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in Networking by (120 points)

3 Answers

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by (240 points)


FTP uses two TCP connections for communication. One to pass control information, and is not used to send files on port 21, only control information. And the other, a data connection on port 20 to send the data files between the client and the server. The connection has to be established before the files can actually be sent across. After which, the data starts transferring over the data connection on port 20.

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FTP is connection protocol
it uses 2 TCP

*1 - to control information it uses 20 port no.
*2 - to transfer the data between client and server over the network it uses 21 port no.

SFTP is secured connection
SFTP adss layer to FTP
It uses 22 port no.

SFTP use to encrypt the data over the network.
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by (930 points)
Ports like FTP and DHCP have two numbers because as we know the data communication can be allowed when there is a secured connection(not necessarily) between two computers ie a client and a server.

So FTP has two ports. Ports 20 & 21.

Port no 20 is used to pass control information. The data transmission deos not take place on this port number.

Likewise, port 21 is used for data transmission.

Hence the requirement of two ports.

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