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In this article:
- What is packet switching?
- How routing is decided?
- Networks using packet switching
- History of packet switching
- Applications of packet switching
What is Packet Switching?
Packet switching is a paradigm that helps in communication inside a network or between networks of computers. In packet switching, information is divided into small units called packets and these are individually routed between nodes over data links which might be shared by many other nodes. It is an opposite to circuit switching, where a dedicated connection between two nodes is setup for their exclusive use for the duration of the communication. Packet switching optimizes the bandwidth available in a network and minimizes the time it takes for data to pass across the network and increases the robustness of communication.
In this method, the data is split up into small packets and each is labeled with the complete destination address and then routed individually. Packet switching is ‘connectionless networking’ because no connections are established.
How routing is decided?
Packets are routed to their destination by using a routing algorithm. This algorithm creates paths based on various metrics and desirable qualities of the routing path. Once a route has been decided for a packet, it is it is sent along that path. However, the same route may or may not be used for the following packets.
The Actor model of concurrent computation in which messages sent to the same address may be delivered in an order different from the order in which they were sent is based on this paradigm.
Networks using packet switching
The Internet is the network that makes the use of packet switching. It is the largest network to do so. The internet uses the internet protocol suite over a variety of data link layer protocols.
Modern mobile phone technologies such as GPRS are also packet switching networks.
Fast packet switching is another packet switching technique that increases the throughput by eliminating overhead.
History of packet switching
The concept of packet switching had been given individually by Paul Baran and Donald Davies. An early research done by Leonard Kleinrock and published a book in the related field of digital message switching (without the packets) in 1961, later played a leading role in building and management of the world's first packet switched network, the ARPANet.
Baran made the concept of packet switching during a research for the US Air Force for communications networks. Baran's paper described an architecture for a large-scale, distributed communications network. The paper focused on three thins:
- A decentralized network with multiple paths between any two points;
- Division of complete messages into message blocks (packets)
- Delivery of these messages by store and forward switching.
Baran's study found its use when Lawrence Roberts was given the responsibility of developing the ARPANet by the computer scientist Robert Taylor at Information Processing Technology Office.
Baran's research was similar to the research performed independently by Donald Davies at the National Physical Laboratory, UK. In 1965, Davies developed the concept of packet switched networks and proposed development of a UK wide network.
Davies also had some of the same parameters for his original network design as Baran, an example being the packet size of 1024 bits. The term ‘packet switching’ was taken from Davies’s work.
Davies helped build a packet switched network called the Mark I to serve the NPL in the UK in 1970. The Mark II replaced it in 1973, and remained in operation until 1986, influencing other research in the UK and Europe.
Applications of Packet Switching
There are various protocols today that make use of the packet switching technique. All of them pertain to the Wide Area Network. These are as follows:
- Transmission Control Protocol/Internet Protocol (TCP/IP)
This is the protocol that the Internet uses to transfer information or data from a source to a destination.
- Frame Relay
This is another protocol that uses packet switching. It provides speeds from 1.5 Mbps to 45 Mbps and is a very advanced form of a network.
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