SFTP is implemented through client and server software that is available for all commonly used computing platforms.
Trivial File Transfer Protocol (TFTP)
A variation on FTP is TFTP, which is also a file transfer mechanism. FTP and TFTP are both application layer protocols; however, TFTP does not have the rudimentary security capability or the level of functionality that FTP has. TFTP uses only UDP as a transport protocol, making it a connectionless protocol. As such, it has a lower overhead than FTP.
Another feature that TFTP does not offer is directory navigation. In FTP, commands can be executed to navigate around and manage the file system; TFTP offers no such capability. TFTP requires that you request not only exactly what you want, but also from what specific location.
Simple Mail Transfer Protocol (SMTP)
The SMTP protocol defines how mail messages are sent between hosts. SMTP is a connection-oriented protocol; it uses TCP connections to guarantee error-free delivery of messages. SMTP is not overly sophisticated and requires that the destination host always be available.
For this reason, mail systems spool incoming mail so that users can read it at a later time. How the user then reads the mail depends on how the client accesses the SMTP server. SMTP is an application layer protocol.Today, SMTP is often used to send email between servers, whereas another protocol such as POP3 or IMAP4 is used to download the email from the server to a client system.