latency Queueing

Note The upper limit of the range of values for the queue-limit and tx-ring-limit commands is determined

dynamically at run time. To view this limit, enter help or ? on the command line. The key determinants

are the memory needed to support the queues and the memory available on the device. The range of

queue-limit values is 0 through 2048 packets. The range of tx-ring-limit values is 3 through 128 packets.

Configuring Priority Queuing

You must use the priority-queue command, in global configuration mode, to create the priority queue

for an interface before priority queuing takes effect. You can apply one priority-queue command to any

interface that can be defined by the nameif command. All other traffic is delivered on a best-effort basis.

In general, you can apply a priority-queue command to any interface that can be defined by the nameif

command. The priority-queue command enters priority-queue mode, as shown by the prompt, which

lets you configure the maximum number of packets allowed in the transmit queue and the size of the

priority queue.

Note You cannot enable both priority queuing and policing together. In other words, only packets with normal

priority can be policed; packets with high priority are not policed.

Sizing the Priority Queue

The size that you specify for the priority queue affects both the low latency queue and the best-effort

queue. The queue-limit command specifies a maximum number of packets that can be queued to a

priority queue before it drops data. This limit must be in the range of 0 through 2048 packets.

Reducing Queue Latency

The tx-ring-limit command lets you configure the maximum number of packets (that is, the depth)

allowed to be queued in the Ethernet transmit driver ring at any given time. This allows for fine-tuning

the transmit queue to reduce latency and offer better performance through the transmit driver. This limit

must be in the range 3 through 128 packets on the PIX platform.

The default queue-limit is the number of average, 256-byte packets that the specified interface can

transmit in a 500-ms interval, with an upper limit of 2048 packets. A packet that stays more than 500 ms

in a network node might trigger a timeout in the end-to-end application. Such a packet can be discarded

in each network node.

The default tx-ring-limit is the number of maximum 1550-byte packets that the specified interface can

transmit in a 10-ms interval. This guarantees that the hardware-based transmit ring imposes no more than

10-ms of extra latency for a high-priority packet.

1 2 ... 319 320 321 322 323 324 325 326 327 328 329 ... 603 604

Komentáře k této Příručce

Žádné komentáře

Cisco PIX 525 Specifikace Strana 324

Komentáře k této Příručce