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Glossary
Glossary-73160-A2-GB21-50 January 1997
PAP Password Authentication Protocol.
parity A way of checking data accuracy by counting the number of bits that have a value
of one.
payload The information bits in a frame.
PBX Private Branch Exchange. Telephone switching equipment dedicated to one
customer. A PBX connects private telephones to each other and to the public
network.
PC Personal computer. In this document, references to a PC imply an IBM PC or an
IBM-compatible PC.
PDU Protocol Data Unit. Used when adding routes in the Internet.
PDV Pulse Density Violation. The number of “ones” (marks, pulses) is not adequate for
the line requirement.
Perf branch Performance Report branch of the DSU/CSU menu tree.
PLB Payload Loopback. Loops the received signal on the network interface back to the
network after it has passed through the framing circuity of the DSU/CSU.
port An access point for data entry or exit.
PORT (1–4) interface The synchronous data port interface on the DSU/CSU.
POWER connector The power input connector on the DSU/CSU.
power-up self-test A test that checks most hardware components when power is applied to the device
or a reset is initiated.
PPP Point-to-Point Protocol. A link layer protocol used by SNMP.
PRBS Psuedo-Random Bit Sequence. A test pattern containing any possible combination
of digital ones and zeros for a given string length.
PRM Performance Report Message. A message indicating performance data such as
errored seconds, unavailable seconds, etc.
protocol A set of rules that determines the behavior of functional units in achieving
communication.
PSTN Public Switched Telephone Network.
Ptrns branch Test Patterns branch of the DSU/CSU menu tree.
pulse density A measure of the number of “ones” (marks, pulses) in relation to the total number
of bits transmitted.
QRSS Test Quasi-Random Signal Source Test. A test pattern simulating a random pattern of
digital ones and zeros used to simulate normal transmission.
RAM Random-access memory. Read/write memory that is volatile and loses its contents
when power is removed.
register A part of the device’s memory that holds stored values.
Rel branch Release branch of the DSU/CSU menu tree.
reset A reinitialization of the DSU/CSU that occurs at power-up or in response to a reset
command.
RFC Request for Comments. The set of documents that describes the standard
specifications for the TCP/IP protocol suite.
RIP Routing Information Protocol. A protocol used to add routes in the Internet.
RJ48C An 8-position modular connector.