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The period 1983 - 1986
Data communication: the FEL-LAN and wargames on the move

Wargames on the move

The Operations Research division went on the move several times to demonstrate Wargame and other models at our customer premises. This required long-haul networks. One of the exercises required a link between several military transmitter stations at the Veluwe (a part of the Netherlands) and the system CYBER 74 using several public and military microwave transmission links.
The main problem was the generator that provided power to the communication modules mounted on a military vehicle. The AC power frequency slowly decreased from 50 Hz to 45 Hz. At 45 Hz, the characters typed on a terminal arrived too slow at the CYBER system causing wrong characters to be recognised. Every twenty minutes slowly adjusting the frequency by hand was the remedy.

During another exercise, a number of terminals on the airbase Twente were connected up the Laboratory. At the inner court of the Laboratory, a military communications vehicle of the Royal Netherlands Army was parked, and its microwave antenna-mast was unfold. Through a window, twelve terminal lines connected the transmission system on one hand and the CYBER on the other hand. In the week of trials before the exercise, communications using over 12 hops through the Netherlands worked only a couple of minutes before the links broke off due to unknown causes. The solution was found by a Lieutenant-Colonel. In case the link did not work flawlessly before Friday 13.00 hours, he personally would revoke the weekend leave passes of all involved soldiers. As by magic, within an hour the total communication link was stable and without dropped connections.

To reduce the reliance upon weak communication links, the Wargame group bought a Digital MicroVAX. Just one day before another exercise, at the airbase Twente, struck in a disaster. Information at the disk in the system slowly degraded and became unreliable. When moving the MicroVAX temporarily to an adjacent room were people could work a little more quiet sorting out the problem, the problems magically disappeared. When going back to the full set-up with all the terminals active, the problem re-appeared again. At the Laboratory, the phone rang: "Did we have an idea?" "In what kind of room are you? Do you have a reliable power source? Is it too hot in that room?" No disturbances like that. "When looking out of the window, we see the tarmac and take-offs and landings; a nice view. By the way, we see a radar nearby, that's ok isn't it?" Thinking of our long history of radars influencing our computer equipment we suggested to turn the system and apply some shielding. Yes, the problems became seemed to disappear. They then took measures of the system size and phoned those details to our mechanical department. Some meters of chicken wire was bought and within a couple of hours, a cage of Faraday was put together with the MicroVax and moved to Twente.

Apart from the wargames, the Operations Research-division presented several courses twice a year at the Hogere Krijgsschool (HKS). The Soltau-courses had a practical computer component, the CYBER was used for. It was always a burden to free enough terminals for that event.

Increasing computer requirements: the Local Area Network

The DATUS-port selector configuration was expanded many times, but the exploding demand for terminal lines could not be satisfied. As users many times found all ports to the CYBER being occupied, a second 2551 with eight CLA's (32 asynchronous lines) had to be installed.

VAX 11/750 CPU and 2551

In 1985/86, the IT-policy committee started a project team that had to investigate how the FEL could install a Local Area Network. This included the investigation of security aspects. A student of the Technical University Delft gave support to that work. He had to look at the security aspects both from a theoretical and praktical view.
The practical aspects included a "mini"-network based on the DECnet architecture. This network comprised the three VAX 11/750's (VA, VC en VG), a PDP 11/34, a PDP 11/44 and a PDP 11/725. As a good researcher, the student was able to run programs on the VAX for administrative purposes (VA) without having any authorisation to use that system.

On the DECnet-network, a throughput of 150 MB/hour was meassured on the VAX 11/750.

After a thorough study, the workgroup asked several potential vendors for a network design and price. LANs at that time, especially when the LAN had to be designed for use with equipment of multiple vendors, were a "terra nova" in The Netherlands. Well-known computer companies, foresaw "grounding problems" and excluded those from guarantee. Obviously, they did not understand the IEEE 802.3 network standard that was asked for the Laboratory. Otherwise, they would have understand that these problems cannot exist in case the network design was done properly. At the end, the committee advised for the installation of the network by Control Data which had a proposal that included subcontractors for the installation itself under responsibility of Control Data Netherlands Inc. The FEL local area network, the FELLAN, was installed as a star-like network around the central data communication room. It consisted of ten thick Ethernet segments of 500 meter each.

The LAN-tranceivers were delivered by another company. The FEL was the only organisation that only accepted the tranceivers, when they passed the IEEE 802.3 specification tests. Even marginal differences of the specifications were not accepted, despite the fact that those tranceivers worked in other networks flawlessly.

The DECnet used a pre- IEEE 802.3 standard based on the (Xerox) XNS-header specifications. In principle, the DECnet data layer specifications were in conflict with the IEEE 802.3 international standard. In practice, however, the length field did not conflict. Thus, both the IEEE 802.3 specification confirming systems and DECnet based systems could use the same Local Area Network (LAN), although the network managers had to take care of the right setting of the tranceivers (with/without "heart beat").



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