Lectures notes for 2010 - KTH

Trivial File Transfer Procotol (TFTP)
TFTP uses UDP (unlike FTP which uses TCP)
• simple and small
• requires only UDP, IP, and a device driver - easily fits in ROM
• a stop-and-wait protocol
• lost packets detected by timeout and retransmission
• Two operations:
• Read Request (RRQ)
• Write Request (RRQ) - for security reasons the file must already exist
• The TFTP server (“tftpd”) is generally run setrooted (i.e., it only has
access to is own directory) and with a special user and group ID -
since there is no password or other protection of the access to files via
TFTP!
• TFTP request is sent to the well know port number (69/udp)
• TFTP server uses an unused ephemeral port for its replies
• since a TFTP transfer can last for quite some time - it uses another port; thus freeing up the
well known port for other requests
Maguire Trivial File Transfer Procotol (TFTP) 4: 41 of 74
maguire@kth.se 2010.03.21 Internetworking/Internetteknik