Size really does matter

16th October 1998 at 01:00
Getting sick of the World Wide Wait? Our nationalnetworks should eventually get the increased capacity we need, writes Nigel Paine

Ever wondered why it can take so long to log on to your favourite website? There is a one-word answer: bandwidth. The less bandwidth, the slower the connection is. This is why the issue is vital to the success of the Internet as a learning tool.

But as the discussion about the implementation of the National Grid for Learning begins in earnest, we seem to have forgotten the notion of a superhighway for education with large capacity networks. Instead, our focus has switched to the idea that any connection is a good connection.

Bandwidth can be likened to the water supply system. A server, then, is the reservoir. From it come massive pipes capable of carrying thousands of gallons. They split off into smaller pipes, capable of carrying hundreds of gallons.

These lead into local systems, capable of carrying tens of gallons, until finally we get to the narrow pipe in your house that can deliver a few gallons of water at a time. Plenty for you, but it certainly would not do for the whole street. The volume of water is essentially what is meant by bandwidth. Bandwidth equals the diameter of the pipe: bigger pipe means more bandwidth.

If you plumb your house with a tiny bore pipe that can only deliver drips of water, showering would not be very pleasant. Conversely, put a hose on the front of your tap and you will destroy everything in the kitchen while trying to get a glass of water. It is all about balance: getting supply versus demand right.

The problem with bandwidth is that very fast delivery is very expensive and what most people have access to is perhaps more like a drip, drip water supply than a gushing tap. With supply to the street fairly constricted as well, the occasional water shortage occurs when everyone turns their taps on at the same time.

Bandwidth is expressed in bits (of information) per second, thousands of bits (kilobits) per second and millions of bits per second (megabits per second).

Dial-up connections using a modem can give you 56k (kilobits) per second speed, and ISDN 128k and permanent leased lines anything up to 164 megabits per second.

The problem is that every person making use of a particular connection takes up a bit of the capacity. So, for instance, if 164 people log on to a 164 megabit line, they will get about one megabit each. A whole class logging on to a 128k ISDN line will give far less speed to each user than an individual logging on to a much slower dial-up connection. It is all logical - there is only so much water in the pipe.

This means that a dial-up Internet connection using a 56k modem will be suitable for just one or two simultaneous users. Although you might have a 56k modem, it will not always give you 56k per second of bandwidth. Speed depends on a number of factors, including:

* how many people are connected to the server at the same time; * how many are using your own local connection; * how crowded the main routes are from your internet service provider to the server you are accessing; * how quickly your computer can process the information it is receiving, and how quickly the server can process requests for information.

It stands to reason that it is a bad time to go online when everyone else is also trying to log on, such as early evenings and at weekends. This is when the whole Internet almost grinds to a halt and then lurches forward at snail's pace.

However, even 30 users trying to access one site at the same time can play havoc with response times. If you set pupils Internet-based tasks, do not send them all to the same page at the same time. Popular sites, such as the United States', are always going to be busy, so be patient - you will be in a queue. However, you should complain to your service provider if the bandwidth you have bought is rarely available.

You can check speeds by watching the download times in the bottom left hand corner of your browser window. Remember that to go from kilobits to kilobytes, you need to multiply by eight.

There are now increasing numbers of ways to make your connection: phone line and ISDN from telephone companies, cable modem or dial-up access from your cable provider, radio connections, and even low earth orbit satellite in the next few years. Eventually, like electricity and water, we generally will get the exact amount we need and bandwidth will cease to be an issue.

But in the meantime, acceptable bandwidth for schools remains a contentious issue. The matter of minimum entitlements must not be forgotten or rural schools will lose out to urban schools. We now know what sort of Internet access we get for our money and it is time to complain if it is not yet a viable classroom option. Government officials responsible for the National Grid for Learning need to work with telecommunication and cable companies to make sure that the increasing demand for bandwidth is catered for by a significant boost to Britain's national networks.

The much-vaunted Grid will only work when all of its various components operate in harmony. Adequate bandwidth is, most certainly, a vital element.

Nigel Paine is chief executive of the Scottish Council for Educational Technology

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