TFTP is a simple protocol to transfer files, and therefore was named the Trivial File Transfer Protocol or TFTP. It has been implemented on top of the Internet User Datagram protocol (UDP or Datagram)  so it may be used to move files between machines on different networks implementing UDP. (This should not exclude the possibility of implementing TFTP on top of other datagram protocols.) It is designed to be small and easy to implement. Therefore, it lacks most of the features of a regular FTP. The only thing it can do is read and write files (or mail) from/to a remote server. It cannot list directories, and currently has no provisions for user authentication. In common with other Internet protocols, it passes 8 bit bytes of data.
Three modes of transfer are currently supported: netascii (This is ascii as defined in "USA Standard Code for Information Interchange"  with the modifications specified in "Telnet Protocol Specification" .) Note that it is 8 bit ascii. The term "netascii" will be used throughout this document to mean this particular version of ascii.); octet (This replaces the "binary" mode of previous versions of this document.) raw 8 bit bytes; mail, netascii characters sent to a user rather than a file. (The mail mode is obsolete and should not be implemented or used.) Additional modes can be defined by pairs of cooperating hosts.
Reference  (section 4.2) should be consulted for further valuable directives and suggestions on TFTP.