More Internet traffic is expected to be carried via tunnels as the Internet infrastructure migrates from IPv4, the current version of the Internet protocol, to the long-anticipated upgrade known as IPv6.
IPv4 uses 32-bit addresses and can support 4.3 billion devices connected directly to the Internet. IPv6, on the other hand, uses 128-bit addresses and supports a virtually unlimited number of devices -- 2 to the 128th power.

The regional Internet registries said in April 2010 that less than 8% of IPv4 addresses remain unallocated. The remaining IPv4 addresses are expected to run out in 2011 or 2012.

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