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Packet switching

From Academic Kids

In computer networking and telecommunications, packet switching is the now-dominant communications paradigm, in which packets (messages or fragments of messages) are individually routed between nodes, with no previously established communication path. Packet switching is used to optimize the use of the bandwidth available in a network, and to minimise the transmission latency (i.e. the time it takes for data to pass across the network).

A packet is a block of user data together with necessary address and administration information attached, to allow the network to deliver the data to the destination. Analogous to a physical packet sent through the mail, with the address written on the outside, this provides the information which the network (the postal service) needs to get the packet to the correct destination.

Packets are routed to their destination through the most expedient route (as determined by some routing algorithm). Not all packets travelling between the same two hosts, even those from a single message, will necessarily follow the same route.

One data connection will usually carry a stream of packets of data that will not necessarily be all routed the same way over the physical network. The destination computer reassembles the packets into their appropriate sequence.

Packet switching was invented by Donald Davies and Paul Baran in the early 1960s. Some people claim that Leonard Kleinrock also invented packet switching, but Davies contested this prior to his death and pointed out that Kleinrock's research was actually in queueing theory, which is a key theoretical underpinning to packet switching. Kleinrock's published works nowhere prominently mention breaking a user's message up into segments, and sending the segments through the network separately, which was the key innovation in Baran's and Davies' work.

The most well-known use of the packet switching model is the Internet, which is a packet-switched network, running the Internet Protocol layer 3 protocol over a variety of other network technologies. Ethernet, X.25 and Frame relay are international standard layer 2 packet switching networks. Newer mobile phone technologies such as GPRS and i-mode also employ packet switching.

Packet switching is also called connectionless networking, because it is the opposite of circuit switched or connection-oriented networking, although technologies such as MPLS are beginning to blur the boundaries between the two. ATM is another hybrid technology, which uses cell relay instead of packet switching.

Fast packet switching is a packet switching technique that increases the throughput by eliminating overhead.

Contents

See also

Further reading

  • Katie Hafner, Where Wizards Stay Up Late (Simon and Schuster, 1996)

Reference

  • Paul Baran, On Distributed Communications (http://www.rand.org/publications/RM/baran.list.html)
  • Paul Baran, On Distributed Communications Networks (IEEE Transactions on Communications Systems, March 1964)
  • Leonard Kleinrock, Information Flow in Large Communication Nets (http://www.lk.cs.ucla.edu/LK/Bib/REPORT/PhD/), (MIT, Cambridge, May 31, 1961) Proposal for a Ph.D. Thesis
  • Leonard Kleinrock, Communication Nets: Stochastic Message Flow and Design (McGraw-Hill, 1964)

External links

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.
de:Paketvermittlung

fi:Pakettikytkent it:Commutazione di pacchetto no:Pakkesvitsjing sk:Prepnanie paketov zh:分组交换

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