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From: MILLS@USC-ISID.ARPA
Newsgroups: mod.protocols.tcp-ip
Subject: Re: Adaptive SMTP Timeouts
Message-ID: <8605302106.AA16597@ucbvax.Berkeley.EDU>
Date: Thu, 29-May-86 14:02:15 EDT
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Posted: Thu May 29 14:02:15 1986
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In response to the message sent  Thu, 29 May 86 12:15:38 +0100 from mcvax!dpk@seismo.CSS.GOV

Doug,

I commonly see delays of up to a minute for replies to SMTP commands
with MIT-MULTICS and up to two minutes for certain FORD-WDL hosts. This,
however, bogs the question, since delays of this magnitude would be considered
prima facie evidence of brain lesions by almost everybody except their
maintainers. On the other hand, premature abandonment of an SMTP connection
may be hazardous to the mental health of the recipients. In a recent case
when our local 4.2bsd prematurely abandoned an SMTP connection and repeatedly
tried it again hour after hour, the recipient got a (truncated) copy of the
message every time. After three days he became quite violent.

I think SMTP adaptive timeouts, while cute and possibly even useful in some
cases, should not be used to "tune" connections, but to ensure system
resources are returned to service when something hangs. They should be set
quite long - in the order of several minutes. The present situation clearly
indicates some implementations are broken and should be fixed. Having
said that, it also is clear that the error-recovery characteristics of
many mailers and femailers could be much improved.

Dave
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