IP address - Internet Protocol Address – also known as an “IP number” or simply an “IP” is a numeric code that generally uniquely identifies a particular computer on the Internet. The format of an IP address is a 32-bit numeric address shown as 4 8-bit octets of numbers each and separated by dots. Each 8-bit octet is a number between 0 and 255. The first group is a number between 1 and 255 and the other groups are numbers between 0 and 255. IP addresses are combined into subnetworks (subnets). Subnets consist of 4-number IP addresses and can be of several classes that identify how many IP addresses are in one subnet. The smallest subnet is classless and has less then 255 IP addresses. The others can be of the following classes: C, B and A classes. Class C - first 3 octets are the same:
For example the following IP addresses are in the same C class subnet:
4.4.3.5 and 4.4.3.118
Class B - first 2 octets are the same:
4.4.3.5 and 4.4.7.45
Class A - first octet is the same:
4.2.4.6 and 4.87.97.110
Also there are classless subnets that are used to isolate subnets that are out of A, B and C classes. There are several subnets provided for private usage and has no route on the internet, so called private networks. They are 192.168.0.0/16; 172.16.0.0/15 and 10.0.0.0/8 - for use on a local area network (LAN) - or others (public) - for use on the Internet or other wide area network (WAN); static (also known as a permanent IP allocation; it is always the same and is associated as a characteristic of the local IP module) or dynamic (temporary IP address, which changes every time you connect to your ISP; usually it's dialup or DSL networks). Formally we've described current IP standard called IPv4 (based on number of octets) and new IP v6 standard are already in use/implementation. This newer IPv6 standard is planned to replace it and starting to be deployed. There are several organizations - regional Internet registries that assign Internet addresses for these 3 classes: ARIN, RIPE NCC, LACNIC and APNIC.
For more information regarding IP standardization and requirements, please, visit the following links:
http://tools.ietf.org/html/rfc950
http://tools.ietf.org/html/rfc1812
http://tools.ietf.org/html/rfc917
http://tools.ietf.org/html/rfc1101
http://tools.ietf.org/html/rfc1878
