http://www.rfc-editor.org/rfc/rfc7440.txt
RFC 7440: TFTP Windowsize Option, P. Masotta2015-01-01T23:00:00-00:00This document describes a TFTP option that allows the client and server to negotiate a window size of consecutive blocks to send as an alternative for replacing the single-block lockstep schema. The TFTP option mechanism employed is described in "TFTP Option Extension" (RFC 2347).