NBT Manual

Glossary
NBT Manual—424773-001
Glossary-15
packet
packet. The unit of data sent across a packet switching network. While some Internet
literature uses it to refer specifically to data sent across a physical network, other
literature views the Internet as a packet switching network and describes IP datagrams as
packets.
Packet Internet Groper (PING). The name of a program used in the Internet to test the
reachability of destinations by sending them an ICMP echo request and waiting for a
reply. The term has survived the original program and is now used as a verb, as in
“please ping host A to see if it is alive.”
packet switching. A technique in which messages are broken into smaller units, called
packets, that can be individually addressed and routed through the network. The
receiving-end node ascertains whether all the packets are received and in the proper
sequence before forwarding the complete message to the addressee.
PCT. A Compaq program that runs on an IBM-type PC with the MS-DOS operating system,
and emulates a 6530 terminal.
PDN. See Public Data Network (PDN)
.
physical interface (PIF). The hardware components that connect a system node to a
network.
physical layer. Layer 1 in the OSI Reference Model. This layer establishes the actual
physical connection between the network and the computer equipment. Protocols at the
Physical Layer include rules for the transmission of bits across the physical medium and
rules for connectors and wiring.
PIF. See physical interface (PIF)
.
PING. See PING
.
port address. For X25AM lines, the logical port number used to specify the address of the
connection to the X.25 network. For TLAM lines, the address used by TLAM to specify
the address of the connection to a LAN controller.
predefined value. A commonly used value—for instance, a value for a token or a field in a
token—that is given a name in a set of definition files.
process. A running entity that is managed by the operating system, as opposed to a program,
which is a collection of code and data. When a program is taken from a file on a disk
and run in a processor, the running entity is called a process.
programmatic command. In DSM, a command issued by a program rather than by a human
operator. Compare interactive command
.