IP address

From Wikipedia, the free encyclopedia

An IP address (Internet Protocol address) is a unique address that devices use in order to identify and communicate with each other on a computer network utilizing the Internet Protocol standard (IP). Any participating network device — including routers, computers, time-servers, printers, Internet fax machines, and some telephones — can have their own unique address.

An IP address can also be thought of as the equivalent of a street address or a phone number (compare: VoIP) for a computer or other network device on the Internet. Just as each street address and phone number uniquely identifies a building or telephone, an IP address can uniquely identify a specific computer or other network device on a network.

An IP address can appear to be shared by multiple client devices either because they are part of a shared hosting web server environment or because a proxy server (e.g. an ISP or anonymizer service) acts as an intermediary agent on behalf of its customers, in which case the real originating IP addresses might be hidden from the server receiving a request. The analogy to telephone systems would be the use of predial numbers (proxy) and extensions (shared).

IP addresses are managed and created by the Internet Assigned Numbers Authority. IANA generally assigns super-blocks to Regional Internet Registries, who in turn allocate smaller blocks to Internet Service Providers and enterprises.

1 IP versions
2 See also
3 External links
- 3.1 RFCs

[edit] IP versions

The Internet Protocol has two primary versions in use. Each version has its own definition of an IP address. Because of its prevalence, "IP address" typically refers to those defined by IPv4.

[edit] IP version 4

Main article: Addressing

IPv4 uses 32-bit (4 byte) addresses, which limits the address space to 4,294,967,296 (2³²) possible unique addresses. However, many are reserved for special purposes, such as private networks (~18 million addresses) or multicast addresses (~1 million addresses). This reduces the number of addresses that can be allocated as public Internet addresses, and as the number of addresses available is consumed, an IPv4 address shortage appears to be inevitable in the long run. This limitation has helped stimulate the push towards IPv6, which is currently in the early stages of deployment and is currently the only contender to replace IPv4.

Example: 192.168.1.1

[edit] IP version 5

Main article: IPv5

What would be considered IPv5 existed only as an experimental non-IP real time streaming protocol called ST2, described in RFC 1819. In keeping with standard UNIX release conventions, all odd-numbered versions are considered experimental, and this version was never intended to be implemented, thus not abandoned. RSVP has replaced it to some degree.

[edit] IP version 6

Main article: 128-bit length

In IPv6, the new (but not yet widely deployed) standard protocol for the Internet, addresses are 128 bits wide, which, even with a generous assignment of netblocks, should suffice for the foreseeable future. In theory, there would be exactly 2¹²⁸, or about 3.403 × 10³⁸ unique host interface addresses. The exact number is 340,282,366,920,938,463,463,374,607,431,768,211,456. This large address space will be sparsely populated, which makes it possible to again encode more routing information into the addresses themselves.

This magnitude of IPs available will be necessary in the future as mobile phones, cars and all types of personal devices come to rely on the internet for everyday purposes.