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Glossary
Avaya P460 Reference Guide 207
PNNI
Private Network to Network Interface. The interswitch interface within a private
ATM domain. The PNNI trunking protocol for hierarchal ATM-layer routing and
QoS support.
POP
Post Office Protocol. Used to retrieve E-mail from a mail server. Most E-mail
applications use the POP protocol, although some can use the newer IMAP (Internet
Message Access Protocol). POP3, unlike earlier versions, can be used with or
without SMTP.
Port
A physical port is a connecting component that allows a microprocessor to
communicate with a compatible peripheral. A port is identified by a port number.
Protocol
A set of rules and conventions that governs how devices exchange data, especially
across a network. Low level protocols define the electrical and physical standards to
be observed, bit- and byte-ordering, the transmission, error detection, and
correction of the bit stream. High level protocols deal with data formatting,
including message syntax, terminal to computer dialogue, character sets, message
sequencing, etc.
Protocol Stack
A layered set of protocols which work together to provide a set of network
functions. Each intermediate layer uses the layer below it to provide a service to the
layer above.
PSTN
Public Switched Telephone Network. The collection of interconnected systems
operated by the various telephone companies and administrations around the
world.
PVC
Permanent Virtual Circuit. A permanent, virtual connection established by the
network management between an origin and a destination.
QoS
Quality of Service. A measure of performance for a transmission system that reflects
the system’s transmission quality and service availability. QoS is used mainly in
connection with ATM media.