http://www.rfc-editor.org/rfc/rfc1782.txt
RFC 1782: TFTP Option Extension, G. Malkin, A. Harkin1995-03-01T23:00:00-00:00The Trivial File Transfer Protocol is a simple, lock-step, file transfer protocol which allows a client to get or put a file onto a remote host. This document describes a simple extension to TFTP to allow option negotiation prior to the file transfer.