OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide

Glossary
OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide—424822-001
Glossary-21
P2 protocol
P2 protocol. The X.400 interpersonal message (IPM) user agent protocol, which defines the
format by which one user agent (UA) sends an interpersonal message (IPM) to one or
more other UAs.
P2 message. An X.400 message that 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.
P3 protocol. The X.400 message submission and delivery protocol, which defines a standard
for the submission and delivery of messages and the interaction of UAs and MTAs.
P7 protocol. The X.400 protocol defining access to the message store by remote or local user
agents.
package. A set of GPI object classes that are grouped together because they are functionally
related and defined in the same specification. For example, the MH 88 package consists
of the message handling classes defined in the XAPIA specification.
packet switching. A technique in which messages are broken into smaller units, called
“packets,” which can be individually addressed and routed through the network. The
receiving-end node ascertains that all the packets are received and in the proper
sequence before forwarding the complete message to the addressee.
PAM. See Port Access Method.
password server. An application process that provides security services at the MTA-MTA or
UA-MS boundary. Such an application uses either the MTA-bind or the MS-bind
password server interface of OSI/MHS. The master password server provided with
OSI/MHS is an example of a password server.
PDAU (physical delivery access unit). A commonly-used type of access unit (AU) within
an EDI messaging system as defined in CCITT Recommendation X.435. The PDAU
provides the ability to send messages to EDIMS users (recipients) through a physical
delivery system (PDS). Other types of access units (for example, facsimile machines)
may be the subject of future CCITT standards.
PDU (protocol data unit). An information unit that contains control and address information
and possibly data, and is exchanged between peer entities. Two types of PDUs relevant
to X.400 are:
PDU ID. An identifier generated by OSI/MHS for internal use. A PDU ID is not the same as
the MPDU ID defined by X.400.
MPDU (message PDU) Information exchanged between message handling
systems (used by OSI/MHS)
APDU (application PDU) Information exchanged between OSI Application Layer
entities (used by OSI/AS)