Internet Protocol Next Generation (IPv6)

摘要

Internet Protocol (IP) is the most widely used method for transporting datawithin and between communications networks. It is as useful for the growing field of intranets (networks internal to an enterprise or organization and not connected to the outside world-e.g., a network used for classified processing) as it is for the geographically distributed, highly heterogeneous Internet. IP combines the functions of internode linking with those of links between physical networks to provide communications paths between nodes on different networks. IP provides a connectionless, unreliable, best efforts packet delivery system. The concept of 'best efforts' delivery means that packets will not be discarded arbitrarily, without good cause. The cause of erratic packet delivery under a 'best efforts' commitment is normally exhaustion of resources or failure of a lower level link or physical system. IP is called connectionless because it resembles the Postal Service or Western Union more than it does the telephone system. When a node using IP wishes to send a message to another such node, it simply sends the packet, properly addressed, analogous to mailing a letter or sending a telegram. In IP's connectionless design, every packet is treated completely independently from all others.