24 Chapter 1 An Introduction to Policy-Enabled NetworksLayer 2 classifier elementsThe Nortel Ethernet Routing Switch 4500 Series classifies packets basedon the following parameters in the Layer 2 header:• source MAC address/mask• destination MAC address/mask• VLAN ID number (range of)• VLAN tag• EtherType• IEEE 802.1p user priority valuesATTENTIONLayer 2 classifier elements with an Ethernet Type of 0x0800 are treated as anIPv4 classifier, and those with an Ethernet Type of 0x86DD are treated as anIPv6 classifier.System classifier elementsSystem classifier elements support pattern matching, also referred to asoffset filtering. Offset filtering identifies fields within protocol headers, orportions thereof, on which to identify traffic for additional QoS processing.This eliminates the limitations that arise by supporting only certain protocolheader fields, such as IP source address, IP protocol field, and VLAN IDfor flow classification.Fully customized classifiers can be created to match non-IP-based traffic,as well as to identify IP-based traffic using non-typical fields in Layers 2, 3,4, and beyond.The Nortel Ethernet Routing Switch 4500 Series Content Aware Processor(CAE) lookup engine supports selection of 16 bytes within the first 128bytes of the packet.Classifiers and classifier blocksClassifier elements can be combined into classifiers, and grouped intoclassifier blocks. Classifiers are created by referencing an L2 classifierelement, IP element, a system classifier element, or one of each type.Each classifier can have a maximum of a single IP classifier element, oneL2 classifier element, one system classifier element or any combination ofone IP, L2 and system classifier element.Classifiers can be combined into classifier blocks. Each classifier blockhas one or more classifiers.Nortel Ethernet Routing Switch 4500 SeriesConfiguration — Quality of ServiceNN47205-504 (322816-B) 03.01 Standard5.1 23 November 2007Copyright © 2007, Nortel Networks.
