A survey of modern high-performance switching techniques

INTRODUCTION This book is about the performance evaluation of high-speed switching fabrics and networks. More simply, it concerns how the next generation of telecommunications technology can be designed, analyzed, and understood. But this idea requires some explanation. The roots of today's high-speed switching technology go back to the advent of the digital computer in the 1940s. For the first time, machines were built containing information with a binary, or digital, representation. It was only a matter of time before interest grew in transporting this digital information from place to place. At first the digital information was simply transformed into analog form for transport over analog telephone circuits. During the 1960s, though, the concept of a packet-switching network was developed. The idea behind a packet-switching network was to create a network of dedicated leased lines whose sole function would be to transport digital data traffic. At the source, data would be divided into groups of bits called packets. An actual packet has two parts. The first part is the header field, which is a group of bits containing such information as a packet's destination , its origination point, its priority and its error codes. The second part is the actual information field. This part is the group of information bits to be transported over the network. Algorithms running in the switching nodes read a packet's destination address and route the packet over the next successive link on its way to its destination. A great advantage of packet-switching technology was its inherent statistical multiplexing [6]—that is, a leased line is shared by the data traffic between many users. This lowers the cost of transmitting data. Moreover, statistical multiplexing allows the inherently bursty data traffic to be combined into aggregate flows that can be accommodated economically by long-lasting leased-line connections. Packet-switching technology was first used in early networks such as the U.S. ARPANET. Today packet-switching technology is widely implemented in such general user networks as the Internet and in such specialized applications as the control network for telephone networks, Common Channel Signaling System 7. Through the 1980s packet-switching technology was used exclusively for digital data transport. As such it filled an important function in the telecommunications world. To put this in perspective, though, the total bandwidth of all the world's packet-switching networks was still a tiny fraction of the total bandwidth of the world's telephone networks. However, this could change with the introduction …