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| == IPv6 deployment == | == IPv6 deployment == | ||
| Disadvantages | |||
| - to be reachable from the IPv4 universe during the transition phase, you still need an IPv4-address or some kind of ] (=shared IP-adress) in the gateway routers (IPv6<-->IPv4) which adds complexity there and means the large address space promised by the specification effectively can't be used immediately. | |||
| To do: | To do: | ||
Revision as of 14:13, 5 February 2004
IPv6 is version 6 of the Internet Protocol. IPv6 is intended to replace the previous standard, IPv4, which only supports up to about 4 billion (4 × 10) addresses, whereas IPv6 supports up to about 3.4 × 10 addresses.
IPv6 is the second version of the Internet Protocol to be widely deployed, and is expected (as of 2001) to form the basis for future expansion of the internet. In 2003, Nihon Keizai Shimbun (as cited in CNET Asia Staff, 2003) reported that Japan, China, and South Korea claimed to have made themselves determined to become the leading nations in internet technology, which would partially take the form of jointly developing IPv6, and completely adopting IPv6 starting in 2005.
The compelling reason behind the formation of IPv6 was lack of address space, especially in the heavily populated countries of Asia such as India and China.
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 2 ≈ 3.4 x 10. The number of IPv6 addresses can also be thought of as 16 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.
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 .
IPv6 deployment
Disadvantages
- to be reachable from the IPv4 universe during the transition phase, you still need an IPv4-address or some kind of NAT (=shared IP-adress) in the gateway routers (IPv6<-->IPv4) which adds complexity there and means the large address space promised by the specification effectively can't be used immediately.
To do:
Related IETF working groups
- 6bone IPv6 Backbone
- ipng IP Next Generation (concluded)
- ipv6 IP Version 6
- ipv6mib IPv6 MIB (concluded)
- multi6 Site Multihoming in IPv6
- v6ops IPv6 Operations