IPv6

1.WHAT’S IPV6?

IPv6 is short for "Internet Protocol Version 6". IPv6 is the "next generation" protocol designed by the IETF to replace the current version Internet Protocol, IP Version 4 ("IPv4"). 

Most of today's Internet uses IPv4, which is now nearly twenty years old. IPv4 has been remarkably resilient in spite of its age, but it is beginning to have problems. Most importantly, there is a growing shortage of IPv4 addresses, which are needed by all new machines added to the Internet. 

IPv6 fixes a number of problems in IPv4, such as the limited number of available IPv4 addresses. It also adds many improvements to IPv4 in areas such as routing and network auto configuration. IPv6 is expected to gradually replace IPv4, with the two coexisting for a number of years during a transition period. 

Some introductory information about the protocol can be found in our IPv6 FAQ. For those interested in the technical details, we have a list of IPv6 related specifications.

2. IPV6 ADDRESSING :

The most dramatic change from IPv4 to IPv6 is the length of network addresses. IPv6 addresses, as defined by RFC 2373 and RFC 2374, are 128 bits long; this corresponds to 32 hexadecimal digits, which are normally used when writing IPv6 addresses, as described in the following section.

The number of possible addresses in IPv6 is 2¹²⁸ ≈ 3.4 x 10³⁸. The number of IPv6 addresses can also be thought of as 16³² as each of the 32 hexadecimal digits can take 16 values (see combinatorics).

In some situations, IPv6 addresses are composed of two logical parts: a 64-bit network prefix, and a 64-bit host-addressing part, which is often automatically generated from the interface MAC address. 

3. NOTATION FOR IPV6 ADDRESSES:

IPv6 addresses are 128 bits long but are normally written as eight groups of 4 hexadecimal digits each. For example,

 3ffe:6a88:85a3:08d3:1319:8a2e:0370:7344

is a valid IPv6 address.

If a 4 digit group is 0000, it may be omitted. For example,

 3ffe:6a88:85a3:0000:1319:8a2e:0370:7344 

is the same IPv6 address as

 3ffe:6a88:85a3::1319:8a2e:0370:7344

Following this rule, if more than two consecutive colons result from this omission, they may be reduced to two colons, as long as there is only one group of more than two consecutive colons. Thus

 2001:2353:0000:0000:0000:0000:1428:57ab

 2001:2353:0000:0000:0000::1428:57ab

 2001:2353:0:0:0:0:1428:57ab

 2001:2353:0::0:1428:57ab

 2001:2353::1428:57ab 

are all valid and mean the same thing, but

 2001::25de::cade

is invalid.

Also leading zeros in all groups can be omitted, thus

 2001:2353:02de::0e13

is the same thing as

 2001:2353:2de::e13

If the address is an IPv4 address in disguise, the last 32 bits may be written in decimal; thus

 ::ffff:192.168.89.9 is the same as

 ::ffff:c0a8:5909, but not the same as

 ::192.168.89.9 or

 ::c0a8:5909.

The ::ffff:1.2.3.4 format is called an IPv4-mapped address, and is deprecated. The ::1.2.3.4 format is an IPv4-compatible address.

IPv4 addresses are easily convertible to IPv6 format. For instance, if the IPv4 address was 135.75.43.52, it could be converted to

0000:0000:0000:0000:0000:0000:874B:2B34 or ::874B:2B34.

Then again, one could use the hybrid notation (IPv4 mapped addresses), in which case the address would be ::135.75.43.52 

4.IPV6 HEADER:

            The most important and the only working part of any protocol is its HEADER. Without a Header any Protocol is useless. And thus its description and explanation is mandatory. The figure shown below is the IPV6 Header, which is much more simplified than its previous one.

   Flow Label:                20-bit flow label.

IPV6 HEADER