MS SQL Server - SQL over VPN

Author

SQL over VPN

dave

2006-11-08, 7:12 pm

Hello,
I'm having a problem using an application which connects to a SQL
server over a VPN (sonicwall).

The app is running very slowly. It takes 5-10 minutes just to open up.
Once it is running is is almost useable but still very slow.

The application connect to a MS SQL server in another office (SBS2000
server running MS SQL).

I have run ethereal to take a look at what is happening when the app is
running and it is saying that lots of the packets (TDS) returning from
the SQL server are malformed.

Has anyone any ideas what I can do to fix this?
The app works fine when on the network local to the server, it's just
over the Sonicwall VPN that causes problems.

I have tried using Named Pipes instead of TCP/IP but it doesn't seem to
help.

thanks,
Dave

sqldba

2006-11-08, 7:12 pm

You may want to ping the SQL Server from your client with the -f and -l
options to see if the packet lenght is set to short some place.

Charles Deaton
www.SQLSIG.org

dave wrote:
> Hello,
> I'm having a problem using an application which connects to a SQL
> server over a VPN (sonicwall).
>
> The app is running very slowly. It takes 5-10 minutes just to open up.
> Once it is running is is almost useable but still very slow.
>
> The application connect to a MS SQL server in another office (SBS2000
> server running MS SQL).
>
> I have run ethereal to take a look at what is happening when the app is
> running and it is saying that lots of the packets (TDS) returning from
> the SQL server are malformed.
>
> Has anyone any ideas what I can do to fix this?
> The app works fine when on the network local to the server, it's just
> over the Sonicwall VPN that causes problems.
>
> I have tried using Named Pipes instead of TCP/IP but it doesn't seem to
> help.
>
> thanks,
> Dave

Sylvain Lafontaine

2006-11-08, 7:12 pm

What kind of application? If you are using a mdb file with linked tables,
don't expect to break any speed record.

Try using the sql-server client tools like EM or QA and, very important, the
Profiler to see if you really have a speed problem because of the VPN and
not because of your application. (In the past, I've seen a MDB file taking
20 minutes to open, so 5-10 minutes is not so bad).

Also, make sure that your VPN is not receiving a lot of bad or unencrypted
packets on a regular basis after the initial connection is made; which would
be something suggesting a bad configuration. I don't know SonicWall but
probably that it can display some useful statistics somewhere.

--
Sylvain Lafontaine, ing.
MVP - Technologies Virtual-PC
E-mail: sylvain aei ca (fill the blanks, no spam please)

"dave" <ihs.test@gmail.com> wrote in message
news:1163007024.757911.93990@b28g2000cwb.googlegroups.com...
> Hello,
> I'm having a problem using an application which connects to a SQL
> server over a VPN (sonicwall).
>
> The app is running very slowly. It takes 5-10 minutes just to open up.
> Once it is running is is almost useable but still very slow.
>
> The application connect to a MS SQL server in another office (SBS2000
> server running MS SQL).
>
> I have run ethereal to take a look at what is happening when the app is
> running and it is saying that lots of the packets (TDS) returning from
> the SQL server are malformed.
>
> Has anyone any ideas what I can do to fix this?
> The app works fine when on the network local to the server, it's just
> over the Sonicwall VPN that causes problems.
>
> I have tried using Named Pipes instead of TCP/IP but it doesn't seem to
> help.
>
> thanks,
> Dave
>

Ryan Sanders

2006-11-08, 7:12 pm

dave wrote:
> Hello,
> I'm having a problem using an application which connects to a SQL
> server over a VPN (sonicwall).
>
> The app is running very slowly. It takes 5-10 minutes just to open up.
> Once it is running is is almost useable but still very slow.
>
> The application connect to a MS SQL server in another office (SBS2000
> server running MS SQL).
>
> I have run ethereal to take a look at what is happening when the app is
> running and it is saying that lots of the packets (TDS) returning from
> the SQL server are malformed.
>
> Has anyone any ideas what I can do to fix this?
> The app works fine when on the network local to the server, it's just
> over the Sonicwall VPN that causes problems.
>
> I have tried using Named Pipes instead of TCP/IP but it doesn't seem to
> help.
>
> thanks,
> Dave
>
>
You may need look in the /diag.html page for something awry. I don't
have access to a SW right now to give you a better answer. Is there
anything helpful in the SW log files?

--

Ryan Sanders
http://ryanlsanders.blogspot.com

dave

2006-11-09, 5:16 am

I've tried the ping test with the -l -f options and can't see anything
wrong.

The client tools work ok for the SQL server over the VPN. Slightly
slower than when on the same LAN but no worse than expected.

I've also looked at the sonicwall packet trace and the log and there is
nothing out of the ordinary in either of them. I tried switching 'allow
Fragmented packets' on the VPN but it didn't change anything.

The only thing that shows a problem is the Ethereal capture which show
lots of 'malformed packet' errors for the TDS packets being returned
from the SQL server.

Surely the app should only be sending a few SQL queries over the
network and so I wouldn't expect it to be particularly slow?

I even tried enabling Path MTU Discovery on my XP machine which causes
TCP to attempt to discover the MTU over the path to the server in case
this was a problem, but it made no difference.

thanks,
Dave

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