IP Version 6

The following notes come directly from Wikipedia:

IPv5 was not a successor to IPv4, but an experimental flow-oriented streaming protocol intended to support video and audio.

IPv6 addresses are normally written as eight groups of four hexadecimal digits. For example, 2001 : 0db8 : 85a3 : 08d3 : 1319 : 8a2e : 0370 : 7334 is a valid IPv6 address.

IPv4 mapped IPv6 addresses constitute a special class of IPv6 addresses. Such an IPv6 address has its first 80 bits set to zero, the next 16 set to one, while its last 32 bits represents an IPv4 address. For example, : : ffff : c000 : 280 is the mapped IPv6 address for 192.0.2.128.

It is common to see examples that attempt to show that the IPv6 address space is absurdly large. For example, IPv6 supports 2¹²⁸ (about 3.4×10³⁸) addresses, or approximately 5×10²⁸ addresses for each of the roughly 6.5 billion people alive today. In a different perspective, this is 252 addresses for every star in the known universe - a million times as many addresses per star than IPv4 supported for our single planet.

As of November 2007, IPv6 accounts for a minuscule percentage of the live addresses in the publicly-accessible Internet, which is still dominated by IPv4.

Estimates as to when the pool of available IPv4 addresses will be exhausted vary widely, and should be taken with caution. In 2003, Paul Wilson (director of APNIC) stated that, based on then-current rates of deployment, the available space would last until 2023. In September 2005 a report by Cisco Systems reported that the pool of available addresses would be exhausted in as little as 4 to 5 years. As of November 2007, a daily updated report projected that the IANA pool of unallocated addresses would be exhausted in May 2010, with the various Regional Internet Registries using up their allocations from IANA in April 2011. This report also argues that, if assigned but unused addresses were reclaimed and used to meet continuing demand, allocation of IPv4 addresses could continue until 2017.

Government incentives

A number of governments, however, are starting to require support for IPv6 in new equipment. The U.S. Government, for example, has specified that the network backbones of all federal agencies must be capable of deploying IPv6 by 2008, and spent the money to acquire a /16 block 281 trillion network addresses to start the deployment.
The Peoples Republic of China has a 5 year plan for deployment of IPv6 called the China Next Generation Internet.

It is expected that IPv4 will be supported alongside IPv6 for the foreseeable future. IPv4-only nodes (clients or servers) will not be able to communicate directly with IPv6 nodes, and will need to go through an intermediary.

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