OSI/MHS Orientation Guide

Building Your Message Handling System
OSI/MHS Orientation Guide—424829-001
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What You Need to Know
The local operations server uses the same protocol and data formats as the remote
operations server but does not require messages between the user agent and the message
store to traverse the network or the OSI stack. For instance, a local user agent could
provide low-cost, asynchronous X.400 connections to workstations not equipped to run
complete remote user agent and OSI software.
Compaq offers a procedural interface for developing local user agents in either C or
TAL (the Compaq proprietary programming language). The interface is a
straightforward implementation of the P7 protocol and relies on the application to
encode and decode messages; therefore, it is reasonably simple to base a local user agent
on an existing remote user agent.
What You Need to Know
To develop an LUA, you need to be familiar with the following topics:
•
The C or TAL programming language
•
Fundamental NonStop programming concepts, including how to write fault-tolerant
applications if required
•
The P7 protocol, its data structures, and the structure of operations defined for the
remote operations service
•
The components of the P7 API, and how to incorporate them into your program
•
The syntax and semantics of P7 API procedure calls, including protocol data formats
•
How to use Abstract Syntax Notation 1 (ASN.1) for encoding and decoding protocol
data, and how to use an ASN.1 tool if you plan to use one
Figure 1-9. Integrating a Local User Agent (LUA) With OSI/MHS
009CDT .CDD
Message
Store
MTA
P1
Message Relay Process
+ Reliable Transfer Service
MTA
MS
MRP
RTS
OSI/AS
OSI/TS
TLAM X25AM
P1
MTA
LO
LUA
P7
API
I/O Device Protocol
(Guardian 90 I/O
Process)