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The ATN Directory
The ATN Directory is an Electronic Directory to support Air Traffic Communications systems. It is based on the ITU-T X.500 Series Recommendations, and has been extended to support the Aeronautical Telecommunications Network, its users and applications.
The basic Directory Services and Protocols defined by X.500 are designed to hold information about real world objects which need
to communicate with each other. The information for each object is held in a Directory Entry.
In essence, the directory emulates the services
currently provided by the paper telephone
directories (such as White
Pages, Yellow Pages
etc.), but in electronic form. In common personal/business applications, a directory
might contain such things as a person's or business organisation's telephone number,
fax numbers, postal addresses. These pieces of information are referred to as Attributes
of the objects that they describe.
The Directory concept is quite open and extensible:
- The objects may be persons, organisations, organisational units, computers, machines, countries
... In the Air Traffic Control arena, special objects have been defined which include ACCs, Aircraft, and
ICAO States, reflecting
Air Traffic Control requirements
- A set of Air Traffic Services attributes have been defined for use within the ATC Community. These include ACC Location codes, ATN Aircraft Identity, ATN Facility Identity, AMHS Addresses, AFTN Addresses …
In fact, as with the ‘Global Directory’ envisaged by the ITU-T
X.500 Recommendations,
the ATN Directory is intended to be a global, distributed and possibly replicated
database of ATN-specific object entries. This will allow each ANSP to
manage its own entries, whilst sharing and synchronising those entries with other
ANSPs.
Why does AMHS need an ATN Directory?
The main reasons for implementing an ATN Directory for AMHS are:
- AFTN addresses are different to AMHS addresses, so the
messaging gateways that connect AFTN and AMHS must translate between these different
forms. The translation process depends on address translation data which must be
globally synchronised. The ATN Directory may be used to distribute, update and synchronise
this address translation data.
- To allow lookup and browsing of ATC object entries by operational and administrative
staff.
- It can support the Public Key Infrastructure required to provide digital signature security
to AMHS and other applications
- It will allow more efficient and timely management of much of the data required
to operate the AMHS and the AFTN gateways.
Many of the AMHS implementations that have already been actually
commissioned by ANSPs do not yet use the AMHS Directory. There are several reasons for this:
- The definitions of the ATN Directory were only finally
stabilised during 2006, and implementations
are only now becoming available as products in the market
- The need for ATN Directory support when only a few ANSPs are actually conecting using AMHS is low,
because the AMHS can be managed relatively easily between pairs of ANSPs
- Those ANSPs that have implemented AMHS want to get wider operational experience
of the new AMHS technology before committing resources to implement the ATN
Directory. However, as the number of interconnected ANSPs rises, the difficulties
of management and co-ordination will grow exponentially, and this will lead to a
much more urgent requirement for support of the ATN Directory Services. The need will be evident soon.
The ATN Directory is a generally useful tool that may be configured to support many
more ATC operational and administrative tasks. However,
the AMHS use of the ATN Directory is the most immediate requirement. Once the ATN
directory has been commissioned and set in operation for AMHS, it can be readily extended
and used
for further, non-AMHS/AFTN applications.
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