Date: Tue, 14 Aug 2001 11:56:49 +0200 From: Gerhard Butscher <gerhard.butscher@esk.fhg.de> To: syslinux@linux.kernel.org, net@FreeBSD.ORG Subject: TFTP sorcerer's apprentice syndrome Message-ID: <3B78F5E1.475FF891@esk.fhg.de>
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Hello, I am using the linux (SuSE 7.0) tftp server with an embedded tftp client (running on an embedded target). I changed that client code and caused by that change a considerable amount of delay. And the Sorcerer's Apprentice Syndrome appeared: From that point where the server has sent a duplicate data packet (after the client's ACK timed out), there were always duplicate data (and of course ACK) packets until the end of the file transfer. I am not a protocol expert nor a unix programming expert but as far as I understand the tftp server code (e.g. tftp-hpa-0.21) there is a handling for duplicate ACK packets. But (maybe) not exactly the handling proposed by the RFC 1350. On paget 7 of RFC 1350 it is said: "All packets other than duplicate ACK's and those used for termination are acknowledged unless a timeout occcurs." So the strategy would be to discard the duplicate ACK and let the timer keep running. Not repeating the previous data packet - which I think is done in the existing code. The data packet would only be repeated in case of a timeout. I would appreciate if you could write a comment whether I am right or wrong or something in between. Best regards, Gerhard To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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