Abstract

  

   In the minds of most people, data communication is a recent phenomenon associated with computer communications, but data messaging predated the telephone by several decades. Samuel F.B. Morse invented the first data communication device. Protocols are specialized computer programs that either exist in software or in firmware chips. Most desktop computers contain both varieties. The Ethernet LAN protocol, which comes with all new computers, is encoded into firmware.LANs operate at the first two layers of the OSI model: physical and datalink. The protocol metaphor is apt for data because devices must behave according to defined procedures. Contrasted to voice sessions, which typically average 3 or 4 min, data sessions extend from log-on to log-off, which may be days or months apart. The TCP/IP protocol operates in this way. IP is a connectionless protocol that allows packets to traverse the packet as individual PDUs known as datagrams. Data and voice both ride over the same physical fiber-optic backbone, but at the circuit level they are mostly separate. That, however, is changing. A frame relay network is provisioned within common carrier facilities, and is fully as secure as a network composed of dedicated point-to-point lines. It is economical, and offers bandwidth on demand up to the capacity of the input port.The user is concerned only with obtaining the access channel in an IP network.Once the channel is up, the endpoint can connect anywhere in the world without carrier intervention.