Submarine cables (enlarge)



The internet depends heavily on underwater cables, which carry information across the world's oceans. This map shows 93 of the world's major submarine cable systems, as well as 28 planned systems that are due to enter service by 2011.



The cables are vulnerable to damage from earthquakes and underwater landslides.



This was demonstrated in 2008, when the cables running through the Mediterranean were repeatedly disrupted, leaving thousands of people without internet access (see Why the Mediterranean is the Achilles heel of the web).



(Image: TeleGeography)

Submarine carrying capacity (enlarge)



In 1956, North America was connected to Europe by an undersea cable called TAT-1. It was the world's first submarine telephone system, although telegraph cables had crossed for the ocean for a century.



Trans-Atlantic cable capacity soared over the next 50 years, reaching nearly 10 Tbps in 2008.



In recent years, the annual growth of trans-Atlantic capacity has slowed, while the growth rates on the intra-Asian and Europe-Asia routes have increased rapidly.



Countries are colour-coded according to the amount of capacity deployed by carriers, ISPs, and enterprises to carry traffic across international borders (see "estimated international bandwidth usage by country", bottom left)



(Image: TeleGeography)

Internet census 2008 (enlarge)



The team has since brought the census up to date for 2008.



(Image: John Heidemann, University of Southern California)

Internet traffic in 2002 (enlarge)



Internet traffic is growing by about 50% annually, with video and music streaming rising fastest.



At the same time, the web is becoming divided along language lines.



(Data sources: InternetWorldStats.com, TeleGeography Research, IDC, The Radicati Group)

Internet traffic in 2004 (enlarge)



While traffic grew between 2002 and 2004 in all the countries shown here, the most dramatic changes were in India and China.



Both countries roughly doubled their population with access to the internet.



(Data sources: InternetWorldStats.com, TeleGeography Research, IDC, The Radicati Group)