AMHS Storage, Delivery and Archiving

An AMHS deployment has a number of requirements for message storage and archiving. This page describes the various capabilities that Isode provides as a part of its AMHS solution, and shows how these can be used to meet various requirements in the context of Isode's AMHS Architecture.

Message Delivery

Isode's X.400 Message Switching product, M-Switch X.400, provides two options for delivering messages to end users:

Use of X.400 P3, to directly deliver to an application. This is suitable for a large ATC or ATM application which provides its own robust storage.
Use of an X.400 Message Store (M-Store X.400) which provides reliable message storage, and is suitable for AMHS clients which do not provide reliable storage.

Message Switch Archiving

M-Switch X.400 provides message archiving, that meets the ICAO requirements. This will be used to archive switched messages for 30 days or longer.

The archive may also be used to archive submitted and delivered messages, rather than having the AMHS client application do this. M-Switch X.400 records and archives submission and delivery information associated with messages, so all necessary information is archived. The advantages of using M-Switch X.400 to do this "end point" archiving are:

It is an integrated and efficient large scale archiving system.
It can be used in conjunction with both P3 and P7 delivery.
Archiving is done in one place to support multiple AMHS applications.
Archiving is performed on a managed central system.
User modification is not generally possible, and so it is suitable for audit purposes.

Direct Delivery (X.400 P3)

X.400 P3 is used to directly deliver to an application. This is suitable for a large ATC or ATM application which provides its own robust storage. It gives an efficient integration between the end application and M-Switch X.400, without the need for any intermediate process. This integration is likely to be the best approach for large sites using high end AMHS applications.

Isode's AMHS Client API provides a simple means to integrate ATC or ATM applications to use X.400 P3 to connect to AMHS. The same API also allows X.400 P7 integration, so this can be provided as a client option.

Use of a Message Store (X.400 P7) as a Managed Delivery Channel

For simpler AMHS clients, it makes sense to use an X.400 Message Store. This might be a Web client or a desktop application. The basic model of operation is that M-Store X.400 operates as a reliable, managed delivery channel. A client will retrieve a message, do necessary processing work, and then delete the message when it is processed. This approach has a number of advantages:

It makes things easier for the client developer.
If the client crashes or otherwise fails part way through processing a message, processing can be continued on another client, as the message is reliably stored on the server.
It is straightforward to support a scenario where a message may be processed by different people at different locations. Any of them can access the message in the message store (whereas with P3, the message has to be delivered to a specific application).

A Message Store will typically be used in systems where overall load is lighter. In this situation, use of M-Store X.400 gives additional advantages, as it is a part of the operator managed messaging infrastructure. While messages are in the message store, they can be monitored and tracked by the system operators. In the event of a message not being processed in a timely fashion, it can be non-delivered or redirected, either automatically after a period of time or by the operator. This enables operators to ensure that all messages are processed in a timely manner. In this type of scenario, this is a significant advantage of using a Message Store, as it prevents a message getting delivered to an AMHS application, and then not being processed.

Isode's M-Store X.400 and AMHS Client API are ideal for supporting this scenario.

Message Storing and Archiving in a Message Store

In the basic AMHS Message Store model described above, the Message Store is used for short term managed storage of messages being delivered. M-Store X.400 is a general message store, and may also be used for longer term storage by the AMHS client. This might be done:

To hold messages for a short period (e.g., a few hours), while they may still be of operational interest to the AMHS Client.
As an archive of delivered messages, held for 30 days or longer. This is appropriate for moderate volumes of messages, and where it is acceptable for the archive to be under user control.