s i d e b a r

PACKET DATA AND NETWORKS

Imagine putting individual magazine pages in envelopes, addressing and mailing them to the same reader. They may or may not take the same route to get there. They may or may not arrive all at once. But when the post office finally delivers them all, the reader can reassemble them into the original magazine.
     That’s the way the Internet works only much, much faster. On a smaller scale, so does CDPD. A document or image is divided into individual packets of digital information, the first digits of which represent an address on the network. These packets are sent across the network, each finding its own way to the final destination where they are electronically reassembled. It can take seconds or it can happen almost instantaneously. This is called a packet-switched network.
     That differs from what is called a circuit-switched network. Traditional telephone systems and some data networks employ this technology, in which a path or circuit is established between two points on the network. The circuit-switched advantage is that communications are often two-way and virtually instant, ideal for voice conversations, for example.
     The disadvantage is that no one else has access to those communications resources while that circuit remains connected. On a packet-switched network, however, data packets to and from different users move together along data highways, separating at network intersections onto other data streams, each sharing the road on the way to its individual goal.
     Many more users can use the system, just as many people can be using the U.S. Postal Service at any one time.

Return to Main Story