ion. These frames are then passed through a serialization and deserialization (serdes) module before they are handed over to the transceiver. The inverse occurs at the reception point. Network processors can obviously han- dle the framing function in the high-speed links of the future. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. PACKET PROCESSING 52 NETWORK PROCESSORS Pattern Search and Packet Classification The generic classification task (as the term itself implies) means that some rules and conditions must be applied in real time to every incoming packet and, more specifically, to its headers or to parts of its overall content in order for the switch/router to assign the packet to one among several logical come options. This is usually associated with specific QoS or forwarding decisions. Typically, a table of addresses and, more recently, the whole database of rules and policies must be searched in real time SO a context-sensitive decision can be made, according to which packet will be classified and for- warded. As a result of classification, the incoming stream of packets gets partitioned into multiple logically separated output streams, which will then need to be handled appropriately. For instance, one stream of packets may need to be forwarded to its destination port with a higher priority, whereas another stream may have to be relegated to a lower priority because of other more urgent tasks. One of these output streams might also be the subject of a special billing procedure, whereas another may not. Traditionally, especially in older routers where the line speed was quite low compared to the more recent generations of very fast switching/routing gear where the high wire speed requires hardware implementations of the classification work, packet classification algorithms were implemented in soft- ware that was running on a stand