FTP:-
File Transfer Protocol is a network protocol used to transfer(copy) file from one host to another using Tcp/ip network . It is basically based on client server architecture model. It has 2 basic lines between the clint and server . One is called as Control line and another is Data line . Control line is used for the authentication . first this protocol authenticate the user by userneme and password through the control line by port no.21 . The second connection calld as Data connection opened then on port 20 . The data connection is used in 2 modes active and passive.If a firewall is existed then is used it passively. passively means that a new ip+port generated by the server to the client which used by server but its not client’s actual ip+port.In passive mode we use the command PASV to establish connection . In active mode simply the server gets the client’s ip+port for the file transfer.
when we authenticate the server request then server respond wth a three digit code to tell that your (client’s) last command was successfull then data line gets the control .Then file transfer in progress over the data connection. File transfer can be interrupted by sending a interrupt on the control line . The transfer rate of this protocol depends on the freq.,size of packts (transferring), bandwidth and traffic on the network.
