X25AM Programming Manual

Glossary
X25AM Programming Manual—527201-001
Glossary-7
parity checking.
parity checking. Testing a group of bits to determine whether the number of ones in the
group is odd or even.
PDN. See public data network (PDN).
permanent virtual call (PVC). Association between two entities for packet exchange. Set
up by a call, it remains in place in the data-transfer phase until terminated. A call
consists of data transfer and does not require call set-up and call clearing physical
level. X.25 protocol description for the physical link between the network and the
computers, terminals, or other devices.
port number. Number assigned to a subdevice to link an address to a specific subdevice.
Sometimes referred to as a subaddress.
process. While a program on a NonStop system is being run, it is called a process.
program. Set of coded instructions residing on a disk.
protocol. Set of rules for assembling, sending, and receiving data.
PTP protocol. Process-to-process protocol. For X25AM, is used by the X25AM process
when it exchanges data with a remote device.
public data network (PDN). A network providing (among other possible services)
packetswitching services to the public.
PVC. See permanent virtual call (PVC).
QLLC. Qualified Logical-Link Control protocol. A link-level IBM protocol serving as an X.25
interface for attaching SNA devices to packet-switched networks.
REJ. Reject. Link-level control frame or packet-level packet. As a packet, it requests the
retransmission of data.
restart packet. Packet sent by the network when a call is restarted.
RNR. Receiver not ready. Link-level frame or packet-level packet. As a packet, it
acknowledges the receipt of data and requests that packet transmission be halted.
RPOA. Registered private operating agency. Network provider providing some degree of
public service.
RR. Receiver ready. Link-level frame or packet-level packet. As a packet, it acknowledges
the receipt of data and requests that packet transmission continue.
RS-232. An industry standard defining the physical characteristics of the cable and 25-pin
connectors used for connecting a DTE and a DCE.
RS-422/449. An industry standard defining the physical characteristics of the cable and the
37-pin and 9-pin connectors used for connecting a DTE and a DCE.