c# - Initial connection to SQL Server Connection Is Slow. Why?

Question

I have run into a situation with a C# application installed at two sites where the initial connection to SQL Server is extremely slow. I wrote a test application to verify where the slowdown occurs and it is on the first SQLConnection.Open statement. It was taking about 41 seconds to establish a connection to the server via named pipes. We thought it might be a DNS issue but its just as slow using a TCP/IP connection. After the initial connection is made the connection is pooled and the application responds normally. Both the workstation and the server are decent machines running Windows 7 Pro, Core 2 Duo 3.16 Ghz with 4 gig of Ram. I did find the following article on a microsoft forum:

http://social.msdn.microsoft.com/Forums/en/windowscompatibility/thread/f295994c-5812-4e46-8ac9-f05471d4dd54

Turning off the LLMNR protocol did cut the initial connection time in about half to 21 seconds. However, this is still a long time to get an initial connection to SQL Server. The only things slightly different from our norm is that DNS in this case is done thru a router and not an actual server. This has occurred at only two places so far, others run with no issues. Any help would be appreciated.

Thank You, Dennis

Answer 1

In front of the server on the connection string, add np:

This becomes Server=np:serverinstance and forces the Named Pipes instead of the default of TCP.

I could of probably changed the priority to use Named Pipes before TCP... but I did not want to mess with that on the server.