Drop TFTP_MTU to 1440. This gives TFTP_LARGE_BLK = 1408 = 0x580, which
is the roundest number without dropping the MTU significantly below the
standard Ethernet MTU.
; For Ethernet MTU is normally 1500. Unfortunately there seems to
; be a fair number of networks with "substandard" MTUs which break.
; The code assumes TFTP_LARGEBLK <= 2K.
-TFTP_MTU equ 1472
+TFTP_MTU equ 1440
TFTP_LARGEBLK equ (TFTP_MTU-20-8-4) ; MTU - IP hdr - UDP hdr - TFTP hdr
; Standard TFTP block size
TFTP_BLOCKSIZE_LG2 equ 9 ; log2(bytes/block)