Computer and Communication Networks (paperback)

9.5. File Transfer and FTP

File transfer is another computer networking application. It is always essential that files and information geographically distributed over different locations be shared among the members of a working group . In a certain application, files are typically saved in a server. A user then uses a file transfer protocol to access the server and transfer the desired file. Two file transfer protocols are FTP and SCP.

9.5.1. File Transfer Protocol (FTP)

File Transfer Protocol (FTP) is part of the TCP/IP suite and is very similar to TELNET. Both FTP and TELNET are built on the client/server paradigm, and both allow a user to establish a remote connection. However, TELNET provides a broader access to a user, whereas FTP allows access only to certain files. The essence of this protocol is as follows .

1. A user requests a connection to a remote server.

2. The user waits for an acknowledgment.

3. Once connected, the user must enter a user ID, followed by a password.

4. The connection is established over a TCP session.

5. The desired file is transferred.

6. The user closes the FTP connection.

FTP can also run through a Web browser.

9.5.2. Secure Copy Protocol (SCP)

The Secure Copy Protocol (SCP) is similar to TELNET but is secure. Incorporated in the SCP structure are a number of encryption and authentication features that are similar to those in SSH. Also similar is the exchange of commands between local and remote hosts . SCP commands automatically prompt the user for the password information when it is time to access a remote machine. SCP cannot handle file transfer between machines of significantly different architectures.