Mon, 11 Jul 88 21:06:21 EDT
> From: email@example.com (William C. VerSteeg)
> Subject: TFTP mode strings
> There appears to be some discrepancy between the TFTP document (IEN
> 133) and the packages that I have seen in use.
Um, try reading RFC783 (June 1981) for the definitive (ugh) tftp
> Basically, the IEN calls for three type of files- netascii, binary, and mail.
TFTP encodes "netascii", "octet" or "mail" into the request packet. I've
never seen "mail" implemented. Image, binary & test were never encoded
in the packet and were just used for user-interface/debugging purposes.
The thing to watch out for are retransmit wars. You can get into a mode
where you are transmitting two packets for each packet you really want
to send if you blindly ack all the packets that are retransmitted. I wound up
just relying on a timer and ignoring the retransmits.
Be careful of some older TFTP implementations. There was a bug in the
4.2 TFTP that made it confused when it received retransmitted packets.
Since 4.2 begat such a large amount of derivitives, some implementations
may still exhibit this problem. The problem was fixed in 4.3.
There are lots of implementations existing to test against. Have fun.
PC/IP @ Maryland
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