atically assign a private IP address from within this range, enabling the computer to communicate within the private network. Internet Protocol Version 6 (IPv6) With 32 bits, a total of 232 or 4.29 billion IP addresses are possible - more than enough one would think for all the computers that the human population could possibly want to interconnect. However, the famous statements that the world demand for computers would not exceed five machines, probably incorrectly attributed to Tom Watson Sr., chairman of IBM in 1943, or the statement of Ken Olsen, founder of Digital Equipment Corporation (DEC), to the 1977 World Future Society convention that "there is no reason for any individual to have a computer in his home", remind us how difficult it is to predict the growth and diversity of computer applications and usage. Chapter Two The industry is now working on IP version 6, which will give 128-bit IP addresses based on the thinking that a world population of 10 billion by 2020 will eventually be served by many more than one computer each. IPv6 will give a comfortable margin for future growth, with 3.4 X 1038 possible addresses - that is, 3.4 X 1027 for each of the 10 billion population, or 6.6 X 1023 per square metre of the earth's surface. It seems doubtful that there will ever be a need for IPv7, although, to avoid the risk of joining the short list of famously mistaken predictions of trends in computer usage, it may be as well to add the caveat "on this planet". Address Resolution Protocol As noted above, each PHY layer data transmission is addressed to the (Layer 2) MAC address of the network interface card of the receiving device, rather than to its (Layer 3) IP address. In order to address a data packet, the sender first needs to find the MAC address that corresponds to the immediate destination IP address and label the data packet with this MAC address. This is done using Address Resolution Protocol (ARP). Conceptually, the sending device broadcasts a message on the network that requests the device with a c