FTP – File Transfer Protocol

Last Modified: March 2, 2024

Introduction

File transfer is one of the most common and essential tasks in computer networks. Whether downloading a file from a website, uploading a file to a cloud service, or sending an email attachment, file transfer is involved in some way. But have you ever wondered how file transfer works and what are the protocols and mechanisms via which file transfer takes place over the internet?

In this blog, we will explain the most widely used file transfer protocol, i.e., FTP in computer networks.

What is FTP Protocol (File Transfer Protocol)?

FTP stands for File Transfer Protocol. The TCP/IP network allows the transfer of files between two computers through a widely accepted network protocol. FTP came in the early 1970s and has been updated since then. The current version of FTP is defined in RFC 959.

FTP is widely used for transferring web pages, software updates, and other data over the Internet. It can also be used for downloading files to computer from other servers.

Even while moving data between systems is relatively easy and uncomplicated, there are situations when it can go wrong. For instance,

The file conventions between two systems could be different.
Text and data may be represented differently by two separate systems.
Separate directory structures could exist on two separate systems.

These issues are solved by the FTP protocol by creating two connections between hosts. Data transfer takes place over one connection, and the control connection occurs over a different connection.

How FTP Protocol works?

FTP in computer networks operates on a client-server model. The client requests to access the file stored on the server, and the server responds to the client’s request and sends the respective file. The client and the server communicate using two types of connections. These are –

Control connection
Data connection

Control Connection

The client and server communicate to send and receive commands through the control connection. FTP uses a control connection to transmit information such as user name, password, remote directory change commands, file retrieval, storage instructions, etc. It is initiated via port 21.

Data Connection

The data connection allows the transfer of file data between the client and server. It is initiated via port 20. FTP works via two different modes. These are:

Active Mode: When a client starts a session through a command channel, the server initiates a data connection and begins exchanging information with the client.
Passive Mode: The server sends the client the necessary information to initiate a data channel through the command channel. To avoid being blocked by firewalls and NAT routers, the client always uses passive mode while making connections.

A typical FTP protocol works as:

The client establishes a control connection to the server using TCP port 21.
The client sends a username and password to the server.
The client sends commands to navigate to the desired directory on the server.
The client requests a data connection mode (active or passive) from the server.
The client and the server establish a data connection using TCP port 20 (active mode) or a random port (passive mode).
The client sends commands to transfer files to or from the server over the data connection.
The client closes the data connection after the file transfer is complete.
The client sends a command to terminate the control connection.

Purpose of FTP in computer networks

FTP is designed to transfer files over networks with different operating systems, file systems, or architectures. Users using FTP in computer networks are able to access and alter files located on distant computers without worrying about the specifics of how the data are being moved or stored.

FTP Protocol is used for a variety of purposes, some of these are:

Backup: FTP can be used to back up files from one computer to another.
Software distribution: FTP can be used to download software updates or patches from a vendor’s server.
Access and Data loading: FTP is frequently utilized to gain access to shared web hosting and cloud services, aiming to transfer data onto a server located remotely.

Types of FTP Protocol

There are several varieties of file transfer protocols available. Some of these are:

Secure FTP (SFTP)

SFTP stands for The SSH File Transfer Protocol. SFTP is a layer above SSH that provides all the security and authentication capabilities of SSH. This protocol is rapidly replacing FTP/S and has already overtaken legacy FTP. It provides the full range of features available via these protocols with high reliability and higher levels of security.

Trivial FTP (TFTP)

TFTP is a simplified version of FTP that uses UDP instead of TCP for data transfer. Not all programs can use TCP because of its complexity and the features they don’t require. Regarding client-server interactions, TFTP’s simple structure and low cost make it suitable. TFTP is limited to File Transfer only and does not permit authentications.

TFTP is mainly used for bootstrapping network devices or transferring small files.

File Transfer Protocol Secure (FTPS)

File Transfer Protocol Secure (FTPS) is the secured variant of FTP, similar to Hypertext Transfer Protocol Secure. Transport Layer Security (TLS) and secure socket layer (SSL) safeguard these protocols. Using FTPS, companies may establish encrypted connections with their clients, partners, and end-users.

FTPS can encrypt either the control connection only (explicit FTPS) or both the control and data connections (implicit FTPS).

Hypertext Transfer Protocol (HTTP)

Hypertext Transfer Protocol, or HTTP, is a popular way to exchange data in the corporate world. This protocol is very easy to implement for server-to-client and client-to-client file transfers. The HTTP protocol is vulnerable to firewall-related challenges. However, compared to FTP, it is fundamentally insecure and lacks the ability to ensure data security and regulatory compliance. This protocol is implemented in situations where security concerns are not a factor.

File Transfer Protocol Commands

Here are the FTP Commands –

FTP Commands	Description
!	It allows shifting between operating systems and FTP.
?	It allows to print information about FTP commands.
append	It allows joining two files together.
ascii	It allows converting the file share mode to ASCII and is the default mode for many FTP programs.
binary	It fixes file share mode to binary.
bell	This command is used to alert by bell sound when any command is executed.
bye	It allows to exit and terminate the FTP session.
cd	It allows modification of the remote system’s directory.
close	It allows terminating FTP connections to remote systems.
dir	It allows to receive a list of contents in a remote directory.
delete	It allows deleting a file from the currently open remote directory.
debug	It allows activating and turning off debugging mode, and this command does not require a remote system connection.
disconnect	It allows terminating the FTP session.
FTP	It allows access to the FTP interpreter.
get	It allows to creation of duplicate data (one file) from the server to the client device.
hash	It allows a client to request a cryptographic hash of a file from the server-side FTP process.
help	It allows local help information to be presented. This command does not need a remote system connection.
lcd	It allows changes to be made to directories on your local system.
literal	It shares the argument with the remote system.
ls	It allows to present a list of names of files in the current remote directory.
mdelete	It allows deleting most files at once.
mdir	It allows listing the contents of multiple remote directories.
mget	It allows duplicating multiple data files from a remote computer to a local computer.
mkdir	It allows the creation of a new directory within an existing remote directory.
mls	This command shows a list of file names in multiple server directories.
mput	It allows multiple files to be duplicated from a user device to a server device.
open	This command allows the creation of a link with another computer system.
put	This command allows to duplication of a file from a user device to a server device.
pwd	It allows finding out the path name of the local directory of the remote system.
quit	It allows the FTP session to be terminated (like bye).
quote	It shares the argument with the remote system.
recv	It allows the recovery of files from a remote machine.
remotehelp	It allows for presenting remote system information.
rename	This command allows changing the name of a system file.
rmdir	It allows removing a directory from a local remote directory.
send	This command allows sending files.
status	This command allows to show the current state of the system.
type	It allows specifying the file share type.
user	This command shares the details of the new user.
verbose	It allows to turn verbose on/off.

These are the commands of File Transfer Protocol.

FTP Clients

An FTP client is a software that allows sharing of files by creating a connection between both the host computer and the remote server through the server’s domain, IP address, username and password. It enables the transmission of data and files in both directions between two computers that have a TCP network or Internet connection. It works on a client/server model where the host computer acts as the client and the remote FTP server acts as the central server.

Below are some of the following FTP clients:

FileZilla: FileZilla is an open-source and free FTP client. It provides support for FTP, FTPS, and SFTP on Windows, macOS, and Linux.
Transmit: Transmit is a macOS FTP client, and it provides support for FTP and SSH.
WinSCP: It is a free SSH file share protocol available for Windows FTP clients that provides support for FTP, SSH, and SFTP.
WS_FTP: It is another FTP client for Windows, and it provides support for SSH.

How to use File Transfer Protocol

There are three common ways to use FTP:

Web Browser: You can download files from servers through a web browser that provides FTP sites without any special software or clients.
GUI (General User Interface) FTP clients: Third-party applications allow users to connect and then share files over FTP.
Command-line FTP: FTP client capabilities equipped as a command line in major operating systems.

Advantages of File Transfer Protocol

FTP protocol has several advantages as a file transfer protocol, such as:

FTP can transfer large files

The feature of FTP protocol to transmit a vast number of files, regardless of their size, is its most useful feature. When you need to transfer terabytes of data all at once, FTP can manage the task both effortlessly and quickly, avoiding inefficiencies and lost time in the process.

FTP can transfer multiple directories at once

Enhance your workflow efficiency by transmitting multiple directories simultaneously without the need for frequent monitoring of the transfer progress. Additionally, you can transmit individual files or directories as needed. It is possible to continue working while the transfers occur in the background.

You have control over your transfers

FTP in Computer networks allow the user to resume a disrupted transfer in case of a lost connection without initiating the process. Certain FTP clients offer the capability to schedule data transfers, allowing users to determine the degree of automation they desire.

You can use FTP for WordPress management

FTP is also essential for working with WordPress sites. Because it establishes a direct link to the site’s files, you can perform things like installing and deactivating WordPress plugins and themes by hand or make modifications to the core WordPress files. Likewise, FTP may be used to identify and fix typical website problems, including incompatibility with external resources, conflicts between themes, and internal server failures.

Disadvantages of FTP Protocol

There are several disadvantages of using FTP (File Transfer Protocol). Here are some of the key drawbacks:

Lack of Security: FTP transfers data in plain text, making it vulnerable to interception and unauthorized access.
Firewall and NAT Issues: FTP’s separate control and data connections can cause problems when passing through firewalls and NAT devices.
Lack of Error Checking: FTP lacks built-in error checking and resuming capabilities, requiring entire file transfers to restart if interrupted.
Limited Scalability: FTP struggles to handle high loads and large numbers of concurrent connections efficiently.
Lack of Standardization: FTP Protocol variations and extensions can cause compatibility issues between different clients and servers.

Security Challenges of FTP

The File Transfer Protocol was never meant to be a secure channel for sensitive data. That’s why we don’t encrypt anything. It is not necessary for a hacker to decipher encryption in order to see or modify data during an FTP transmission. If the provider’s system is hacked, the data might be intercepted and used even if you utilize FTP cloud storage.

Since FTP data moves at a slower pace, it is more vulnerable to attacks such as spoofing, sniffer, and brute force. Hackers can examine an FTP transmission with the help of a port scan. Clear-text passwords, which are not encrypted, are one of FTP’s most serious security flaws.

Frequently Asked Questions

Q1 – How Does FTP Work?

With FTP, you may send data over the Internet. The use of FTP requires access to the Internet. When a file is downloaded, it is sent from a server to the receiving device, but when it is uploaded, it is sent from the receiving device to the server.

Q2 – Does FTP Use TCP or UDP?

For transport purposes, FTP only relies on the usage of the transmission control protocol (TCP) rather than the user datagram protocol (UDP).

Q3 – What is FTP used for?

File Transfer Protocol (FTP) allows data exchange between computers connected through a Transmission Control Protocol (TCP) network, such as the Internet.

Q4 – What is FTP in Linux?

The establishment of an FTP connection between two machines in Linux can be achieved through the utilization of the command “ftp.”

Conclusion

FTP in computer networks is a prominent protocol for transferring files over a network. FTP operates on the client-server model and uses two separate channels for communication: a control channel and a data channel.

In this blog, we have covered the basic definition of FTP, its working, the purpose of using FTP, different types of FTP, its advantages, and challenges. We hope you liked it. FTP – File Transfer Protocol is an integral part of CCNA Course. So, if you want to learn more, you can also check out the CCNA Course. Do let us know about your experience in the comment box.