Packet switching is a technology that splits data in network communications into manageable small pieces, called packets. By sending a large file in several small chunks over a network, packet switching minimizes the impact of data transmission errors. Traffic bottlenecks are avoided too, allowing data to flow in the most efficient manner possible over the network.
The idea of network communications involves following an exact set of rules to move the data from one location, or node, on the network to another. The Internet is simply a large network, and packet switching occurs when moving all data across the Internet. Transport Control Protocol/Internet Protocol (TCP/IP) and Frame Relay are examples of packet switching protocols. Some mobile phone technologies also use this type of technology.
When employing packet switching, the network routing software divides the file into several small packets of data of between 1,000 and 1,500 bytes each, labeling each packet with header information. In the header, the routing software includes instructions for reassembling the file from the packets in the correct order. It also includes the destination information, before sending the packets over the network.
As the packets travel across the network, they might be separated, taking different routing paths, depending on Internet traffic. The routers and switches on the network use the header information to determine the most efficient route for moving each packet to its destination. Packet switching allows for efficient use of network bandwidth, as sending numerous small packets fits into the network capacity better than sending large files intact. Once the packets arrive at the destination, regardless of the order in which they arrive, the routing software reassembles the file correctly, using the header information. If all of the packets arrived intact and free of errors, the file is ready for use. However, if a packet arrived with an error, the routing software can request that the packet be resent. By using this technology, only a portion of the entire file has to be resent, which lessens overall network traffic.
Paul Baran and Donald Davies each developed the idea of packet switching independently in the early 1960s. It is an improvement on circuit switching technology, commonly used in landline telephone networks for many years. With circuit switching, a dedicated line carries all of the data traffic related to a particular file. Circuit switching works well for delivering a large file quickly because it has no delays. However, moving a large amount of data to and from thousands of nodes simultaneously, such as occurs on the Internet, would be impossibly inefficient using circuit switching.