Civil Aviation

For over 20 years we have been providing critical software to civil aviation authorities across the globe, with roughly 90% of countries using Isode products in one way or another for their civil aviation needs.


Our approach

Across more than two decades we have been working closely with government and civil aviation authorities to keep their communications and data flowing.

Our software and servers are deployed alongside our partners networks to provide comprehensive Air Traffic Messaging Handling Systems (AMHS).

Civil Aviation

AMHS Messaging

Ground to Ground Communication for Civil Aviation

The aviation industry has adopted AMHS (Air Traffic Services (ATS) Message Handling Services) to support ground to ground communications for services such as flight plans and meteorological data. AMHS based systems replace those based on the older AFTN and CIDIN based systems.

Hundreds of AMHS-based systems have now been deployed around the world, with a large majority of countries who have so far made the switch, using solutions from Isode partners that incorporate Isode servers and APIs.


ATN Directory

The Air Traffic Network (ATN) Directory is defined by the International Civil Aviation Authority as a part of the overall ATN specifications. A major goal of the ATN Directory is to support Aviation Messaging (AMHS).

Directory is a core element in Isode’s offering for the Civil Aviation market both as a core element in AMHS Messaging and to enable the Extended ATS Message Service.

AMHS provides a distributed message switching and storage infrastructure, to enable transfer of ATS messages, such as flight plans, NOTAM (Notice to Airman) and Meteorological information.

The AMHS service is accessed by users, using AMHS terminals, and applications (such as Meteorological applications), in order to exchange ATS messages. AMHS Terminals and AMHS Applications connect to the AMHS infrastructure using X.400 protocols.

What Isode Provides

  • M-Switch X.400: an X.400 MTA (Message Transfer Agent) that provides the core message switching services and connects to external systems.
  • M-Store: a robust X.400 Message Store for storing messages.
  • M-Vault: an LDAP/X.500 Directory Server which is used to configure the Isode AMHS products and may also provide an independent directory service.
  • An X.400 Client API enabling the development of AMHS client applications connecting to M-Switch using X.400 P3 or to M-Store using X.400 P7. This multi-protocol approach allows applications to either directly access M-Switch X.400, or to go via M-Store X.400 if message storage is needed.
  • An X.400 Gateway API enabling the development of AMHS Gateways to AFTN or CIDIN following the specifications in the ICAO SARPs for provision of an MTCU (Message Transfer and Conversion Unit).
  • An X.400 demonstration user agent, Xuxa, a Java GUI to help test and demonstrate and test Isode server products an APIs.

Solutions based on the Isode AMHS products offer a number of benefits including full ICAO SARPs Conformance (Isode’s solution is the first to be conformant to the Extended ATS Message Service, and the first to provide a conformant ATN Directory), Fail-over clustering support for all components and Directory based configuration management providing flexible client/server configuration.

AMHS Architecture


AFTN Transition & Co-Existence

As ground to ground messaging moves to AMHS, it is important that full interoperability is maintained with existing AFTN systems. This is achieved by the use of an AFTN/AMHS gateway, formally known as an MTCU (Message Transfer and Conversion Unit). MTCUs are critical to enabling full connectivity while both AFTN and AMHS are being used. MTCUs are available from Isode partners.

The Extended ATS Service & ATN Directoy

AMHS defines two services:

  1. The Basic ATS Service, which provides functionality equivalent to AFTN.
  2. The Extended ATS Service, which provides additional services and functions, including security based on digital signatures; binary attachments; large attachments.

The Isode servers and APIs provide full support for both the Basic and Extended ATS Service. A key element of the Extended ATS Service is use of the ATN Directory. Isode provides a full set of products for constructing an ATN Directory solution.

ATN Directory is a core element in Isode’s offering for the Civil Aviation market, both as a core elemnt in AMHS Messaging and to enable the extended ATS Message Service.

What Isode Provides

  • M-Vault: an LDAP/X.500 Directory Server which is the core component of an ATN Directory. It has full compliance to the ICAO DOC 9880 specifications for ATN Directory products, and supports chaining, replication and security features.
  • Sodium-Sync: enables synchronization between directory servers and other data sources such as files and databases
  • Directory Client API: used to connect AMHS applications to M-Vault X.500 using X.500 DAP (Directory Access Protocol). This allows lookup of information such as Certificates and AMHS parameters, and supports mappings between AFTN addresses and X.400 O/R Addresses.

Isode’s mature and robust product have been deployed for many years in demanding operational environments, including within AMHS solutions used by over 100 countries. Isode’s directory is fully ICAO compliant with excellent security features (including strong authentication for all directory protocols and signed operations) and comprehensive GUIs for data and operational management.

ATN Directory Architecture

The ATN Directory holds data in a hierarchy containing information about CAAs (Civil Aviation Authorities) and other ATN users. Data in the ATN Directory is available to users worldwide.


The diagram above shows how the ATN Directory is provided by multiple directory servers, and can support AMHS and non-AMHS applications utilizing data in the ATN Directory. Directory data will be stored in a server operated by the data owner. This model allows a CAA to start with a single directory server containing the CAA’s own data for local use. This isolated server can then be connected to other servers using one or both of two mechanisms:

  • Chaining, where one server knows about data held in another, and can connect to that server in order to retrieve data for an end user or application.
  • Replication, where selected data is copied to another server, thus making it available locally to users of that server.

This interconnection will allow incremental building of a distributed global service.

How AMHS uses the ATN Directory

AMHS, as described in AMHS Messaging page, requires use of the ATN Directory in order to provide the Extended ATS Message Service. This provides the following benefits to the user:

  • Recipient validation prior to and after message submission.
  • Access to the end user X.509 certificate.
  • Access to information about (potential) message recipients.
  • Determining AMHS capabilities (e.g., maximum message size supported), and in particular determining if the Extended ATS Service is supported by the message recipient. This allows an originator to determine the service level a recipient supports, and to only send messages with Extended ATS Service capabilities to recipients that can correctly handle this.

An additional benefit of using the ATN Directory is to manage address mapping between X.400 OR Addresses and AFTN addresses. This mapping can be used by AFTN/AMHS Gateways, and also to enable users to enter AFTN addresses and have them automatically converted. Holding this mapping in the directory enables the same mapping information to be easily used by all users and servers that need it, and to be conveniently managed in a machine oriented format. Isode’s ATN Directory API provides simple calls to enable applications to easily use this mapping.

Our [ATN directory vision] whitepaper sets out the benefits of using an ATN Directory in support of AMHS and ground to ground messaging communication, and explains how this directory could be deployed in conjunction with AMHS.

Data Management

The ATN Directory holds data that needs to be managed. The tool to do this is often referred to as an ADUA (Administrative Directory User Agent). Sodium (Secure Open Directory, User and Identity Manager) is Isode’s ADUA. Sodium provides a flexible GUI for data administration.

In some cases data will be managed indirectly, for example mapping data may be obtained from the European Directory Service (EDS). In this case, data will simply be replicated in, using X.500 DISP.

Mapping data may also be obtained as CSV files. Isode provides scripts to enable conversion of this data to LDIF, which can then be loaded into the directory use Sodium or Sodium Sync.

Operational Management

The ATN Directory is critical infrastructure that is important in itself and as support for other applications. It is important to monitor servers for availability and correct operation. Although Isode provides two approaches to achieve this, the recommended approach is to use Isode’s M-Vault Console tool, which provides GUI monitoring of one or more M-Vault directory servers. M-Vault Console also has knowledge of directory replication and can monitor replication agreements from both ends. This is important to ensure that all servers are up to date with the most recent information.

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