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private branch exchange (PBX). A private telephone
exchange for transmission of calls to and from the
public telephone network.
problem determination. The process of determining
the source of a problem; for example, a program
component, machine failure, telecommunication
facilities, user or contractor-installed programs or
equipment, environmental failure such as a power loss,
or user error.
program temporary fix (PTF). A temporary solution or
bypass of a problem diagnosed by IBM in a current
unaltered release of the program.
protocol. (1) A set of semantic and syntactic rules that
determine the behavior of functional units in achieving
communication. (I) (2) In Open Systems
Interconnection architecture, a set of semantic and
syntactic rules that determine the behavior of entities in
the same layer in performing communication
functions. (T) (3) In SNA, the meanings of, and the
sequencing rules for, requests and responses used for
managing the network, transferring data, and
synchronizing the states of network components.
Synonymous with
line control discipline
and
line
discipline
. See
bracket protocol
and
link protocol
.
protocol data unit (PDU). A unit of data specified in a
protocol of a given layer and consisting of protocol
control information of this layer, and possibly user data
of this layer. (T)
R
Rapid Transport Protocol (RTP) connection. In
high-performance routing (HPR), the connection
established between the endpoints of the route to
transport session traffic.
reachability. The ability of a node or a resource to
communicate with another node or resource.
read-only memory (ROM). Memory in which stored
data cannot be modified by the user except under
special conditions.
real-time processing. The manipulation of data that
are required, or generated, by some process while the
process is in operation. Usually the results are used to
influence the process, and perhaps related processes,
while it is occurring.
reassembly. In communications, the process of putting
segmented packets back together after they have been
received.
receive not ready (RNR). In communications, a data
link command or response that indicates a temporary
condition of being unable to accept incoming frames.
receive not ready (RNR) packet. See
RNR packet
.
received line signal detector (RLSD). In the EIA 232
standard, a signal that indicates to the data terminal
equipment (DTE) that it is receiving a signal from the
remote data circuit-terminating equipment (DCE).
Synonymous with
carrier detect
and
data carrier detect
(DCD)
.
Recognized Private Operating Agency (RPOA). Any
individual, company, or corporation, other than a
government department or service, that operates a
telecommunication service and is subject to the
obligations undertaken in the Convention of the
International Telecommunication Union and in the
Regulations; for example, a communication common
carrier.
reduced instruction-set computer (RISC). A
computer that uses a small, simplified set of frequently
used instructions for rapid execution.
remote. (1) Pertaining to a system, program, or device
that is accessed through a telecommunication line. (2)
Synonym for
link-attached
. (3) Contrast with
local
.
remote bridging. The function of a bridge that allows
two bridges to connect multiple LANs using a
telecommunication link. Contrast with
local bridging
.
Remote Execution Protocol (REXEC). A protocol that
allows the execution of a command or program on any
host in the network. The local host receives the results
of the command execution.
Request for Comments (RFC). In Internet
communications, the document series that describes a
part of the Internet suite of protocols and related
experiments. All Internet standards are documented as
RFCs.
reset. On a virtual circuit, reinitialization of data flow
control. At reset, all data in transit are eliminated.
reset request packet. In X.25 communications, a
packet transmitted by the data terminal equipment
(DTE) to the data circuit-terminating equipment (DCE) to
request that a virtual call or a permanent virtual circuit
be reset. The reason for the request can also be
specified in the packet.
ring. See
ring network
.
ring network. (1) A network in which every node has
exactly two branches connected to it and in which there
are exactly two paths between any two nodes. (T) (2)
A network configuration in which devices are connected
by unidirectional transmission links to form a closed
path.
ring segment. A section of a ring that can be isolated
(by unplugging connectors) from the rest of the ring.
See
LAN segment
.
Glossary 707