Different File Transfer Protocols

TFTP : Trivial File Transfer Protocol

(TFTP) is a simple protocol to transfer files. It has been implemented on top of the User Datagram Protocol (UDP) using port number 69. TFTP is designed to be small and easy to implement, therefore, lacks most of the features of a regular FTP. TFTP only reads and writes files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication.

In TFTP the connection is opened and the file is sent in fixed length blocks of 512 bytes. Each data packet contains one block of data, and must be acknowledged by an acknowledgment packet before the next packet can be sent. A data packet of less than 512 bytes signals termination of a transfer.

It is often used by servers to boot diskless workstations, X-terminals, and routers. Due to its simple design, TFTP could be implemented using a very small amount of memory. It is therefore useful for booting computers such as routers which may not have any data storage devices. It is an element of the Preboot Execution Environment (PXE) network boot protocol, where it is implemented in the firmware ROM / NVRAM of the host's network card.

Due to the lack of security, it is dangerous to use it over the Internet. Thus, TFTP is generally only used on private, local networks.

FTP : File Transfer Protocol

FTP is a popular and fast way of moving files between a client and a server. FTP operates on the application layer of the OSI model, and is used to transfer files using TCP/IP. To do so, an FTP server has to be running and waiting for incoming requests. The client computer is then able to communicate with the server on port 21.

The problem with FTP is that it’s not secured by encryption, leaving files at risk of being compromised during transport. It does not take any precautions to protect information transmitted during a session. This includes your username, password, and any files transmitted.

FTPS : FTP-SSL/ File Transfer Protocol over SSL

File Transfer Protocol over SSL. FTPS is an encrypted flavor of the FTP protocol (kind of like how HTTPS is an encrypted flavor of HTTP).

FTPS is a real ftp that uses TSL/SSL to encrypt the control session and if required the data session. With FTPS the control session is always encrypted, but the data session might not be. Why is this? Because with the control session encrypted the authentication is protected and you always want this (normal ftp uses clear text). If you are NOT pre-encrypting the file, you want the data session encrypted so that the file is encrypted while the data is in flight. However, if you are pre-encrypting the file then you do not need to have the data connection encrypted as you do not need to add the overhead of encrypting the data connection, since the file is already encrypted.

Understand that SFTP is SSH file transfer and FTPS is FTP with SSL, FTPS is a file transport layer on top of SSL or TLS. The FTPS adds SSL-enabled FTP send and receive capabilities, uses the FTP protocol to transfer files to and from SSL-enabled FTP servers.

SFTP : Secure File Transfer Protocol/ SSH File Transfer Protocol/ Secret File Transfer Protocol

"sftp is an interactive file transfer program, similar to ftp, which performs all operations over an encrypted ssh transport".

SSH File Transfer Protocol. SFTP uses the Secure Shell (ie: SSH) protocol to encrypt all file transfer communications. SFTP is a bit more firewall friendly because it uses only 1 port and it’s also a bit more secure than FTPS. SFTP is gaining steam as the most preferred method of secure file transfer, particularly in infrastructures that favor unix but SFTP is quickly gaining steam in Windows environments as well.

It is a secure replacement for FTP (File Transfer Protocol) based on the Secure Shell protocol. Unlike FTP, SFTP encrypts both commands and data providing effective protection against common network security risks. SSH Client and Server provide both command-line SFTP tools and a graphical user interface for Windows users. SFTP encrypts the session, preventing the casual detection of your username, password or anything you've transmitted.

The major reason for implementing SFTP versus FTP is security. FTP is not even remotely secure. In FTP all data is passed back and forth between the client and server without the use of encryption. This makes it possible for an eavesdropper to listen in and retrieve your confidential information including login details. With SFTP all the data is encrypted before it is sent across the network.

SFTP is sometimes confused with Simple File Transfer Protocol but both are totally different.

SCP : Secure Copy

SCP is a non-interactive command-line tool for securely transmitting files from a machine to another. It is a secure replacement for RCP and provides a similar command-line syntax. SCP is strongly based on SFTP but is often a more suitable choice when setting up unattended file transfers using scripts.

The SCP protocol is a network protocol, based on the BSD RCP protocol, which supports file transfers between hosts on a network. SCP uses Secure Shell (SSH) for data transfer and utilizes the same mechanisms for authentication, thereby ensuring the authenticity and confidentiality of the data in transit. A client can send (upload) files to a server, optionally including their basic attributes (permissions, timestamps). Clients can also request files or directories from a server (download). SCP runs over TCP port 22 by default. Like RCP, there is no RFC that defines the specifics of the protocol.

Simple FTP : Simple File Transfer Protocol

As mentioned above Simple FTP is sometimes confused with Secure File Transfer Protocol, but both are totally different.

Simple File Transfer Protocol, was proposed as an (unsecured) file transfer protocol with a level of complexity intermediate between TFTP and FTP. It has some useful features not present in Trivial FTP (TFTP), but is not as powerful as FTP. SFTP supports user access control, file transfers, directory listing, directory changing, file renaming and deleting. It was never widely accepted on the internet, and is now assigned Historic status by the IETF.

Simple FTP uses only one TCP connection; whereas TFTP implements a connection over UDP, and FTP uses two TCP connections (one using the TELNET protocol). It runs through port 115. It has a command set of 11 commands and support three types of data transmission: ASCII, BINARY and CONTINUOUS.

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