OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide

OSI/MHS Gateway Programmatic Interface (GPI) Programming Guide—424822-001
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Introduction
The Compaq Gateway Programmatic Interface (GPI) presents proprietary message
systems with a standard interface to X.400 networks (Figure 1-1).
There are two distinct types of GPI gateway: NORMAL and P1-EXIT. In the
NORMAL case, the GPI and a proprietary client program constitute a gateway between
the proprietary message system and the X.400 network. The P1-EXIT type of gateway
enables a proprietary client program to monitor traffic on the X.400 network.
The GPI service communicates with the X.400 network through a Message Transfer
Agent (MTA) that is part of a Compaq Open Systems Interconnection Message
Handling System (OSI/MHS) subsystem operating within the X.400 network.
This section is an overview of the GPI. It relates the GPI to X.400 and OSI/MHS. It
also provides a general description of GPI components and how they work. The
following topics are covered:
•
X.400 gateway APIs
•
Compaq GPI
•
Process Architecture
•
GPI operation
This section is most useful to you if you are already familiar with X.400 and OSI/MHS.
If you are not, you might want to first read Appendix C, Review of X.400 and
OSI/MHS.
X.400 Gateway APIs
To ease X.400 gateway development, standards groups defined a multi-purpose X.400
gateway application program interface (API). The API was first specified by the X.400
Application Program Interface Association (XAPIA) in June 1989. In September 1990,
the XAPIA and X/Open Company Limited specified a revised version.
XAPIA specifications provide message transfer agent (MTA) vendors a template for
their individual X.400 APIs. An MTA vendor can choose to implement all or any part of
the template.
Figure 1-1. A Gateway Links Two Networks
101CDT .CDD
Proprietary Message
System Gateway
X.400 Network
MTA
Client
GPI