Hi Guys
Not sure if I'm asking the right people, or even the right question, but I'm
willing to try anything right now.
This problem started a couple of days ago and it's taken me until this morning
to get a handle on it. We have a 2Mbps ADSL connection shared between 25 users
for web browsing and e-mail. We have our own SMTP mailer inhouse that forwards
all outgoing mail to our ISP. A couple of days ago people started to complain
that web browsing was okay one moment, but unusably slow the next. Pinging one
of our ISPs nameservers during a slow period showed average response times of
2500ms where we normally have 30ms. The connection is still alternating between
fast and slow periods.
This morning I noticed that the connection slows down while our SMTP mailer is
sending mail to our ISP and then returns to normal as soon as the message is
sent. I have checked the current configuration of our SMTP mailer against the
documented config and nothing appears to have changed. I have restarted to no
avail. Which brings me to ethereal.
I downloaded and installed the Windows version to my laptop and captured all
data while an email message was being sent to our ISP. Filtering to show only
packets from my mail server to my ISPs mail server showed that things start
normally with the usual SMTP hand shaking stuff, then things appear to go a bit
awry. Almost every packet says "TCP Window Full" in the Info column. These
lines are in red text on a black background which makes me thing they're not
good.
I've tried Googling for "TCP Window Full" but without success. Which is why
I've come to the horses mouth. Does anyone know if this is the root cause of
the problem, and if so, what the solution might be?
Yours
Phil
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