TCP/IPv6 Migration Guide

Glossary
HP NonStop TCP/IPv6 Migration Guide—524524-004
Glossary-16
PDN
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 Packet Internet Groper (PING).
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.
preferred address. An address assigned to an interface whose use by upper layer
protocols is unrestricted. Preferred addresses may be used as the source (or
destination) address of packets sent from (or to) the interface.
preferred lifetime. The length of time that a valid address is preferred (that is, the time until
deprecation). When the preferred lifetime expires, the address becomes deprecated.
prefix. A bit string that consists of some number of initial bits of an address.
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.
protocol. A formal description of message formats and the rules two or more machines
must follow to exchange those messages. Protocols can describe low level details of
machine-to-machine interfaces (for example, the order in which the bits from a byte are
sent across a wire), or high-level exchanges between application programs (for
example, the way in which two programs transfer a file across the Internet). Most
protocols include both intuitive descriptions of the expected interactions as well as
more formal specifications using finite state-machine models.
Public Data Network (PDN). A network with data communications services available to any
subscriber.
Request for Comments. he name of a series of notes that contain surveys, measurements,
ideas, techniques, and observations, as well as proposed and accepted Internet
protocol standards. RFCs are edited but not referenced. They are available across the
Internet.