On Fri, 14 Sep 2012, Andrew Hume wrote:
because there was literally nothing else to do, the networking folks
worked on the link that was dropping packets and found it was a 4 port
channel with a couple of ports down and utilisation was high. so given
they actually had a guy on site, they had him go and check it
physically. long story short, he was able to replace a couple broken
GBICs and fix a miscabling and voila! the link was now running at 4x the
original speed. and no packet loss!!
and wouldn't you know it, approximately 10s later, no more TCP 0 window
messages and our data streaming started working. and has worked
flawlessly since. so despite the fact that "this minorly defective link
couldn't possibly" cause the problem, it apparently did. (although
no-one could explain the mechanism.)
Thanks for the story Andrew. When training up junior sysadmins I always
encourage them to look deeper if they see 'odd' or 'strange' behaviour on
either a system or the network. Time and time again these odd and strange
behaviours, that initially appear innocuous, turn out to be symptoms of a
more serious existing or potential future problem.
Cheers,
Rob
--
Email: rob...@timetraveller.org Linux counter ID #16440
IRC: Solver (OFTC & Freenode)
Web: http://www.practicalsysadmin.com
Director, Software in the Public Interest (http://spi-inc.org/)
"Information is a gas"
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