Digging up the past of networks and the birth of Ethernet

Following on from the launching of Zilog's Z-Net local area network, it seems an appropriate time to take a look at a principal competitor, Ethernet, particularly as the three companies participating in this scheme – Intel, Digital Equipment Corporation and Xerox – held a European seminar on the subject in Amsterdam on 2nd March.

Why do we need local area networks? To answer this it is necessary to recap briefly on the history of data processing. In the 'forties and 'fifties, mainframe computers (macros) operated on the batch processing principle, with users queuing to run their jobs. Their programs frequently crashed, had to be debugged and then re-submitted, resulting in taking up a spot at the back of the queue again.

When transistor technology came along mainframes began to shrink in size and also in price: this allowed Digital Equipment (DEC) in 1963 to introduce the first commercial timesharing system, the PDP6. This overcame the queue problem to some extent by allowing up to 16 users to have simultaneous access to the machine. Development continued throughout the 'sixties during which the PDP8 minicomputer came along and achieved a dominant-.position as an industrial workhorse. A breakthrough came in 1972 when timesharing was made available on minis. This was an important event, since it brought computers out of machine rooms and into user offices. The next step was to link minis and terminals to macros, which resulted in the well-known 'spaghetti' problems associated with vast quantities of hard wiring.

In the mid-seventies, with the advent of personal computers, interconnection between micros, minis and macros had become a pressing problem. Many of these small machines could not access data on larger machines, or other small machines at different locations. This problem led to the conception of the single cable local area network (LAN). Dropping a cable down a lift shaft with a branch on each floor could link hundreds of different machines from various manufacturers into an intelligent communications network; more importantly, it would provide the necessary structure to manage distributed computing.

Xerox Corporation began working on the idea in 1975 and developed the basic local network design. Agreement was reached with Intel to develop the VLSI components and with DEC to supply system expertise in transceivers and minicomputer networks. Between them and, in the case of Xerox, $10 million later, specifications were available and protocol laied down to encourage widespread implementation.

Many big companies, like ICL, Olivetti, Hewlett-Packard and Nix-dorf, are committed to designing future products for use on the Ethernet network. At the present time there have been over 270 applications from interested firms, of which number 22 have announced agreement on compatibility. Furthermore considerable interest has been generated in the process control industry and several firms have entered into negotiations with Xerox to establish the feasibility of introducing Ethernet protocol into instrumentation projects.

Ethernet has been field-proven for over five years at various Xerox sites throughout the USA. It has over 7000 man-years of development behind it, sufficient to dispel many of the myths surrounding it. Criticisms which have been leveled at the Ethernet concept concentrate on performance, cost and the limited number of attachments possible. The first of these has been largely answered by Xerox's William Lynch, Answering the question: 'Can I guarantee that my message will get there in a tenth of a second if I use Ethernet?' He says: 'Yes! Data can get from sender to receiver in a tenth or a hundredth of a second almost always. Conservatively, it can get there in a hundredth of a second upwards of 90% of the time.

DEC put it another way: the entire contents of Tolstoy's War and Peace could be transmitted in 4.4s' concerning the number of attachments that can be 'hung' on the network. Ethernet has 1024 tap locations each of which can interface several terminals. Servicing 2000 is not seen as a problem the idea that Ethernet is just a development project which would never be implemented has been well and truly scotched. Already there are over 40 installations up and running in the USA. So far as the UK is concerned, the Greater London Council's installation is due to come on-line this month.

Text C

New words and word combinations:

1) a computer game – компьютерная игра; 2) to save – сохранить, сэкономить; 3) counterpart – партнёр; 4) tools – инструменты; 5) to require – требовать; 6) equipment – оборудование; 7) соnsumer – потребитель;           8) to correlate – находиться в каком-либо соотношении; 9) а survey – обозрение, осмотр; 10) а device – устройство; 11) а pattern – образец, модель; 12) to face smth. – оказаться лицом к …; 13) to embark – грузить; 14) software – nporpaммнoe обеспечение; 15) hardware – системный блок.