ARP:(Address resolution protocol)
Networking H/W demands that a datagram contain the physical address of the intended recipient. If problem Address Resolution protocol (ARP) was developed. ARP takes the IP address of a host as input & gives its corresponding physical address as the output. As if doesn’t know who must be having address if sends the broadcast message to all the computer on the network. The computer whose IP address matches the broadcast IP address sends a reply and along with if, its physical address to the broadcasting computer. All other computers lignose the broadcast message as IP address is different Now, when it is responding whose IP address gets match is aware of the sender. So it doesn’t require sending broadcast message. As it knows sender hardware as well as IP address that the reason it uncast the reply so that senders only receive it.
FTP is a stranded mechanism provided by the Internet for copying a file from one host to the other.
Some of the problem in transferring files from one system to the other are as follows:
* Two systems may use different file name conventions.
* Two systems may represent text data in different types.
* The directory structure of the two systems may be different.
FTP provides a simple solution to all these problems.
FTP established two connections between the client and server. One is for data transfer and the other is for the control information.
The fact that FTP separates control and data makes it very efficient.
The control connection uses simple rules of communication. Only one line of command or a line of response is transferred at a time.
But the data connection uses more complex rules due to the variety of data types being transferred.
FTP uses port 21 for the control connection and port 20 for the data connection.