3Com 500 manual Appendix C Glossary

C-4 APPENDIX C: GLOSSARY

D Channel A control channel carrying signalling information, running at 16 Kbps. The basic rate ISDN 2 service carries two B channels plus one control D channel. Refer to ISDN and B Channel.

Data Characters or code either entered by the user or passed between devices that are part of the computer or network.

Data communications The transfer of data via transceiver equipment by means of data transmission according to a protocol. Refer to Protocol.

Datagram A message that is sent from one computer or device to another to confirm it location or status on a network.

Data link layer The second layer of the OSI reference model. This layer is responsible for controlling message traffic.

Data packet (packet) A sequence of binary digits, including data and control signals that is transmitted across a LAN or WAN.

DCE Data circuit-terminating equipment.

DTE Data Terminal Equipment. The physical interface and link access procedures between DTE and data circuit-terminating equipment (DCE).

DTMF Dial tone multi-frequency, the signalling system used by PSTN. Refer to PSTN.

Downloading A user initiated transfer of data from a server to the user’s own workstation. Also used to classify the transfer of files from one system to another, usually to upgrade or revise system software.

EPROM Erasable programmable read-only memory. A chip whose memory can be erased and reused.

Ethernet A 10 Mbps baseband local area network protocol, compatible with IEEE 802.3 standards.