Introduction to Networking for NonStop S-Series Servers

Glossary
Introduction to Networking for HP NonStop S-Series Servers—520670-005
Glossary-17
Physical Layer
Physical Layer. Layer 1 of the Open Systems Interconnection (OSI) Reference Model. This
layer establishes the physical connection between the network and the computer
equipment. Protocols at the Physical Layer include rules for transmission of bits across
the physical medium and rules for connectors and wiring.
physical unit (PU). An entity in an IBM Systems Network Architecture (SNA) network,
responsible for the physical configuration of a node. Often identified with the node
itself; for instance, a host is a PU type 5.
point-to-point. Transmission of data directly between two points, without the use of any
intermediate terminal or computer. See also multipoint.
port. (1) A data channel that connects to other devices or computers. (2) A connector to
which a cable can be attached. The system transmits and receives data or requests
through ports on ServerNet adapters and processor multifunction (PMF) customer-
replaceable units (CRUs). A port is also called a connector. (3) The entrance or
physical access point (such as a connector) to a computer, multiplexer, device, or
network where signals are supplied, extracted, or observed.
Presentation Layer. Layer 6 of the Open Systems Interconnection (OSI) Reference Model,
responsible for accommodating differences in data representation between
communicating systems.
primitive. The smallest unit of action that can be requested of a protocol layer, or the
smallest unit of response.
procedure. A functionally separate block of machine instructions; part of a program. A
procedure is usually invoked by a statement called a procedure call.
process. A unique execution of a program. The NonStop Kernel operating system is a
collection of processes cooperating by using a common message system.
process pair. Two processes running the same program: a primary process that is active,
and a secondary, backup process (in another processor) that is ready to take over if
the primary process fails. See also NonStop.
profile. A disk file containing modifiers and default values. On NonStop S-Series servers, a
profile is required when configuring a device. HP provides profiles for the different
types of Expand line-handler processes. You can create your own customized profile
using the SCF interface to the WAN subsystem (ADD PROFILE command). You can
also alter profile modifier values for a particular device using the SCF interface to the
WAN subsystem (ADD DEVICE and ALTER DEVICE commands). Profiles are
provided on NonStop S-Series servers only.
programmatic. Used by programs, rather than by human operators.
protocol. The set of rules governing the operation of communicating entities.