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Glossary
212 Interphase Corporation
PMC (PCI Mezzanine Card) A daughtercard form factor implemen-
tation of the PCI bus specification.
POTS (Plain Old Telephone Service) Conventional voice grade
service and cabling infrastructure.
PPP (Point-to-Point Protocol) A dial-up protocol that allows a
computer to use TCP/IP networking to connect remote access devices,
such as modems, to the Internet or other TCP/IP based networks.
PPP/MP (Point-to-Point Protocol/Multilink Protocol) See Multi-link
PPP.
PRI (Primary Rate Interface) A type of ISDN service that offers 23
B-channels at 64 Kbps and one D-channel at 64 Kbps (23B+D). In
Europe, PRI provides for 30 B-channels and two D-channels
(30B+1D).
Private Line Synonym for a leased line. Dial voice line that does
not terminate at the voice private automatic branch exchange or that
does not appear on other sets in a key system.
Protocols A set of rules that define how different computer systems
and other devices interoperate with each other.
PSTN Public Switched Telephone Network.
PVC (Permanent Virtual Circuit) A logical link whose endpoints
and class of service are defined by network management.
For 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 net-
work element address, and termination data link control identifier.
Originating refers to the access interface from which the PVC is initi-
ated. Terminating refers to the access interface at which the PVC stops.
Many data network customers require a PVC between two points.
QLLC (qualified logical link control) An X.25 protocol that allows
the transfer of data link control information between two adjoining
SNA nodes that are connected through an X.25 packet-switching data
network. The QLLC provides the qualifier Q bit in X.25 data packets
to identify packets that carry logical link protocol information.
Q.921 This is the link layer protocol for ISDN.
Q.931 This is the network layer protocol for ISDN. Q.931 was
developed for out-of-band call control.
RAI (Remote Alarm Indication) PRI alarm, also known as Yellow
signal. This alarm indicates a carrier failure.