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Named Pipes vs TCP - Connection Errors Expand / Collapse
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Posted Thursday, June 20, 2013 4:52 AM
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Hello,

A bit of a strange one....and i swear this is a networking issue somewhere....but according to the networks team they cannot find anything.

Wanted to know if anyone here can think of something to check and why the temporary workaround works!!

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We have a satellite office, connected by a high-speed dedicated link (not VPN) back to our corporate network. In this office are a couple of user PC's which use Crystal Reports to access a SQL database held in the datacentre. They have been experiencing issues with both Crystal Reports and using SSMS, and have been getting the error:

Error Number:121 Error Message:TCP Provider: The semaphore time-out period has expired.

This will happen the second time they run the report or associated select query from SSMS....the first time it always works. If i log off and back on again it will also work....but any subsequent attempt fails.

Through some investigation we found that this is the only occurence of this error so cannot be related to the database server itself. Moving the users PC into the main office (different subnet) resolves the issue. Moving an already working PC from the main office to the satellite office causes the issue to appear on that machine also.

The workaround i found was to change the connection string to use Named Pipes. This allows the query and Crystal Reports to run successfully every time. I know it misses out the network stack (TCP) by using named pipes but for the life of me i cannot figure out exactly why this would work every time if there was a genuine network issue.

All the forums on the internet and here just point people to the Microsoft networking investigation article. I have checked a number of the settings (TCP offload, TCP Chimney etc) and they are all disabled on the SQL Server. They are active on the user desktop though....but then again they are active on my desktop and i experience no issues.

Without something definitive to help me explain to the networks team why the named pipes connection always works and why it is an intermittent issue....they will not help me!

Many thanks
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