You decide to go online to check your e-mail and surf the web a little. You dial in to your ISP. Your modem dials and the connection is successful. When you download your e-mail from your local ISP everything is fine. But when you try to surf around, your computer just crawls along at a snail's pace. You have a brand new 56K modem connected to a good clean telephone line.

You remember your last call to your ISP's Help Desk and you check all the obvious things: your modem is plugged in, the light is flashing, and you have a TCP/IP address in your Network Control Panel. But your connection's speed is still slow.

So, you pick up the phone and call your ISP. Their Help Desk personnel are friendly, but they tell you that performance is slow for all customers and unfortunately there's nothing they can do about it. They tell you that the trouble is not with them, but with some part of the Internet. The problem been reported to some unnamed people out in the Internet somewhere, and all the ISP can do is ask you to patiently wait for the problem to be resolved.

You give up, leave your computer for a few hours, then dial in again later and everything is fine. What happened? What is it about the Internet that causes problems that are beyond the control of your ISP? The answer is that the Internet is like a food chain and one break can affect the whole system.

The Internet is a collection of many different networks, chained together at key junctions.

Your ISP accepts connections from your modem and their other customers, and all of these connections are first routed, or sent, through their own networks. Your local ISP has one or more high-speed connections from its own network out to the rest of the Internet. These connections go out to one or more "upstream'' ISPs, which are larger and connect many smaller ISPs to their own larger, faster networks.

The ISPs for Logic and North Rock connect to Carrier ISPs. Carrier ISPs may connect to more ISPs behind them, forming a hierarchy of ISPs that pass data ever onward towards its final destination.

But at some point these collections of ISPs eventually converge at a small number of very large, very fast central networks owned by companies called Carriers. Carrier networks connect to each other at several key junctions.

There are a small number of the carriers in the US, and Europe and other parts of the world, but none of these carriers forms the backbone of the Internet.

There is no one, central backbone to the Internet. All ISPs ultimately connect to one or more carriers, like Worldcom or AT&T.

Carrier networks form a collection of key junctions at which point other ISPs can exchange data. The key junctions between carrier networks are called Network Access Points (NAPs). NAPs are basically a collection of specialised devices called "switches'' and "routers'' that move data back and forth between the carriers at very high speeds. NAPs are basically the nerve centres of the Internet.

There were originally a total of only four NAPs in the United States: in New York, Washington DC, Chicago, and San Francisco.

This was back in the early 90s when the Internet maintained by the US government through the National Science Foundation. Since then, several more NAPs have been created, such as one built by Worldcom in San Jose, California called "MAE West'', and one built by ICS Network Systems in New York called "Big East''. But the number of NAPs is still relatively small.

It helps to visualise the Internet as a giant food chain. You, the user, are at the bottom of the food chain, sort of like an amoeba. Your ISP is the next level up in the food chain, sort of like a fly that ingests the amoeba. The upstream ISP that your local ISP connects to is like the frog that eats the fly.

And the network that this ISP connects to is the next level of the food chain, sort of like the weasel that eats the frog. If any one level of this food chain is disrupted, the whole food chain is affected. Just as a frog can starve if the population of flies drops dramatically, the Internet can suffer frustrating problems if any one of the ISP levels has a problem.

When you surf the web, your computer sends packets of data through your modem, up through these various levels of the Internet, through these central exchange points, and then down to the computer somewhere in the world that contains the specific web pages that you are trying to view.

The path that your packet takes is not always the most obvious path based on geography. You may dial in to a network in your neighbourhood, and you may be trying to connect to a web page that you know is located only a few miles away. But this web page may be connected to a different ISP, and that ISP may not have a direct connection to your ISP. Data from your computer may have to be passed up several layers of ISPs, often crossing hundreds of miles, before it reaches a network that has a connection back down to the ISP that connects to the computer with the web page you want to view. Don't be surprised if data going between Bermuda and Florida may get there via San Francisco. E-mail sent between a Logic customer and a North Rock customer has to go off the Island, out to the Internet, and then back on the Island again because these ISPs do not have a direct connection to each other.

The Internet: A food chain You can watch the path your traffic takes through the Internet by using the "traceroute'' command, which will list each network that your packet passes through on the way to its destination.

On a PC open a DOS prompt from the Start menu and type "tracert'' followed by the name of the computer you're trying to reach, such as "tracert www.cnn.com''. You will see a list of device-names that contain the names of the networks they are passing through.

You can type this same command several times in a row, and you may get a slightly different list each time, since data may take different routes through the Internet, depending on what routing decisions are made by each network along the path. Often, traffic may not go through a NAP at all, instead being exchanged between local companies that connect their networks together via private "peering arrangements'' within a specific geographic region.

Because there are so many networks that your data passes through, a problem at any of these points can cause problems to cascade through other parts of the Internet. Your local ISP may have alternate connections to different upstream ISPs, but if a problem appears at a common network somewhere upstream, it can affect all ISPs "below'' it. This is why you may find yourself calling your ISP to complain about slow performance and your ISP is unable to commit to a time that the problem will be resolved.

All they can do is contact their provider, and that provider may have to contact their provider, until the source of the problem is identified and resolved, causing all downstream ISPs to return to normal. On the Internet, like in the food chain, each level relies on the level above and below it to work correctly, and a balance between them must be maintained for it to all function smoothly.

When there are disruptions many ISP customers will suffer slow connections.

When this happens, shut off your computer, go outside, and give thanks that you have alternatives that the amoeba will never have.

*** Michelle Swartz's column appears on the first and third Wednesday of every month in The Royal Gazette's Personal Technology section. She can be reached at michelle y christers.net