By Greg Smith, Service Provider Marketing Manager, Cisco
Today we take instant communications for granted and our latest Cisco Visual Networking Index predicts that we’ll soon reach the “Zettabyte Era” for global IP traffic (a zettabyte being 10^21 bytes). Recently I had an opportunity to see a bit of telecommunications history from what I’ll call the “Kilobyte Era”. While visiting a family I knew in Saverne, a small town outside of Strasbourg, France we toured a local castle (Castle Haut-Barr) with a view of the countryside. Besides the 12th century castle there was a (restored) tower from the original Paris-Strasbourg optical semaphore system, one of the first communications networks in the world. I’d read about this system but never actually seen it and my hosts were gracious enough to let me “geek out” on this bit of networking history.
Deployment of the network started in 1792 by French engineer Claude Chappe and used a series of towers stretching between several frontier cities and the capital of Paris. By using a set of mechanical arms in various positions that could be seen by using a telescope in the next tower (typical distance was about 10 km) and replicated a message could be quickly transmitted. The mechanical arms could form up to 92 symbols that mapped into a code book of over 8000 words and phrases to deliver the final message.The speed of the line varied with the weather, but the line between Paris and Lille (approximately 230 km) could send a complete message of 36 symbols in about 32 minutes. Of course this system could only work during the day and in good weather. Rain, fog or darkness would shut down the network. Contrast this rate of just over one symbol per minute with Cisco’s latest DWDM optical technology demonstration showing one trillion bits per second (and of course, independent of the weather!).
France was ultimately covered with a network of 556 stations stretching a total distance of 4,800 kilometers. It was used for military and national communications until the 1850s when the electrical telegraph became widely available. One can also argue that Chappe even helped invent “Class of Service” since among his symbols were included “petite urgence” and “grande urgence” so that prioritized messages could be sent first.
For more information on the Chappe Network see this link (French only) at Ecole Centrale Lyon or the Historical Society for the Mail and France Telecom in Alsace (French, English, and German, click on the “Tour Chappe” link).
Photo credit Daniel Sandner