OSI/MHS P7 Application Programmatic Interface (P7 API) Manual

Glossary
OSI/MHS P7 Application Programmatic Interface (P7 API) Manual—424825-001
Glossary-19
P2 message
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 MT-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.
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.
PDU store. The database that stores messages in an X.400 system. A PDU store consists of a
data file and a log file. Each MR, MS, RS, and LO group has its own PDU store.
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.
Port Access Method (PAM). A Compaq communications subsystem that provides an
independent interface to allow applications access to token-ring or Ethernet local area
networks (LANs) on Himalaya S-series servers. The PAM subsystem provides a port
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)