Internet protocol suite
| Application layer |
HTTP, SMTP, FTP, SSH, IRC, SNMP ...
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| Transport layer |
TCP, UDP, SCTP, RTP, DCCP ...
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| Network layer |
IPv4, IPv6, ARP, IPX ...
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| Data link layer |
Ethernet, 802.11 WiFi, Token ring, FDDI, ...
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IPv6 is version 6 of the Internet Protocol; it was initially called IP Next Generation (IPng) when it was picked as the winner in the IETF's IPng selection process. IPv6 is intended to replace the previous standard, IPv4, which only supports up to about 4 billion (4 × 109) addresses, whereas IPv6 supports up to about 3.4 × 1038 (3.4 dodecillion) addresses. This is the equivalent of 4.3 × 1020 addresses per inch˛ (6.7 × 1017 addresses/mm˛) of the Earth's surface. It is expected that IPv4 will be supported until at least 2025, to allow time for bugs and system errors to be corrected.
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. See the article IPv4 address exhaustion for more on this topic. However since the introduction of NAT this is not such a big problem any more. Currently the big drive for IPv6 is new uses, such as mobility, quality of service, privacy extension and so on.
IPv6 is the second version of the Internet Protocol to be formally adopted for general use. (There was also an IPv5, but it was not a successor to IPv4; rather, it was an experimental flow-oriented streaming protocol, intended to support voice, video, and audio.)
The plan is for IPv6 to form the basis for future expansion of the Internet. Although IPv6 was adopted by the IETF as the successor to IPv4 over ten years ago (in 1994), worldwide IPv6 deployment as a publicly-accessible internet is still only a few percent [1] of the size of the worldwide IPv4 Internet [2].
1 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 combinatoricsCombinatorics Discrete mathematics Combinatorics is a branch of mathematics that studies finite collections of objects that satisfy specified criteria, and is in particular concerned with "counting" the objects in those collections enumerative combinatori).
In many 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 addressIn computer networking a media access control address (MAC address is a code on most forms of networking equipment that allows for that device to be uniquely identified. Address details A MAC address is an identifier physically stored inside a network car. The host part is called a EUI-64 (or 64-bit Extended Unique Identifier).
