The IP protocol provides a hierarchical, hardware-independent addressing system and offers the services necessary for delivering data on a complex, routed network. Each network adapter on a TCP/IP network has a unique IP address.
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Descriptions of TCP/IP often talk about a computer having an IP address. A computer is sometimes said to have an IP address because most computers have only one network adapter. However, computers with multiple network adapters are also common. A computer that is acting as a router or a proxy server, for instance, must have more than one network adapter and, therefore, has more than one IP address. The term host is often used for a network device associated with an IP address.