The act of trimming down the Shortest Path Tree. This deacti-
vates interfaces that do not have group participants.
Packet Switch Exchange: The X.25 term for a switch.
packet-switched network: Any network that uses packet-switching
technology. Also known as packet-switched data network (PSDN). See also:
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.
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.
permanent virtual path: A virtual path made up of PVCs. See also: PVC.
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.
Per-VLAN Spanning Tree: A Cisco proprietary implementation of
STP. PVST uses ISL and runs a separate instance of STP for each and
Per-VLAN Spanning Tree+: Allows CST information to be passed
Quality of Service: A set of metrics used to measure the quality of
transmission and service availability of any given transmission system.
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.
A quality of service process that allows packets to be forwarded
from the router based on administratively defined parameters. This may be
used for time-sensitive protocols, such as SNA.
Copyright ©2001 SYBEX , Inc., Alameda, CA