jaynes@med.umich.edu (William Jaynes) (02/25/91)
Someone felt that this problem may be a more general TCP protocol discrepancy
causing packets to be lost or ignored, so here is what I have posted elsewhere..
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Last week I noticed that messages to a particular host were being queued on
my mailhub. The sendmail message is
(Deferred: Connection timed out during result wait with uv1.im.med.umich.edu)
These messages never get delivered. All attempts fail until they time out and
are bounced.
The mailhub is a SunSLC. The host in question is a Vax running some
Wollengong TCP-IP/SMTP etc. software. Up until last week there was not a problem.
Both of us sys admins swear that we haven't changed anything. (of course)
Here are some facts:
- A short message (less then about 1100 bytes) will be delivered.
A longer message will not.
- I forced my Suns (4.1 and 4.1.1) to skip the mailhub and mail direct
and got the same results: longer messages were queued with the same
deferred message.
- I forced my Decs (Ultrix 4.0) to skip the mailhub and mail direct
and did NOT get the same results. Mail worked fine.
- From my Suns, if I telnet to port 25 of the Vax and fake mail, I can
send as big a message as I want.
- From Suns that are not on my net (141.214) and which mail direct to the
Vax, I can send as big a message as I want. (One is 4.0.3c)
- This one Vax is the ONLY host with which there is a problem.
Other Vaxen on the same ethernet don't have a problem. (I don't know
if the other Vaxen use the same SMTP software.)
- The data files are properly terminated with a 0x0a.
Using a Sniffer, I looked at packets during delivery attempts that failed.
The Suns simply aren't sending a <CR><LF>.<CR><LF> after the data is
sent. Instead they send the data again and again until the connection
times out. But they do send <CR><LF>.<CR><LF> on the short messages.
Why this one Vax? Why the Suns and not the Decs? What's going on?
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I have since seen that the SUNs and DECs are conifgured NOTRAILERS.
Doing an ifconfig on the VAX doesn't give a reference to trailers.PIRARD%vm1.ulg.ac.be@CUNYVM.CUNY.EDU (Andr'e PIRARD) (02/27/91)
On Mon, 25 Feb 91 15:33:52 GMT William Jaynes said: >(Deferred: Connection timed out during result wait with uv1.im.med.umich.edu) >These messages never get delivered. All attempts fail until they time out and >are bounced. >The mailhub is a SunSLC. The host in question is a Vax running some >Wollengong TCP-IP/SMTP etc. software. Up until last week there was not a A problem we've had seems just faintly related, but might help. A Ultrix host was repeatedly trying to send to a Sun what appears to be the end part of a mail item, until the 3-days limit expired. [ub4b.cs.kuleuven.ac.be to georges.montefiore.ulg.ac.be] 19 lines from a dest queue file w/o control starting (probably spilled here): returns the network address and name of all the subscribers. If you do not wish your name to be available to others in this fashion, just issue a "SET MACMAIL -- etc..., end of quote -- On each and every attempt, the Sun's sendmail was producing a core dump. I am in charge of none of those hosts, just routing in between. The problem may have be started by a longer than usual outage of routers in test. Yet. Andr'e PIRARD SEGI, Univ. de Li`ege B26 - Sart Tilman B-4000 Li`ege 1 (Belgium) pirard@vm1.ulg.ac.be or PIRARD%BLIULG11.BITNET@CUNYVM.CUNY.EDU