To make a baseband network practical for many computers to
share, the data transmitted by each system is broken up into
separate units called packets. When your computer transmits data
it might be broken up into many packets, and the computer
transmits each packet separately. When all of the packets
constituting a particular transmission reach their destination,
the receiving computer reassembles them back into original data.
This is the basis for a packet-switching network. Circuit-
switching means that the two systems wanting to communicate
establish a circuit before they transmit any information. That
circuit remains open throughout the life of the exchange, and is
only broken when the two systems are finished communicating.
Circuit switching is more common in environments like the public
switched telephone network (PSTN), in which the connection
between your telephone and that of the person you're calling
remains open for the entire duration of the call. In half-duplex
communication data travels in only on