Do you think IIT Guwahati certified course can help you in your career?
Introduction
This blog will discuss the FTP (File transfer protocol) in the application layer. FTP (File Transfer Protocol) is an application layer protocol that allows you to transfer data between local and distant file systems. Similar to HTTP, it runs on top of TCP. FTP uses two TCP connections in parallel to transfer a file: a control connection and a data connection.
What is File Transfer Protocol (FTP)?
File Transfer Protocol (FTP) is a standard network protocol used to transfer files between a client and a server over a network. It enables users to upload, download, and manage files efficiently. FTP operates on a client-server model and typically requires authentication via a username and password.
How FTP Differs from Other Protocols like HTTP
Focus on File Transfer – FTP is specifically designed for transferring large files, whereas HTTP is primarily used for web browsing and retrieving webpages.
Connection Type – FTP establishes a dedicated connection between the client and server, making it more efficient for bulk file transfers. HTTP, on the other hand, downloads files through a stateless request-response mechanism.
Authentication – Unlike HTTP, FTP requires login credentials for secure file access, though anonymous FTP access is also available.
File Formats Supported in FTP
ASCII (Text Files) – Used for transferring readable text-based files.
Binary (Executable & Media Files) – Used for non-text files like images, videos, and compressed archives.
Key Features of FTP
Supports Large File Transfers – Handles large files more efficiently than HTTP.
Two Modes of Transfer – Active and Passive mode for different network conditions.
Resumable Transfers – Allows users to pause and resume file transfers.
Multi-File Transfers – Can transfer multiple files simultaneously.
Directory Management – Enables users to create, delete, and modify directories remotely.
Encryption Support – Secure FTP (SFTP) and FTP over SSL (FTPS) provide enhanced security.
Types of FTP
File Transfer Protocol (FTP) offers various modes of file transfer, each tailored to different authentication, encryption, and security requirements. Understanding these types helps in selecting the appropriate method for secure and efficient file transfers.
Anonymous FTP: Allows users to access files without authentication. Commonly used for public file repositories, users log in with the username 'anonymous' and an email address as the password. This method offers minimal security and is suitable for non-sensitive data.
Password-Protected FTP: Requires users to authenticate with a valid username and password. This standard FTP method provides controlled access to files, ensuring that only authorized users can upload or download data. However, credentials and data are transmitted in plaintext, posing security risks.
FTP over SSL/TLS (FTPS): Enhances standard FTP by incorporating SSL/TLS encryption, securing both command and data channels. FTPS can operate in two modes:
Implicit FTPS: Establishes an SSL/TLS connection immediately upon connection initiation. This mode typically uses port 990 and requires all clients to use encryption.
Explicit FTPS: Starts as a standard FTP connection and upgrades to an encrypted connection upon client request using the "AUTH TLS" command. This mode offers flexibility, allowing both encrypted and unencrypted sessions over port 21.
SSH File Transfer Protocol (SFTP): Despite its name, SFTP is distinct from FTP and operates over the Secure Shell (SSH) protocol. It provides a secure channel for file transfer, encrypting both commands and data, thus preventing unauthorized access and data breaches. SFTP uses port 22 and is favored for its robust security features.
Trivial File Transfer Protocol (TFTP): A simplified version of FTP, TFTP lacks authentication and encryption mechanisms. It is primarily used for transferring small files within local networks, such as during network booting processes. Due to its minimal security features, TFTP is unsuitable for transferring sensitive data over public networks.
Selecting the appropriate FTP type depends on the specific security and functional requirements of the file transfer scenario.
Types of Connection in FTP
Control Connection
Data Connection
Control connection
FTP uses a control connection to communicate control information such as user identification, passwords, commands to update the remote directory, commands to receive and save files, etc. On port number 21, the control connection is established.
Data connection
FTP uses a data connection to send the real file. On port number 20, a data connection is established.
Because FTP uses a separate control connection, the control information is sent out-of-band. Some protocols send the data and the request and response header lines over the same TCP connection. Sending information over the same TCP connection is an in-band transfer of information. HTTP and SMTP are two examples of this.
When a client and server establish an FTP session, the client initiates a control TCP connection with the server. Over this, the client sends control information. When the server receives this information, it initiates a data connection with the client. Over a single data connection, just one file can be transmitted. The control connection, on the other hand, is kept active throughout the user session. HTTP is stateless, which means it does not need to keep track of any user state. However, FTP must keep track of its user's state during the session.
FTP Clients
FTP operates on a client-server model, where the client initiates a connection to an FTP server to transfer files. Users can interact with FTP servers using command-line interfaces, graphical FTP clients, or web browsers. FTP clients provide an interface for users to upload, download, rename, delete, and manage files on remote servers.
Popular FTP Clients
FileZilla – A free, open-source FTP client with an easy-to-use graphical interface.
WinSCP – Supports FTP, FTPS, and SFTP for secure file transfers.
Cyberduck – A cross-platform client for FTP and cloud storage integration.
Core FTP – Provides secure FTP solutions with encryption support.
FTP clients simplify file transfers between local and remote systems, making them essential for web hosting, backups, and large-scale file management.
Data Structures
Three types of data structures are allowed over FTP.
1. File Structure: There is no internal structure in the file structure, and the file is handled as a continuous sequence of data bytes.
2. Record Structure: The file is made up of sequential records in a record structure.
3. Page Structure: The file is made up of independent indexed pages in page structure.
FTP commands
Given are a few of the FTP commands:
FTP Data Types
FTP supports different data types to define how files are represented and transmitted over the network. These data types ensure compatibility between different systems and help in efficient file transfers. The choice of data type depends on the nature of the file being transferred, whether it contains text, binary data, or structured records.
Types of FTP Data Transfers
ASCII Mode (Text Mode)
Used for transferring plain text files such as .txt, .html, and .csv.
Converts end-of-line characters between different operating systems (e.g., Windows uses CRLF, while Unix uses LF).
Not suitable for binary files, as it may corrupt non-text data.
Binary Mode (Image Mode)
Used for transferring non-text files such as images, videos, executables, and compressed files.
Transfers data byte-by-byte without modification, ensuring no loss or corruption.
Essential for files like .jpg, .mp3, .zip, and .exe.
EBCDIC Mode
Used for file transfers between systems that use the Extended Binary Coded Decimal Interchange Code (EBCDIC).
Commonly used in IBM mainframe environments.
Local Mode
Allows file transfers between two systems using identical character sets without conversion.
Useful for specialized hardware or unique file formats.
Compressed Mode
Reduces file size during transmission by using run-length encoding (RLE).
Improves speed and efficiency, especially on slow networks.
Selecting the correct FTP data type is crucial to ensure files are transmitted accurately without corruption.
FTP Replies
Given are a few of the FTP replies:
Characteristics of FTP
File Transfer Protocol (FTP) is a standard network protocol used to transfer files between a client and a server over the internet or a local network. It operates on a client-server model and supports authentication for secure access. FTP is widely used for website management, file sharing, and remote file storage. Below are the key characteristics of FTP:
Client-Server Architecture
FTP follows a client-server model where the client requests files, and the server provides access.
Users connect to an FTP server using FTP clients like FileZilla, WinSCP, or Cyberduck.
Authentication and Security
FTP allows user authentication through a username and password or anonymous access.
Secure FTP versions like FTPS (FTP Secure) and SFTP (SSH File Transfer Protocol) add encryption for data protection.
Supports Active and Passive Modes
In active mode, the client opens a port and waits for the server to connect.
In passive mode, the client requests the server to open a port, making it firewall-friendly.
Multiple File Transfer Modes
FTP supports ASCII (text mode) for text-based files and Binary mode for media and executable files.
It ensures efficient data transfer by preserving file formats across different operating systems.
Directory and File Management
Users can perform operations like uploading, downloading, renaming, deleting, and creating directories remotely.
Commands like LIST, RETR, and STOR help in managing files on the server.
Resume and Parallel Transfers
FTP supports resuming interrupted file transfers, preventing data loss in case of network failure.
Some FTP clients allow parallel transfers, improving efficiency by uploading or downloading multiple files simultaneously.
FTP remains an essential protocol for file transfer, ensuring reliable, structured, and efficient data exchange over networks.
Features of FTP
FTP is primarily used to send a single file at a time.
FTP can also list files, create and delete directories, delete files, rename files, and conduct a variety of other tasks.
FTP also conceals the details of host systems.
It is a connection-oriented protocol.
FTP is a stateful protocol because, in this protocol, a control connection is initiated by the client for the life/duration of an FTP session, which usually spans numerous data transfers.
Advantages of FTP
FTP is simple to implement.
FTP is one of the most efficient methods for transferring files from one computer to another.
FTP is a standard protocol and is used widely.
FTP is more efficient since it eliminates the need to do all operations in order to obtain the entire file.
Disadvantages of FTP
The File Transfer Protocol is not a secure method of data transfer.
FTP has a file size limit. Only files up to 2 GB in size can be transferred.
The FTP does not support multiple receivers.
The data is not encrypted when transferred through FTP.
Difference Between FTP and SFTP
FTP (File Transfer Protocol) and SFTP (Secure File Transfer Protocol) are both used for transferring files between a client and a server. However, they differ in terms of security, data transmission, and authentication methods. FTP is a standard protocol that transfers files in plain text, while SFTP provides encryption and secure authentication to protect sensitive data.
Feature
FTP (File Transfer Protocol)
SFTP (Secure File Transfer Protocol)
Security
Transfers data in plain text, making it vulnerable to attacks.
Encrypts both commands and data, ensuring secure transmission.
Encryption
No encryption; data is sent as is.
Uses SSH (Secure Shell) encryption to protect data.
Authentication
Requires username and password, which are sent in plain text.
Uses SSH keys and password-based authentication for added security.
Data Transfer Speed
Generally faster because it does not encrypt data.
Slightly slower due to encryption overhead.
Port Used
Uses port 21 for communication.
Uses port 22, the same as SSH.
Firewall Compatibility
Difficult to configure behind firewalls due to multiple ports used.
Easier to use behind firewalls as it operates over a single connection.
File Integrity
No built-in mechanism for checking file integrity.
Supports checksum verification for file integrity.
You can read related articles such as Congestion Control in Computer Networks here.
Frequently Asked Questions
List all layers of the OSI model.
There are seven layers in the OSI model. They are: 1. Physical layer
2. Data link layer
3. Network layer
4. Transport layer
5. Session layer
6. Presentation layer
7. Application layer
Which are the protocols used in the Application layer?
Several protocols are used in the Application layer which include DNS, SMTP, POP, FTP, HTTP, etc.
What is SMTP protocol?
SMTP (Simple Mail Transfer Protocol) is an application layer protocol. It is used to send mails
List the most common network topologies?
The most common network topologies are: 1. Mesh topology
2. Bus topology
3. Star topology
4. Ring topology
Conclusion
In this article, we discussed FTP (File Transfer Protocol), its features, advantages, and disadvantages. FTP remains a widely used method for efficient file transfers between systems, especially for large files and automated processes. However, its lack of built-in security makes it unsuitable for sensitive data exchanges. To enhance security, safer alternatives like SFTP and FTPS should be considered. Despite these drawbacks, FTP continues to be a reliable and stable solution for file management across diverse networks, making it essential to understand its functionalities and limitations for secure and efficient file transfers.
34+ registered 
