Securing my webservice with Windows authentication

[alberich]

I have a problem securing my webservice with Windows authentication.
The goal is a client app transfering (large amounts of) data to a
server which is blocked for anonymous requests.
To do this, the client app asks the user for credentials, build some
NetworkCredenti al wit them & adds them to the CredentialCache .
When i look at the iis log, each call to my webmethod appears twice in
the log - first try without credentials (which fails with http 401) and
then a second one with credentials (which works).
As far as i see also the data is transmitted two times, really bad.
My question: How can the (first) anonymous request be suppressed?

To make it clear, here is some code:

Simple client console app, calling the server method ten times:
******** Client app:
WSTest.SecureWS myWS = new WSTest.SecureWS (); // Webservice proxy
// Credentials:
CredentialCache credCache = new CredentialCache ();
NetworkCredenti al netCred = new NetworkCredenti al("peter", <password>);
credCache.Add( new Uri(myWS.Url), "NTLM", netCred );
myWS.Credential s = credCache;
// webservice calls:
int startCount=Envi ronment.TickCou nt;
for (int i=0; i<10; i++) {
Console.WriteLi ne(myWS.WhoAmI( "".PadLeft(1000 0,"x"[0])));
}

int endCount = Environment.Tic kCount;
Console.WriteLi ne("this takes " + (endCount-startCount).ToS tring() +
"ms");
******** /Client app

Simple server webmethod:
******** Server method:
[WebMethod]
public string WhoAmI(string postData) {
return "You are: [" + Thread.CurrentP rincipal.Identi ty.Name +
"] - " + postData.Length + " bytes received.";
}

******** /Server method

With server configuration like this
<authenticati on mode="Windows" />
<deny users="?" />
the iis log shows
******** log
2005-09-19 13:33:36 127.0.0.1 - 127.0.0.1 80 POST /WSTest/SecureWS.asmx
- 401 2241 10588 0 ...
2005-09-19 13:33:36 127.0.0.1 peter 127.0.0.1 80 POST
/WSTest/SecureWS.asmx - 200 727 10834 0 ...
******** /log
for each method call. If no authorization is requested (<allow
users="*" />), the iis log shows
******** log
2005-09-19 13:33:52 127.0.0.1 - 127.0.0.1 80 POST /WSTest/SecureWS.asmx
- 200 712 10588 0 ...
******** /log
for each method call.

thx
alberich