IBM 2220 Nways 300, Service Manual

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time. It is obtained by dividing the number of packets
lost in transmission by the total number transmitted.
packet transfer mode (PTM). The native transfer
mode of the NBBS architecture. PTM divides the traffic
into packets of variable length.
PBX. Private branch exchange.
PCM. Pulse code modulation.
PCR. Peak cell rate.
PDH. Plesiochronous digital hierarchy.
permanent virtual circuit (PVC). A virtual circuit that
has a logical channel permanently assigned to it at
each item of data terminal equipment. It is activated by
a program or by a network operator request.
plesiochronous. Refers to transmission at a nominal
bit rate where the source and destination are controlled
by different clocks. The bit rates are nearly the same.
PLP. Packet layer protocol.
PNP. Private numbering plan.
port. See logical port.
port adapter. In an Nways Switch, a module that
provides access services to one or more port lines.
Each port adapter is associated with a line interface
coupler (LIC).
port line. A communication line that connects a device
on user premises to an Nways Switch and serves as a
port to the 2220 network. Port lines have different
protocols and interfaces.
position. When configuring an Nways Switch, the
position parameter indicates the line attachment number
on the LIC module (1 to 8, depending on the LIC type).
potential connection. A predefined connection
through a 2220 network between two HDLC, CES, or
frame-relay devices.
PPP. Point-to-point protocol.
PRA. Primary Rate Access.
private branch exchange (PBX). A switching system
located on a user premises that relays inside lines
(extensions) and provides access to the public
telephone network.
PRS. Primary reference source.
PSDN. Packet switched data network.
PSN. Public switched network.
PSTN. Public switched telephone network.
PTF. Program temporary fix.
PTM. Packet transfer mode.
PTNX. Private telecommunications network exchange.
pulse code modulation (PCM). A standard adopted
for the digitalization of analog voice signals. In PCM,
voice is sampled at a rate of 8 kHz and each sample is
coded in an 8-bit frame.
PVC. Permanent virtual circuit.
Q signaling (QSIG). An international standard for
signaling procedures in private telecommunication
networks. It applies to the PBX-to-Nways Switch
interface, which is called the Q reference point.
QoS. Quality of service.
QSIG. Q signaling.
quality of service (QoS). In a 2220 network, a set of
parameters that guarantees the characteristics of a
connection, mainly its end-to-end delay, delay variation,
and packet loss tolerance.
RABM. Router and Bridge Manager.
rack. A metallic structure, with a standard 19-inch
width, that houses the hardware elements of an Nways
Switch, that is, logic subrack with modules, fan boxes,
and power units.
When configuring an Nways Switch, the rack parameter
indicates the 2220 Model (rack A is the Model 300 or
500, and rack B is the Model 501).
RDI. Remote defect indication.
real-time processing. Refers to the manipulations of
data that are required, or generated, by certain process
while the process is in operation. Usually, the results
influence the process and, perhaps, related processes.
remote user console. A station running OS/2,
TCP/IP, and Nways Switch Resource Control. It can be
connected to the NAS of an Nways Switch to remotely
control and service it.
resource. In an Nways Switch, a hardware element or
a logical entity created by the Control Program.
Adapters, modules, and line attachments are examples
of physical resources. Control points, logical trunks,
logical ports, and network interfaces are examples of
logical resources.
resource profile. A record of the characteristics of an
Nways Switch resource. It includes (for example) the
Glossary
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