 this dis- cussion and appreciate the following challenges: The nature of the operations involved with fast packet processing. The way routers/switches are currently built. The types of physical modules one typically expects to find inside a router/switch chassis. How it all fits together with the latest trends in component integration-namely, chipsets of NPUs, search engines, classification and forwarding processors, switch fabrics, traffic managers, and secu- rity coprocessors. These trends address these combined requirements in the new design era, which we described in Chapter 2, "Network Processors: Justification." NETWORK CONTEXTS: CLIENT, ACCESS, EDGE, AND CORE Before we look more closely at the inner structures of systems and operations, we must clarify some common terms that will be used in this discussion. A reader who has had exposure to carrier-based services and products should be very familiar with this nomenclature. However, experience shows that many technical and business managers in the telecommunications industry either ignore many of the subtle, but nevertheless important, distinctions between these terms, or even worse hear them and use them without knowing exactly what they mean. The nuances become more important when the equip- ment requirements for the various realms are examined. A router designed for an enterprise network or a college campus where only moderate quantities of Internet Protocol (IP) traffic must be handled is quite different from a multiservice router (MSR) that is capable of multiple layer 2 and 3 protocols operating in the long-distance core of a wide area network (WAN) backbone between Internet serv- ice providers (ISPs) and legacy voice-based traffic carriers. However, most people refer to them with the same generic name of router. 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 4