Recent DRI Projects

Irish Aviation Authority Air-Ground Communication System

The Air Ground communication system, installed by DRI in early 1998, is a totally distributed system connected on a dual 10BaseT local-area-network (LAN) that provides for communication between aircraft on the north Atlantic and air traffic controllers in Scotland. The north Atlantic is the most heavily traveled international route and the new system totally eliminated the increasing message delays, even during the peak hours of the peak period from June through September.

Since the system employs 16 PCs to cover the different radio frequencies, and the PCs are interchangeable, there is no longer any possibility of system failure. The dual-LAN and multiple gateways eliminate any ‘single-point-of-failure’. Corrective maintenance takes only 10 minutes and consists of simply replacing the entire PC. Because of the large quantity of on-line low-cost redundant positions available, any corrective maintenance can be deferred until day-shift staff is available.

All user interface functionality is totally automated, even to the point where position reports are geographically addressed, based on the current and estimated position of the flight. Quality control is greatly enhanced since all position reports are validated based on ‘reasonableness checking’ parameters of flight level, speed, time, latitude, longitude, and aircraft type. For example, the ‘reasonableness checking’ parameters for a Concorde flight position report are different than those for an ordinary commercial aircraft.

FAA NADIN-IA System Enhancement

DRI recently replaced all of the advanced peripheral systems, previously developed by DRI, with newer higher capacity systems that are based on industry standard SCSI interface. These new subsystems are non-proprietary peripherals and can extend the life cycle of the NADIN-IA system by at least 5 years. DRI also provides on-going technical support on an annual contract basis for this FAA AFTN system.

Irish Aviation Authority AFTN Communication System

The AFTN MMS system, developed by DRI, was the first system implemented on the IAA national wide-area-network. As part of this project, DRI was tasked with selecting the routers to be used throughout the entire national network. The DRI AFTN system is now integrated with radar and other navigational aids on this common national WAN. Because the MMS system extends the redundancy and error correction beyond the boundary of the WAN, the AFTN system is more reliable than the other systems operating on the same WAN.

The routing and switching functions are distributed across 5 PCs, any one of which is capable of handling the entire traffic load. Since there is no fixed relationship between a switch PC port and the distant concentrator port, any PC can and does address any other PC in the entire network. This feature makes a system crash impossible. The low cost PCs also make feasible the redundancy at all points throughout the network. This same low cost PC based remote intelligence makes available the error correcting Ack/Nak protocol at even the most remote AFTN terminal in the system. This MMS Ack/Nak protocol operates at the level above the Ack/Nak protocol built into the protocol of routers transporting the AFTN message at the lowest level.

Eventually, when the ATN is finally deployed, it can be easily integrated with the current MMS AFTN system, by simply making entries in the routing tables of the routers. The routers will handle the protocol translation (if any), and the MMS system will handle the ICAO address translation. DRI also offers, as an option, X.400 message capability and the AMHS gateway B functionality. Thus, if necessary, the existing MMS system can be incrementally converted into a full AMHS system required by the ATN specification, without any change to the existing hardware components.

This MMS system is the first AFTN system to provide two-way AFTN dial-up access to and from the regional airports and other authorized users. The dial-up access service implements extensive protection against denial-of-service attacks without depending upon expensive routers and remote access servers. The entire dial-up service uses only industry standard V.90 modems at the switching centers, concentrators and remote user sites. The software is optimized to minimize toll charges, call blocking, and call congestion to the extent that relatively few telephone lines can service a substantial number of remote users. For any user transferring less than 700 messages per day, the dial-up service is more economical than a dedicated leased line. This same dial-up service can also be implemented to provide dial backup service for any of the concentrators. However, due to the already extensive redundancy of the Cisco routers and the 'partial mesh' network, this additional backup is not required.

In addition to the main switching system and concentrators, a totally independent ‘contingency switch’ is operating in parallel with the main switch. This ‘contingency switch’ is located 18 miles away from the main switch. Its sole purpose is to take over the network in the event of a physical catastrophic event, such as fire, flood, or explosion, at the main switching system. Since this unmanned ‘contingency switch’ operates on the same WAN as the main switching system, it receives the same input traffic, directly from the concentrators, at the same time as the main switching system. The ‘contingency switch’ and the main switching center can both be controlled from a remote location.

This IAA AFTN system provides almost unlimited scalability. Even with no expansion however, the current IAA system could easily handle the most heavily loaded AFTN systems currently in operation, such as the FAA NADIN-IA system in Atlanta and Salt Lake City. Of even greater importance than scalability is the fact that this MMS system provides the IAA with total vendor independence and guaranteed long-term low cost maintainability. The IAA MMS system is the most advanced AFTN system now in operation.

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