TABLE OF CONTENTS IP was designed in the 1970s for the purpose of connecting computers that were in separate geographic locations. Computers in a campus were connected by means of local networks, but these local networks were separated into essentially stand-alone islands. "Internet," as a name to designate the protocol and, more recently, the worldwide information network, simply means "internetwork," that is, a connection between networks. In the beginning, the protocol had only military use, but computers from universities and enterprises were quickly added. The Internet as a worldwide information network is the result of the practical application of the IP protocol, that is, the result of the interconnection of a large set of information networks [IPV200501]. Starting in the early 1990s developers realized that the communication needs of the 21st century needed a protocol with some new features and capabilities, while at the same time retaining the useful features of the existing protocol.
Although link-level communication does not generally require a node identifier (address) since the device is intrinsically identified with the link-level address, communication over a group of links (a network) does require unique node identifiers (addresses). The IP address is an identifier that is applied to each device connected to an IP network. In this setup, different elements taking part in the network (servers, routers, user computers, etc.) communicate with one another using their IP address as an entity identifier. In version 4 of the IP protocol, addresses consist of four octets. For ease of...
