Requests to wcf service are unauthorized

I want to use a wcf service in my asp.net application that uses integrated windows-authentication however all the requests to my Model.svc are 401 Unauthorized. If I change clientCredentialType="Windows" to clientCredentialType="Ntlm" every request is Unauthorized 2 times and the 3rd one is successful.

Here is my web.config:

<configuration>
  <appSettings>
  </appSettings>
  <connectionStrings/>
  <system.web>
    <compilation debug="true" targetFramework="4.0" />
    <authentication mode="Windows" />
  </system.web>
  <!--WCF Configuration-->
  <system.serviceModel>
    <serviceHostingEnvironment multipleSiteBindingsEnabled="true" aspNetCompatibilityEnabled="true"/>
    <bindings>
      <webHttpBinding>
        <binding name="WebHttpBinding_IModel">
          <security mode="TransportCredentialOnly">
            <transport clientCredentialType="Windows" />
          </security>
        </binding>
      </webHttpBinding>
    </bindings>
    <client />
    <services>
      <service behaviorConfiguration="ServiceBehavior" name="Model">
        <endpoint address="" behaviorConfiguration="JsonBehavior" binding="webHttpBinding" bindingConfiguration="WebHttpBinding_IModel" contract="IModel">
          <identity>
            <dns value="localhost" />
          </identity>
        </endpoint>
      </service>
    </services>
    <behaviors>
      <endpointBehaviors>
        <behavior name="JsonBehavior">
          <webHttp />
        </behavior>
      &l开发者_开发知识库t;/endpointBehaviors>
      <serviceBehaviors>
        <behavior name="ServiceBehavior">
          <serviceMetadata httpGetEnabled="true"/>
          <serviceDebug includeExceptionDetailInFaults="true"/>
        </behavior>
     </serviceBehaviors>
    </behaviors>
  </system.serviceModel>
</configuration>

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2 times unauthorized and third working is a part of the protocol. That is the way NTLM authentication works. Is this posing a problem? WCF is made to handle such scenarios, and so your WCF authentication call will work fine.