|
A packet switch is a node in a network which uses the packet switching paradigm for data communication. Packet switches can operate at a number of different levels in a protocol suite; although the exact technical details differ, fundamentally they all perform the same function: they store and forward packets. One common class of contemporary packet switches are the bridge and network hub, which interconnect multiple network segments at the data link layer. Another is the router, a device which operates at the internetwork layer, and connects dissimilar kinds of networks, such as serial lines and local area networks. Generally, packet switches only perform communication-related functions, but in some systems the computers which performed the packet-switching function were also used for data storage and computation. Originally, packet switches were built around standard minicomputers. Today, almost all packet switches are specialized hardware devices, ranging in size and performance from small local hubs up to the large switching systems used by major Internet service providers. However, software is available which allows a personal computer to function as a low-performance packet switch. ==History== The first operational packet switch was the Interface Message Processor (IMP); IMPs were the devices that made up the ARPANET, the first packet switching network. The IMP was developed at Bolt, Beranek and Newman (BBN) as part of their contract to build out the original ARPANET, and the first functional IMP was placed at UCLA on August 30, 1969. 〔(IMP -- Interface Message Processor ), LivingInternet Accessed June 22, 2007.〕 〔(Looking back at the ARPANET effort, 34 years later ), Dave Walden, Accessed June 22, 2007.〕 〔(A Technical History of the ARPANET - A Technical Tour ), THINK Protocols team, Accessed June 22, 2007.〕 The IMP and the packet switches that followed it are what make the Internet possible. The next generation of early packet switches were those for X.25, which were operational around 1972 in a Spanish banking network and then Telenet. They share some commonality with the Forwarding Plane of routers, although they differ significantly in the Control Plane. Telenet's first packet switches were implemented on Prime commercial minicomputers, followed by a purpose-built switch using multiple 6502 processors. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Packet switch」の詳細全文を読む スポンサード リンク
|