Understanding CoS Classifiers
Packet classification associates incoming packets with a particular class-of-service
(CoS) servicing level. Classifiers associate packets with a forwarding class and loss
priority and assign packets to output queues based on the associated forwarding class.
There are two general types of classifiers:
•
Behavior aggregate (BA) classifiers
•
Multifield (MF) classifiers
You can configure both a BA classifier and an MF classifier on an interface. If you do this,
the BA classification is performed first and then the MF classification. If the two
classification results conflict, the MF classification result overrides the BA classification
result.
NOTE:
When a source media access control (MAC) address is learned, the
frame that contains the source MAC address is always sent out on queue 0
while egressing from the network interface, irrespective of the classifier
applied to the ingress interface.
On Juniper Networks EX8200 Ethernet Switches, you can specify BA classifiers for bridged
multidestination traffic and IP multidestination traffic. The BA classifier for multicast
packets is applied to all interfaces on the EX8200 switch.
This topic describes:
•
Behavior Aggregate Classifiers on page 3153
•
Multifield Classifiers on page 3155
Behavior Aggregate Classifiers
The behavior aggregate classifier maps a CoS value to a forwarding class and loss priority.
The forwarding class determines the output queue. The loss priority is used by a scheduler
to control packet discard during periods of congestion.
There are three types of BA classifiers:
•
Differentiated Services Code Point (DSCP) for IP DiffServ
•
IP precedence bits
•
IEEE 802.1p CoS bits
BA classifiers are based on fixed-length fields, which makes them computationally more
efficient than MF classifiers. Therefore core devices, which handle high traffic volumes,
are normally configured to perform BA classification.
3153
Copyright © 2010, Juniper Networks, Inc.
Chapter 107: Class of Service (CoS)—Overview
Summary of Contents for JUNOS OS 10.3 - SOFTWARE
Page 325: ...CHAPTER 17 Operational Mode Commands for System Setup 229 Copyright 2010 Juniper Networks Inc ...
Page 1323: ...CHAPTER 56 Operational Mode Commands for Interfaces 1227 Copyright 2010 Juniper Networks Inc ...
Page 2841: ...CHAPTER 86 Operational Commands for 802 1X 2745 Copyright 2010 Juniper Networks Inc ...
Page 3367: ...CHAPTER 113 Operational Mode Commands for CoS 3271 Copyright 2010 Juniper Networks Inc ...
Page 3435: ...CHAPTER 120 Operational Mode Commands for PoE 3339 Copyright 2010 Juniper Networks Inc ...
Page 3529: ...CHAPTER 126 Operational Mode Commands for MPLS 3433 Copyright 2010 Juniper Networks Inc ...
