ser and the developer communities. We will elaborate on their privileged cost/perform- ance/flexibility positioning with respect to alternative design approaches-for example, architectures that rely heavily on the more traditional use of application-specific integrated circuits (ASICs) or reduced instruction set computer/complex instruction set computer (RISC/CISC) computing plat- forms to accomplish the same functions. By understanding the context in which network processors are revolutionizing the networking and communications industries, the reader will be properly equipped to tackle the fundamental technologies and internal technical intricacies that make up the heart and brain of the network processor microchips and the systems they enable. WHAT ARE NETWORK PROCESSORS? Network processors, also known in the industry and product literature of several vendors as network processor units (NPUs), are highly programmable specialized integrated circuits (processors). These circuits are used in the high-speed communications industry. They are used to optimize the perform- ance of packet processing in the evolving functional framework of broadband network equipment. Because of the unmistakable convergence of networks that we briefly discussed in the previous chapter, packet processing becomes the overriding function that is expected to be properly imple- mented in high-speed networking equipment such as routers, switches, and SO on. Obtaining the appropriate performance and functionality in network devices is one of the key factors for determin- ing the usefulness, desirability, and business potential of these devices within the corporate or serv- ice provider markets. Throughout this book, we use the term packet in a general sense to describe a datagram unit, mean- ing either a cell, packet, or frame. If we are discussing something very network specific, such as the Asynchronous Transfer Mode (ATM) environment, we will call the datagram unit a cell. Downloaded from Digital Engineering Library @ McGraw-Hill (www.digit