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How Switching Works

It is anticipated that extremely dynamic traffic routing procedures will be employed, implemented by programs in each IMP. In particular a version of the Baran (of RAND) hot potato method may he employed. The notion of the packet (an entity of 1000 bits maximum) was introduced, where a given message could be composed of many packets. The routing mechanism would deal with the packet, thus packets of the same message may traverse different routes from source to destination.

- Elmer Shapiro; Computer Network Meeting of Oct 9-10, 1967; Nov 1967.

Switching systems enable packet networks to dynamically optimize their operation and recover from localized damage. The switching in Internet networks is performed by computers called routers at the intersection where networks come together. Internet routers use a number of standard routing protocols to switch the incoming packets from one network to another as required.

Since routing software can reconfigure instantly, packet switching networks can adapt to downed links and maintain communications by roundabout paths even under very adverse conditions. Since the systems are operating at electronic speed, this means messages can be sent through even large, damaged networks very quickly.

One of the biggest advantages of packet switched networks is that they use the available bandwidth very efficiently by sharing it at all times, so that no one communication ties up a communication link. In the early 1970's, the cost of electronics came down to the point where this model became cost-effective, and it became possible to install routing equipment at each network node, enabling wide area communications for the first time.

Today's Internet routing protocols use sophisticated algorithms that have been optimized for efficiency over many years. In practice, most network connections today are very reliable, and so all packets for a given computer are usually sent over the same path as long as it remains operational.

Today, switches are getting faster and faster, with optical switches providing large advances in speed, and the ultimate end result is now within site: near zero switching time as a packet moves from one network to another at near the speed of light.