NS3000/iX NMMGR Screens Reference Manual - Edition 8 (36922-90038)

338 Glossary
Glossary
depending on the device and how
it is opened by the controlling
program.
protocol A set of rules that
enables two or more data
processing entities to exchange
information. In networks,
protocols are the rules that
govern each layer of network
architecture. They define which
functions are to be performed and
how messages are to be
exchanged.
PSN Packet-Switching Network.
Any data communication network
in which data is disassembled
into packets at a source interface
and reassembled into a data
stream at a destination interface.
A public PSN offers the service to
any paying customer.
PSS Packet-Switching System.
The national public PSN of the
United Kingdom.
PVC Permanent Virtual Circuit.
A permanent logical association
between two physically separate
DTEs that does not require call
set-up or clearing procedures.
PXP See packet exchange
protocol.
Q
Q bit Qualified bit. When set in
DATA packets the Q bit signifies
that the packet’s user data is a
control signal for the remote
device, not a message for its user.
QuickVal A software program
that tests whether Network
Services are operating correctly
between nodes.
R
RDBA Remote data base access.
A network service that allows
users to access data bases on
remote nodes.
reachable network A network
that can be accessed (with
additional internet hops possibly
required) by a particular gateway.
remote connect device An
asynchronous device that is
indirectly connected to a DTC
through a modem and telephone
hook-up or through a PAD.
remote node Any network node
that is physically separate from
the node you are currently using
or referring to.
retransmission count (N2) The
maximum number of times a
frame will be retransmitted
following the expiration of the
Retransmission Timer, T1.
retransmission timer (T1) The
length of time that a transmitter
will wait for an acknowledgment
from a destination address before
attempting to retransmit a frame.
When choosing this value, factors
like the line speed and maximum
frame size should be taken into
account.