SITA's Voice Exchange and .aero

The imminent introduction of the SITA Voice Exchange will add a further incentive to customers to move towards convergence of voice and data. The technology at last brings together the strengths of IP VPN, the public switched telephone network (PSTN) and the Internet – and it originated in the early development work of the .aero team.

The benefits of convergence are increasingly well understood. At its heart is the fact that – before the introduction of IP telephony – operations, maintenance and customer premises equipment (CPE) was highly distributed and heterogeneous. After the adoption of IP telephony, operations are centralized, while maintenance and CPE are the same as for IP.

An increasing proportion of the air transport community appreciate the benefits. Convergence programmes have been successfully implemented in the US, South America, Europe, Australia, South Africa and India.

The facts are clear: IP is the way to go, via IP VPN and DSL systems. Voice services are increasingly becoming VoIP with PSTN numbering. But convergence will only be complete once the PSTN and Internet are working together transparently.

SITA's Voice Exchange introduces that process by aggregating travel and transport community data, voice (and, in the future, video) traffic for carriage via IP. Crucially, and for the first time, this includes integrating PSTN numbering into a voice community framework. The key feature of the project is that participating members will be able to dial their counterparts seamlessly. The call will be automatically routed to the preferred destination of the dialled participant, whether this is VoIP or PSTN.  Airline and airport staff will have one device to call from to make any type of call. Airlines and airports will also be able to configure how they wish to be reached, perhaps even requesting that their recorded voice mails are delivered to their e-mail box.

What has .aero to do with this?

The service is made possible by maximizing the processes and conventions available through the community-owned .aero domain. The key enabling elements are provided by the DNS (Domain Name System, or Service) and ENUM (Electronic NUMbering).

DNS is the crucial distributed database that underpins the Internet by mapping structured names to 'things'. It has almost infinite scalability. A wide variety of information can be distributed using various records defined in DNS. The records may contain host IP addresses or e-mail server addresses – as well as VoIP addresses, phone numbers, fax numbers, individual e-mail addresses, URIs (universal resource identifier) which identify available services, or even public cryptography keys. ENUM is a means of mapping phone numbers to Internet addresses, in the same way that domain names are mapped via the DNS.

The technology is complex, but just as complex is the way the technological and regulatory intersection of the Internet and the Public Sector Telephone Network (PSTN) is handled – including whether telephone numbers (of which there are already billions in place and which are language neutral) or Internet style addresses (using existing styles of Uniform Resource Indicators, or URIs) will be the optimum medium.

Initiated by .aero in 2004

The use of DNS and ENUM was first described in a five page technical concept paper prepared by the .aero team in late 2004. Since then, the concept has been fully embraced by SITA and turned into a major community project in its own right. The entire numbering scheme (ENUM) is being built in a domain name operated within the .aero naming structure &ndash

One forward-looking element of the project is the introduction of a dialling plan based on functions typically used in the air transport community. For example, users or a user application could dial a supervisor on the current baggage management shift of a given airline at a given airport, simply by dialling the mnemonic codes that could easily associated with this function, such as

It may be that the dialling process could be even more user friendly, accomplished by the application itself, leaving users time to focus on customers. In either case, the key advantage remains – the airline can itself configure HOW it wishes to be reached. The configuration, as well as any changes to it, are automatically propagated through the DNS system without a caller having to maintain an ever-changing phone number directory. This will foster a dramatic improvement in customer service AND deliver additional flexibility – simply because the destination user does not have to worry that a change of one phone number will require synchronization with multiple parties and carry high transition cost.


To be successful, such a dialling plan has to be open to any user from the community using any service provider. That independence is provided through its location within .aero and maintained as a policy development effort within .aero.


"The next decade will see the Net spread even further and start to become the basic communications infrastructure for almost anything … the Net will stop being a part of the telephone network. Instead the telephone network will become a part of the Net."

Vint Cerf, the man who wrote the original TCP/IP, in an interview with the BBC.