Nokia IPSO 4.0 Configuring Queue Classes, Nokia Network Voyager for Ipso 4.0 Reference Guide 457

Note

A rule treats traffic as if it were configured for "skip," if the traffic matches a rule whose action has been set to "prioritize" or "shape" and no Aggregation Class is configured.

6.Click Apply.

7.Click Save to make your changes permanent.

Configuring Queue Classes

Queue classes are used to instantiate a framework, or template, for output queue schedulers. Like Access Control Lists (ACLs) they are created and configured and then associated with an interface.

There are a maximum of 8 priority-level queues for a queue class. You can configure the size (in packets) of each queue level as well as the queue specifier. The queue specifier is a tag assigned by the classifier and is used as a key to look up the proper queue level. Three queue levels are pre-defined: the Internetwork Control (IC), Expedited Forwarding (EF), and Best Effort (BE) queues. You can assign the remaining queues any name and QueueSpec you want. The table below shows the values that correspond to these queue values:

Name of Queue Level	Priority	IETF DiffServ Codepoint	Queue Specifier Value
Internetwork Control	0	0xc0	7
Expedited Forwarding	1	0xb8	6
Best Effort	7	0	0

When you configure an ACL rule to use the priority action, you must configure an aggregation class. This aggregation class functions as a policer, that is, non-conforming traffic will be dropped. You should configure the aggregation classes so that the aggregate of the NC and EF flows consumes no more than 50% of the output link bandwidth. This action prevents lower- priority traffic from being starved. See RFC 2598 for more information. The other policers should also be configured to prevent the lower-priority queue from being starved.

Internetwork control traffic, such as routing messages and keepalives, should be configured to use the internetwork control queue so that it receives precedence over regular IP traffic. Note that locally originated internetwork control traffic is automatically sent through this queue. See RFC 791 for more information about Internetwork Control traffic.

A queue class can be configured to maximize device throughput or to minimize prioritized traffic latency. The QoS functionality is not achieved without a cost. The choice of QoS with minimal latency is the most costly in terms of forwarding performance, but it allows the least amount of head-of-line blocking for high priority traffic.

Nokia Network Voyager for IPSO 4.0 Reference Guide 457