IP address: Difference between revisions

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)—in simpler terms, a computer address. Any participating network device—including routers, computers, time-servers, printers, Internet fax machines, and some telephones—can have their own unique address. Also, many people can find personal information through IP addresses.

An IP address can also be thought of as the equivalent of a street address or a phone number (compare: VoIP(voice over (the) internet protocol)) 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.

IP header size is 20 bytes.

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.

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

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.

IP version 6

Main article: 128-bit length

(32BYTE)

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, will more than 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 enormous magnitude of available IPs will be plenty large enough for the indefinite future, even though mobile phones, cars and all types of personal devices are coming to rely on the Internet for everyday purposes.

IP version 6 private addresses

Just as there are addresses for private, or internal networks in IPv4 (one example being the 192.168.0.1 - 192.168.0.254 range), there are blocks of addresses set aside in IPv6 for private addresses. Addresses starting with FE:80 to FE:FF (or "1111 1110 1" as the first nine bits) are to be used in private networks, and are non-routable.

See also

• Ping
• IP Multicast
• MAC address
• Regional Internet Registry
  • African Network Information Center
  • American Registry for Internet Numbers
  • RIPE Network Coordination Centre
  • Asia-Pacific Network Information Centre
  • Latin American and Caribbean Internet Addresses Registry
• Subnet address
• Geolocation
• Geolocation software
• Geo (marketing)
• Honeypot
• Data mining
• IP address spoofing
• Help:Page history: your IP in the Wikipedia page histories.
• Private network

External links

• Template:Dmoz
• Articles on CircleID about IP addressing
• IP-Address Management on LANs — article in Byte magazine
• Understanding IP Addressing: Everything You Ever Wanted To Know
• LookupCrap.com Learn a lot of information about a specific IP address

RFCs

• IPv4 addresses: RFC 791, RFC 1519, RFC 1918
• IPv6 addresses: RFC 4291