SOLVED: performance of imap_open (= DNS issue + RSH timeout delay )

Bill McCoy Bill.McCoy at
Wed Apr 23 20:20:31 EDT 2003

Thanks once again for all the ideas. In the event my performance problems
were the result of 2 totally different issues: 

1. A quick Ethereal check pointed out the obvious problem that my remote
WinXP web server was attempting NBNS (aka WINS) and the 4 sec delay
represented the time for its several attempts at this to time out and have
it revert to DNS. Adding the IMAP server name to the WinXP equivalent of
/etc/hosts eliminated this delay.

2. My localhost problem wasn't so clearly traceable via Ethereal, but
building the UW C client library (the basis of PHP's IMAP extension) on my
RedHat server and running the included "mtest" utility pointed out the
problem, which was a 15 sec timeout on an attempted RSH connection (RIMAP)
before the client lib reverts to plain old IMAP. This (I believe recently
changed) behavior is documented for example here: . Adding
"/norsh" after the protocol specification in the imap_open call eliminated
the delay. 

I am pleased to report that after the elimination of these unnecessary
delays Cyrus IMAP is performing at approximately twice the overall speed of
Exchange on the same data. That's more like it! Thanks...

--Bill McCoy

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