Glossary-25
PBX, private branch exchange
A privately owned phone system installed within the premises of an
organization. It allows communication among users within the organization,
as well as between those users and the outside world. It differs from a key
telephone system in that the user must dial an access number, such as 9, to
get an outside line.
PDN, public data network
A network established and operated by a Post Telephone, and Telegraph
Authority (PTT), common carrier, or private operating company for the
specific purpose of providing data communication services to the public.
permanent virtual circuit
See
PVC.
pointtopoint
A communications circuit or transmission path connecting two points. In the
Integration unit that connection can be force connected (dedicated pointto
point) or switched (switched pointtopoint).
port
A physical connector on the back of the Integration unit. Also, an interface
capable of attaching to a device for communications with another device.
Power Plus
Redundant power supply kit available for any 5slot Integration unit. Power
Plus provides two separate power supplies which share the load equally;
should one power supply fail, the other assumes the full load.
primary interconnect link
An interconnect link associated with a secondary link.
protocol
Any standard method of communicating over a network (LAN or WAN).
PTT, Post, Telephone, and Telegraph Authority
A government agency that functions as the communications common carrier
and administrator in many areas of the world.
PVC, permanent virtual circuit
1) A logical link, whose endpoints and class of service are defined by network
management. 2) (In frame relay) Analogous to an X.25 permanent virtual
circuit, a PVC consists of the originating frame relay network element
address, originating data link control identifier, terminating frame relay
network element address, and termination data link control identifier
(DLCI). Originating refers to the access interface from which the PVC is
initiated. Terminating refers to the access interface at which the PVC stops.
Many data network customers require a PVC between two points.
