Packet switch
Encyclopedia
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 network
s.
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 minicomputer
s. 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 provider
s. However, software is available which allows a personal computer
to function as a low-performance packet switch.
(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.
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.
Node (networking)
In communication networks, a node is a connection point, either a redistribution point or a communication endpoint . The definition of a node depends on the network and protocol layer referred to...
in a network
Telecommunications network
A telecommunications network is a collection of terminals, links and nodes which connect together to enable telecommunication between users of the terminals. Networks may use circuit switching or message switching. Each terminal in the network must have a unique address so messages or connections...
which uses the packet switching
Packet switching
Packet switching is a digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packets. Packet switching features delivery of variable-bit-rate data streams over a shared network...
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
Data link layer
The data link layer is layer 2 of the seven-layer OSI model of computer networking. It corresponds to, or is part of the link layer of the TCP/IP reference model....
. 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 network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
s.
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 minicomputer
Minicomputer
A minicomputer is a class of multi-user computers that lies in the middle range of the computing spectrum, in between the largest multi-user systems and the smallest single-user systems...
s. 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 provider
Internet service provider
An Internet service provider is a company that provides access to the Internet. Access ISPs directly connect customers to the Internet using copper wires, wireless or fiber-optic connections. Hosting ISPs lease server space for smaller businesses and host other people servers...
s. However, software is available which allows a personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...
to function as a low-performance packet switch.
History
The first operational packet switch was the Interface Message ProcessorInterface Message Processor
The Interface Message Processor was the packet-switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989. It was the first generation of gateways, which are known today as routers. An IMP was a ruggedized Honeywell DDP-516 minicomputer with...
(IMP); IMPs were the devices that made up the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
, the first packet switching network. The IMP was developed at Bolt, Beranek and Newman
BBN Technologies
BBN Technologies is a high-technology company which provides research and development services. BBN is based next to Fresh Pond in Cambridge, Massachusetts, USA...
(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.
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
X.25
X.25 is an ITU-T standard protocol suite for packet switched wide area network communication. An X.25 WAN consists of packet-switching exchange nodes as the networking hardware, and leased lines, Plain old telephone service connections or ISDN connections as physical links...
, which were operational around 1972 in a Spanish banking network and then Telenet
Telenet
Telenet was a commercial packet switched network which went into service in 1974. It was the first packet-switched network service that was available to the general public. Various commercial and government interests paid monthly fees for dedicated lines connecting their computers and local...
. They share some commonality with the Forwarding Plane
Forwarding plane
In routing, the forwarding plane, sometimes called the data plane, defines the part of the router architecture that decides what to do with packets arriving on an inbound interface...
of routers, although they differ significantly in the Control Plane
Control plane
In routing, the control plane is the part of the router architecture that is concerned with drawing the network map, or the information in a routing table that defines what to do with incoming packets. Control plane functions, such as participating in routing protocols, run in the architectural...
. Telenet's first packet switches were implemented on Prime commercial minicomputers, followed by a purpose-built switch using multiple 6502 processors.