6.3.2. Packet switching

Instead of keeping a connection open for the entire length of the call, packet networks break the digital stream of ones and zeros into chunks of the same length. These chunks, or ‘packets’, are then put into the computer equivalent of an envelope, with some information such as the origin and destination, or ‘address’, of the packet, and a serial number that indicates the sequence number of the packet or its ‘place in line’. In place of switches, which merely connect and disconnect circuits, packet networks use routers – computers that read the address of a packet and pass it to another router closer to the destination. At the destination, a few thousandths of a second later, the packets are received, reassembled in the correct order and converted back into the original message. Here is an illustration of how it works.

Figure 9: packet switching