Now before giving answer of first question I would like to give the answer of our second question. Let’s consider an application program that generates data to be sent across an internet, for this software places the data in the packet, which contains the protocol address (IP address) of the destination. Software in each host or router uses the protocol destination address to select the next hop for the packet. Once a next hop has been selected, software transfers the packet across one physical network to the selected host or router. To provide the illusion of a single, large network, software works with the IP addresses when forwarding the packets. Both the next hop and destination addresses are the IP addresses.
Now the main problem arises here, when we want to transmit frames across physical network hardware we need hardware address of the destination because the hardware does not understand the IP addressing. So, when a frame is set across a physical network it must use the hardware’s frame format and all the addresses in the frame must be hardware addresses. Consequently, the protocol address of the next hop must be translated to an equivalent hardware address before a frame can be sent. The process of converting IP address to its equivalent hardware address is known as Address Resolution and a protocol address is said to be resolved to the correct hardware address. Address Resolution is local to network that means one computer can resolve the address of another computer only if both computers attach to the same physical network. A computer never resolves the address of a computer on a remote network.
After this explanation I hope you understand a little bit about the Address Resolution Protocol. In the next post I will tell about the various techniques through which Address Resolution takes place. Hope you like this post.
If you have any doubts in any of the topics of Computer Networks then post your problem in the comment. I will try to sort it out.