OSI/MHS Administrative Utility (AU) Manual

Glossary
OSI/MHS Administrative Utility (AU) Manual—424826-001
Glossary-2
message
message. A communication, typically consisting of multiple, related data elements and
control information.
In X.400, an information object that consists of an envelope and its contents. The
envelope identifies the originator and the potential recipient of the message and
documents its path through the system.
message protocol data unit. See MPDU
message transfer agent. See MTA
message transfer system. See MTS
MPDU (message protocol data unit). A user message, a probe, or a delivery report. An
MPDU can contain other, subordinate PDUs.
MTA (message transfer agent). The functional component that routes X.400 messages
through an X.400 network. MTAs work together to transfer messages and deliver them
to the intended recipient; there can be multiple MTAs on the path between any two
users. In OSI/MHS, multiple message relay (MR) groups operate in parallel as a single
logical MTA.
MTS (message transfer system). The part of the message handling system that contains the
message transfer agents (MTAs) and that permits communication between user agents.
nondelivery report. A communication directed by a message transfer agent (MTA) toward
the originator of a message, indicating why the message could not be delivered to the
UA of its intended recipient, and including trace and diagnostic information.
Open Systems Interconnection/Message Handling System. See OSI/MHS
OSI/MHS (Open Systems Interconnection/Message Handling System). The Compaq
implementation of an X.400 message handling system for Compaq NonStop systems.
OSI/MHS subsystem. The set of all processes and files defined through the installation
procedure, and through SCF or management applications, to be part of an OSI/MHS
environment, under control of a specified MHS manager. There can be more than one
OSI/MHS subsystem on a Compaq NonStop system.
P1 protocol. The X.400 message transfer protocol, which defines the transfer of messages
between two message transfer agents (MTAs). (See the CCITT standards documentation
for X.411.)
P2 protocol. The X.400 interpersonal message protocol, which is defined as part of the
Interpersonal Messaging System (IPMS), and which consists of a heading followed by a
series of data blocks, called body parts. The heading contains the message originator,
recipients, and other service information. Each body part can contain a different form of
data, and messages can be nested within body parts. (See the CCITT standards
documentation for X.420.)