Submarine communication
By Charles Miller

In her World War One history book The Zimmerman Telegram, author Barbara Tuchman recounts the very first act of war by the British. On the day the Germans declared war, the Royal Navy sent out a ship to find all the trans-Atlantic communication cables connecting Germany. They snipped them in two and pulled up enough cable to make sure nobody could splice them back together again.

That act severely crippled Germany’s communications infrastructure. Telegrams and diplomatic communications that had taken hours then required weeks to be delivered through circuitous routes. Germans had to make use of the radio to send coded messages, and when they did, British intelligence listened in and broke the codes.

Some stories in the news in recent weeks remind me of this, and the fact that the world today is even more dependent on submarine communications cables as we were then.

A lot of Internet users mistakenly believe their connection takes place using satellite communications. Satellites in geostationary orbit 35,786 km above the equator are too far away and cause delays of about 230 milliseconds in handling traffic. The time it takes a signal to go up to a satellite and back down again is okay for some data, but just too long for most.

Most Internet traffic is carried over millions of miles of fiber-optic cable. Since the surface of the earth is two-thirds water, a lot of that fiber is under the oceans. These undersea fiber-optic cables handle more than 75 percent of the Internet and telephone traffic between the Mideast, Europe and the United States, and 90 percent of transmissions between Europe, the Middle East and Asia.

Look at a map of the world’s major underwater cables and it is easy to see they closely follow the major ocean shipping lanes. The ships sailing these waters carry things called anchors, and guess what happens when one of those anchors gets tangled up with a fiber-optic cable. Underwater seismic activity can also sever cables.

The system of cables is robust and has a great deal of redundancy in its design. When outages occur, the system can automatically reroute traffic around problem areas. At least up to a point, traffic can be rerouted through other cables and other countries… so long as other cables are still working. The extra load will likely cause a domino effect, resulting in Internet slowdowns or dropped connections around the world.

For example, let us say someone in London was exchanging emails with a friend in New York over the most direct cable under the North Atlantic. If that cable was lost, the mail could still find its way through the network taking a different route, say, London to Cairo to Sydney to Los Angeles and finally New York. Taking the long way around the world might delay it a few thousandths of a second, and it also puts more traffic load on top of the communications those other cables were already handling.

Breaks in these submarine cables are common; normally dozens per year just in the Atlantic. The companies responsible for maintaining them have special ships ready to sail when a repair job is needed, but that can take days.

What concerns some experts today is our reliance on these cables, and the likelihood that several of them could be damaged at the same time, resulting in major worldwide disruption of Internet traffic.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 044-415-101-8528 or email FAQ8 (at) SMAguru.com.