The EUROCONTROL Surveillance Data Distribution System (SDDS) is a versatile, high-performance communications gateway that provides value-added services for the safe and secure distribution of ASTERIX (EUROCONTROL’s All purpose Structured suRveillance Information eXchange) format.

SDDS enables ANSPs to exchange surveillance data, in an efficient manner,  contributing to the reliable and efficient operation of the pan-European ATM network.

With the objective to protect ATC system from deficient data  from upstream systems that may harm it, SDDS:

  • checks surveillance data for syntactic and semantic errors (deep packet filtering);
  • provides firewall services;
  • is able to filter out data that may cause processing problems;

Main features

SDDS enhances safety, security and interoperability by providing the following features:


Safety-related features include a high availability hardware platform, alternative data path selection, syntax and range checking, static and dynamic filtering.


Security-related features begin with a top-level architecture that separates payload and management information, as well as separation between the inter-centre and intra-centre communications.


Gateway functions allow the simultaneous use of a wide variety of communication protocols. These gateway functions are not restricted to surveillance data. The SDDS can be used in 'transparent mode' for practically any type of information. An automatic switchover function ensures data availability in case of loss of a data source by activating the connection to a substitute.

ASTERIX data format conversion

ASTERIX data format conversion is an interoperability feature makes it possible for technologies (e.g. ADS-B, Multilateration) to be introduced, without having to update end systems at the same time.


The static filtering capabilities allow data streams to be tailored to user's needs by applying a wide range of filtering options (e.g. geographical filter, primary/secondary, specific SSR code ranges), while dynamic filtering helps prevent uncontrolled loss of data due to overload. The SDDS uses a lean publish/subscribe mechanism to manage the connections to the provided services, thereby facilitating interoperability and reduce configuration effort. This publish/subscribe mechanism also ensures that users can only access data for which they are authorised.

SDDS - PENS compatibility

One of the main SDDS requirements was that no further technology pre-requisites were permitted - with one exception: the fact that communication should be based on the Internet Protocol (IP).

SDDS - SWIM compatibility

When the SDDS team started the specification in 2008, SWIM was not on their radar; SDDS was not initially designed to be a SWIM-solution.

It soon became apparent, however, that a lot of 'lower level' functions of the SDDS were also present in other communication front-ends. So, it was decided to base the system on a layered and modular design and to use a generic platform for the operating system, the IP communication layers and the system monitoring, control and configuration facilities. Through well documented interfaces, additional (even non-surveillance) applications can be implemented as plug-ins. In the near future, the layered design of the SDDS will facilitate its transformation into a real SWIM solution; this will be done as soon as SWIM’s requirements are mature.

Efficient exchange of surveillance data

Surveillance products are constantly evolving: they have to demonstrate innovation and adaptability while meeting the safety and quality requirements of operational systems. When we were first discussing replacing the suRveillance Message Conversion and Distribution Equipment (RMCDE), we asked ourselves whether a value-added network node was still necessary, while introducing an IP-based network infrastructure.

Starting point of a platform-based architecture

It is a general misconception that an IP network infrastructure can cover all communication needs. But, just like the Internet, specific systems that handle content are still needed. On the other hand, the common use of Internet Protocols makes for an open invitation to re-use components wherever possible. This is the starting point for a platform-based architecture.

With the platform-based architecture of the Surveillance Data Distribution System (SDDS), it is possible to re-use a significant portion of the implementation used for other types of message-based service networks (such as air-ground datalinks, meteorological data and even the AMHS - ATM Message Handling System). All that is needed is the development of a domain-specific plug-in. Essential characteristics are cost efficiency through platform- based development, compatibility with international programmes through the use of standard protocols and agreed technologies with a strong focus on security aspects.

SDDS applications

Inter-centre distribution

SDDS was primarily developed for inter-centre communications. In each of the centres in a "network", an SDDS - or similar system - collects local surveillance data (from sensors or surveillance data processing systems) and distributes it to neighbouring centres.

Intra-centre distribution

Another application is the distribution of surveillance data within a centre. The filter and conversion capability allows data streams to be tailored for different user groups (Area Control, Approach and Tower, but also data processing systems with different needs).

International gateway

A more generic application would be as a general-purpose international gateway. The SDDS allows different protocol types to be connected. Its advanced security features ensure that data crossing borders is subject to high levels of control.

Support and maintenance

Support and maintenance is managed by the EUROCONTROL SDDS Implementation and Operational Support Team (SIMOS). SIMOS provides direct support to the users, such as SDDS-related incident and problem management, training and the further evolution of the SDDS. In turn, the EUROCONTROL team is supported by an industrial partner which is specifically responsible for documentation and software maintenance and the implementation of new functions.