Internet Protocol Version 6 (IPv6)

As the Internet community continues to grow, using IPv4 addresses, we are quickly running out of address space. IPv6, initially called IPng (IP Next Generation), improves Internet capability by using a simplified header format, support for authentication and privacy, autoconfiguration of address assignments, and new quality-of-service capabilities. Specifically, here are the enhancements IPv6 provides:

• Expanded addressing capabilities Because IPv4 is 32 bits, it has approximately a 4,300,000,000 address space in a decimal number. This amount is absolutely insufficient for the Internet worldwide because it is smaller than the population of the world. It is estimated that IPv4 addresses will be exhausted in about the year 2008 (give or take three years).

  IPv6 increases the IP address size from 32 bits to 128 bits to support more levels of addressing hierarchy. IPv6 supports addresses that are four times the number of bits as IPv4 addresses (128 vs. 32). Thus, the number of potential addresses is four billion × four billion × four billion the size of the IPv4 address space.

  Note

  IPv6 supports addresses that are four times the number of bits as IPv4 addresses (128 vs. 32). This is four billion × four billion × four billion times the size of the current IPv4 address space. This works out to be 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses.

  Theoretically, this is approximately 665,570,793,348,866,943,898,599 addresses per square meter of the surface of planet Earth (assuming the Earth’s surface is 511,263,971,197,990 square meters).

  
  

  Here’s an example of an IPv6 address:

  0000:0000:0000:0000:0000:FFFF:192.168.0.2

  The first 48 bits of the address represent the public topology. The next 16 bits represent the site topology.

• Improved routing When the number of organizations connected to the Internet increases, the memory and route information increases, too. It puts the burden on the router, which forwards the packet and results in decreased look-up speed. This could be a fatal problem for a router with little capacity. Improvements in IPv6 addressing expand routing over what was available in IPv4.

• Security The IPv6 basic specification includes security and privacy enhancements. The current Internet has a number of security problems. The Internet lacks effective privacy and effective authentication mechanisms below the application layer. IPv6 remedies these shortcomings by having two integrated options that provide security services:

  • Encapsulated security payload (provides packet encryption)

  • Authentication header (provides source authentication)

• Real-time traffic support A new capability has been added to enable the labeling of packets belonging to particular traffic flows for which the sender requests special handling. For example, the sender can request nondefault quality of service or real-time service.

  To support real-time traffic such as video conferencing, IPv6 has “flow label.” Using flow label, a router can know which end-to-end flow a packet belongs to and then can find out the packet that belongs to real-time traffic.

  In addition, a 4-bit priority field in the IPv6 header enables a source to identify the desired delivery priority of its packets, relative to other packets from the same source.

• Header format simplification Some IPv4 header fields have been dropped or made optional. This change reduces the common-case processing cost of packet handling. This change also keeps the bandwidth cost of the IPv6 header as low as possible, despite the increased size of the addresses. Even though the IPv6 addresses are four times longer than the IPv4 addresses, the IPv6 header is only twice the size of the IPv4 header.

• Improved support for options Changes in the way IP header options are encoded allows for more efficient forwarding. Also, the length of options has less stringent limits. The changes also provide greater flexibility for introducing new options in the future.