Dell PowerConnect J-8216 Software Guide for JUNOS version 10.3 - Page 2934

Dell PowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS Understanding Junos OS CoS Components for J-EX Series Switches This topic describes the Junos OS class-of-service (CoS) components for J-EX Series Switches: • Code-Point Aliases on page 2862 • Policers on page 2862 • Classifiers on page 2862 • Forwarding Classes on page 2863 • Tail Drop Profiles on page 2863 • Schedulers on page 2863 • Rewrite Rules on page 2863 Code-Point Aliases A code-point alias assigns a name to a pattern of code-point bits. You can use this name instead of the bit pattern when you configure other CoS components such as classifiers, drop-profile maps, and rewrite rules. Policers Policers limit traffic of a certain class to a specified bandwidth and burst size. Packets exceeding the policer limits can be discarded. You define policers with filters that can be associated with input interfaces. For more information about policers, see "Understanding the Use of Policers in Firewall Filters" on page 2752. Classifiers NOTE: You can configure policers to discard packets that exceed the rate limits. If you want to configure CoS parameters such as loss-priority and forwarding-class, you must use firewall filters. Packet classification associates incoming packets with a particular CoS servicing level. In the Junos OS, classifiers associate packets with a forwarding class and loss priority and assign packets to output queues based on the associated forwarding class. Junos OS supports two general types of classifiers: • Behavior aggregate or CoS value traffic classifiers-Examines the CoS value in the packet header. The value in this single field determines the CoS settings applied to the packet. BA classifiers allow you to set the forwarding class and loss priority of a packet based on the Differentiated Services code point (DSCP) value, IP precedence value, and IEEE 802.1p value. • Multifield traffic classifiers-Examines multiple fields in the packet such as source and destination addresses and source and destination port numbers of the packet. With 2862