A sysadmin once received a complaint that a university's email
system could not send messages further than 500 miles away.
After much troubleshooting, he discovered that a server upgrade
had shortened the "timeout" value for network connections.
The connection would
drop if the data took more than 3 milliseconds to travel.
This time limit corresponded almost exactly to a 500-mile round
trip, causing distant emails to fail while local ones worked.



