Glossary
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PSE
packet switching exchange: The X.25 term for a switch.
PSN
packet-switched network: Any network that uses packet-switching
technology. Also known as packet-switched data network (PSDN). See also:
packet switching.
PSTN
public switched telephone network: Colloquially referred to as
"plain old telephone service" (POTS). A term that describes the assortment
of telephone networks and services available globally.
PVC
permanent virtual circuit: In a Frame Relay network, a logical con-
nection, defined in software, that is maintained permanently. Compare with:
SVC. See also: virtual circuit.
PVP
permanent virtual path: A virtual path made up of PVCs. See also: PVC.
PVP tunneling
permanent virtual path tunneling: A technique that links
two private ATM networks across a public network using a virtual path,
wherein the public network transparently trunks the complete collection of
virtual channels in the virtual path between the two private networks.
QoS
quality of service: A set of metrics used to measure the quality of
transmission and service availability of any given transmission system.
queue
Broadly, any list of elements arranged in an orderly fashion and
ready for processing, such as a line of people waiting to enter a movie the-
ater. In routing, it refers to a backlog of information packets waiting in line
to be transmitted over a router interface.
R reference point
Used with ISDN networks to identify the connection
between an NT1 and an S/T device. The S/T device converts the four-wire
network to the two-wire ISDN standard network.
RADIUS
Reverse Address Resolution Protocol: A protocol that is used to
communicate between the remote access device and an authentication
server. Sometimes an authentication server running RADIUS will be called a
RADIUS server.
RAM
random-access memory: Used by all computers to store information.
Cisco routers use RAM to store packet buffers and routing tables, along with
the hardware addresses cache.
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