ABSTRACT
This chapter explores the basic communication technology that the Internet uses. It describes the fundamental mechanism all computer networks use to transfer data, and explains why the scheme works well. To avoid the expense and inconvenience of running a dedicated connection between each pair of communicating devices, a computer network arranges for multiple devices to share the underlying transmission facilities. To avoid situations where the data transfer by one device leaves others waiting, networking researchers invented a system that prevents long delays. The idea is straightforward: instead of allowing a given device to use the network for an arbitrarily long time, limit the amount of data that a device can transfer on each turn. The idea, which was invented in the 1960s, is called packet switching, and the unit of data that can be transferred is called a packet. Both Local Area Networks and Wide Area Networks use packet switching, as do both wired and wireless networks.
