Internet Protocol Version 6

Address space limitation is the main motivation of the new Internet protocol specification. The global Internet has experienced many years of sustained exponential growth, doubling in size every nine months or faster. In 1999, on the average, a new host appeared on the Internet every two seconds (Comer 2000). However, the 32-bit address space of IPv4 is limited and, even more, unfair-divided between different organizations. While network address translation (NAT) technology seems to be a solution for some topologies, like managing multiple LANs of one corporation, it cannot handle the needs of new evolving Internet areas like for example China.

The most important changes specified with IPv6 are:

  1. Larger Addresses: The 128 Bits Addresses are the most noticeable change. The address space is greater than 3.4x10^38 which results in over 10^24 addresses per square meter of the earth's surface.
  2. New Datagram Format: Opposite to IPv4 the new protocol has a so-called Base Header of fixed length, namely a 40 Bytes Base Header. This Base Header may be followed by a so-called Extension Headers for special purposes. Whether an Extension Header follows or not is specified in the NEXT-HEADER field of the Base Header. Possible, already specified extension headers are for example headers with routing, fragmentation, authentication, and encryption information.
  3. Extension Capability: The concept of base and extension headers is a powerful instrument to adapt the protocol to future needs. In case, IPv6 needs to support a new feature, the only task is to specify a new extension header for it.
  4. Security: The protocols of IPsec for secure Internet communication are mandatory.
  5. End-to-End Fragmentation: IPv6 uses end-to-end fragmentation to avoid assembling and re-assembling overhead in routers. The sending host can either use the guaranteed minimum MTU of 1280 bytes or perform a Path MTU Discovery to determine the minimum MTU along the path to the destination host.

With the next generation Internet protocol IPv6 at the horizon, it is time to think about how applications can migrate to IPv6.