Question

Discuss FTP(File Transfer Protocol), including all relevant terms in your explanation.

Answer 1

File Transfer Protocol(FTP):

• FTP stands for File Transfer Protocol.
• It is a standard internet protocol provided by TCP/IP used for transmitting the files from one host to another.
• It is mainly used for transferring the web page files from their creator to the computer that acts as a server for other computers on the internet.
• It is also used for downloading the files to compute from other servers.

Objectives of FTP:

• It provides the sharing of files.
• It is used to encourage the use of remote computers.
• It transfers the data more reliably and efficiently.

Features of FTP:

• Data representation
• File organization and Data structures
• Transmission modes
• Error control
• Access control

File operation:

• FTP uses client/server model for communication.
• Two TCP connections are used for file transfer.
• On one connection control signals (commands and responses) are exchanged and the other connection is used for actual data transfer.The two connections are called control connection and data connection.

Control connection:

• For sending control information like user identification,password,commands to change the remote directory,commands to retrieve and store files,etc ftp makes use of control connection.
• The control connection is initiated on port number 21.

Data connection:

• For sending the actual file,FTP makes use of data connection.
• A data connection is initiated on port number 20

FTP session:

• When FTP session is started between a client and servers,the client initiates a control TCP connection with the server side.The client sends control information over this.When the server receives this,it initiates a data connection to the client side.Only one file can be sent over one data connection.FTP needs to maintain a state about its user throughout the session.

Data Structures:

FTP allows 3 types of data structures.

• File structure: It is continuous sequence of data bytes.
• Record structure:In this,the file is made up of sequential records.
• page structure:In this,the file is made up of independent indexed pages.

FTP Servers:

To separate the general public users from the more private users,FTP servers are divided into 2 parts:

• Anonymous Server: FTP sites that allows anonymous FTP do not require a password for access.You only have to log in as anonymous and enter your email address as password.
• Non-anonymous server:If you use a non-anonymous server,then you will log in as yourself and give your password.

FTP Clients:

• FTP runs on client/server model.For using FTP you need client software to run your PC.
• To begin an FTP session,you run the FTP client software and contact the FTP server from where you want to download files from.

FTP commands:

Some of the FTP commands are:

USER - This command sends the user identification to the server.

PASS - This command sends the user password to the server.

PWD - This command causes the name of the current working directory to be returned in the reply.

Working Procedure:

Clients initiate a conversations with servers by requesting to download a file.Using FTP, a client can upload,download,delete,rename etc and copy files on a server.A user typically needs to log on to the FTP server to use the available content.

Advantages of FTP:

• speed
• Efficient
• Security
• Back & Forth movement

Disadvantages of FTP:

• It is not compatible with every system.
• Attackers can quickly identify the FTP password
• Does not allow to run simultaneous transfers to multiple receivers.