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GLOSSARY 441
intelligent hub See managed hub.
IP Internet Protocol. The TCP/IP standard protocol that defines the IP
datagram as the unit of information passed across an Internet. IP provides
the basis for connectionless packet delivery service.
IP address The address used by devices on the network to establish their unique
identity. IP addresses are composed of four fields separated by dots. Each
field is an 8-bit number (0 through 255). IP addresses can be permanently
assigned, or they can be temporarily assigned by DHCP
.
IP telephony Technology that allows voice, data, and video to be transmitted over
IP-based networks.
ISDN Integrated Services Digital Network. An international telecommunications
standard for transmitting voice, video and data over digital lines running
at 64 Kbit/s. ISDN uses B channels, or “bearer” channels, to carry voice
and data. It uses a separate D channel, or “delta,” channel for control
signals to the telephone company computer.
ITU International Telecommunication Union. An international standards
organization for telecommunications.
jitter The variation in latency (waiting time) for different packets on the
network. For real time data such as voice transmission, jitter must be kept
to a minimum.
key mode A telephone system operating model in which each telephone in the
system has buttons for each available outside line. Also known as a
square plan or a direct system inward access (DISA) system. See also
hybrid mode
.
LAN local area network. A communications system that links computers,
printers, and other devices. LANs allow users to communicate and share
resources like hard disk storage and printers. Devices linked by a LAN may
be on the same floor or within a building or campus.
LAN segment A section of a local area network that is used by a particular workgroup or
department and separated from the rest of the LAN by a bridge, router or
switch.
LAN switch A network device that connects stations or LAN segments, also known as
a frame switch.