Definition of IP Address in My Version

IP address is a numerical identification (logical address) that is assigned to devices participating in a computer network utilizing the Internet Protocol for communication between its nodes. The role of the IP address has been characterized as follows:

A name indicates what we seek.
An address indicates where it is.
A route indicates how to get there.

The original designers of TCP/IP defined an IP address as a 32-bit number and this system named Internet Protocol Version 4 (IPv4). But a new addressing system (IPv6), using 128 bits for the address, was developed. IPv4 uses 32-bit (4-byte) addresses, which limits the address space to 4,294,967,296 possible unique addresses. IPv4 addresses are usually represented in dot-decimal notation. Each part represents 8 bits of the address, and is therefore called an octet. It is possible, although less common, to write IPv4 addresses in binary or hexadecimal. When converting, each octet is treated as a separate number. (So 255.255.0.0 in dot-decimal would be FF.FF.00.00 in hexadecimal.)

Network administrators interpreted an IP address as a structure of network number and host number. The highest order octet were designating the network number, and the rest of the bits were called the rest field or host identifier and used for host numbering within a network. This method soon proved inadequate as local area networks developed that were not part of the larger networks already designated by a network number.

The IP address is divided into two parts: the network address and the host identifier. The subnet mask (in IPv4 only) prefix determine how the IP address is divided into network and host parts. The term subnet mask is only used within IPv4. the IP address is followed by a slash and the number (in decimal) of bits used for the network part, also called the routing prefix.

The Internet addressing specification was revised with the introduction of classful network architecture. Classful network design allowed for a larger number of individual assignments. The first three bits of the most significant octet of an IP address was defined as the “class” of the address, instead of just the network number and, depending on the class derived, the network designation was based on octet boundary segments of the entire address.

Although classful network design was a successful developmental stage, it proved unscalable in the rapid expansion of the Internet and was abandoned when Classless Inter-Domain Routing (CIDR) was introduced (RFC 1517, RFC 1518, RFC 1519) to define a new concept for the allocation of IP address blocks and new rules of routing protocol packets using IPv4 addresses.

Computers not connected to the Internet, such as office computer that communicate only with each other via TCP/IP, need not have globally-unique IP addresses. These addresses are not routed on the Internet, and thus need not be coordinated with an IP address registry.

The next generation of the Internet Protocol, aimed to replace IPv4 on the Internet, was eventually named Internet Protocol Version 6 (IPv6)[3] The address size was increased from 32 to 128 bits (16 bytes), which, even with a generous assignment of network blocks, is deemed sufficient for the foreseeable future. Mathematically, the new address space provides the potential for a maximum of 2128, or about 3.403 × 1038 unique addresses.

The new design also provides the opportunity to separate the addressing infrastructure of a network segment–that is the local administration of the segment’s available space–from the addressing prefix used to route external traffic for a network. The new design is not based on the goal to provide a sufficient quantity of addresses alone, but rather to allow efficient aggregation of subnet routing prefixes to occur at routing nodes. As a result, routing table sizes are smaller, and the smallest possible individual allocation is a subnet for 264 hosts, which is the size of the square of the size of the entire IPv4 Internet.

IPv6 has facilities that automatically change the routing prefix of entire networks should the global connectivity or the routing policy change without requiring internal redesign or renumbering. The large number of IPv6 addresses allows large blocks to be assigned for specific purposes and, where appropriate, to be aggregated for efficient routing.

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This entry was posted on Monday, November 24th, 2008 at 3:23 am and is filed under Personal Note. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.