umber of subscribers, inter-arrival of calls is also well modelled. In contrast, the required time for transmit- ting a data file is variable and depends on the size of the file, as well as the capability of the telecommunications equipment. The traffic character is also different to that of voice: computer data are generated in bursts and have a short active length followed by long inactive periods. As a result of these, using the same circuit-switched tech- nologies of voice communications which assigns a fixed bandwidth was inefficient because (a) the bandwidth could be excessive and (b) it could only be used for a very short period of activity and left idle for long periods. Furthermore, as computer communications are relatively delay insensi- tive, a store and forward system works well with data as real-time communications is not necessary. A queuing system which considered waiting time as well as different transmission speeds could work well for data transmission. Such a theoretical framework for computer data traffic and associated performance metric formulas was published by Leonard Kleinrock (pictured), 2 whilst a PhD student at MIT, in 1962 [2]. Computer communications also benefited from a US military project. Around the same time as Kleinrock's research was published, a project was funded by the United Computer room: NASA Ames Research Center (NASA-ARC) (NIX A-28284) https://commons.wikimedia.org/ wiki/File%3AIBM_7090_computer.jpg. Punch card: Blue-punch-card-front.png: Gwern derivative work: agr (Blue- punch-card-front.png) https://commons.wikimedia.org/wiki/File%3ABlue-punch-card-front-horiz.png. Magnetic tape: Hannes Grobe 23:27, 16 December 2006 (UTC) (own work). Used under CC BY-SA 2.5 (https://commons. wikimedia.org/wiki/File%3AMagnetic-tape_hg.jpg) Packetised Data Communications States military to develop a data communication system that could withstand a nuclear attack by the then Soviet Union. It was feared that such an attack would destroy telecommunications hubs and cut off command and cont