Wcf – How to impersonate a user to a WCF service

You'll want something like this to increase the message size quotas, in the App.config or Web.config file:

<bindings>
    <basicHttpBinding>
        <binding name="basicHttp" allowCookies="true"
                 maxReceivedMessageSize="20000000" 
                 maxBufferSize="20000000"
                 maxBufferPoolSize="20000000">
            <readerQuotas maxDepth="32" 
                 maxArrayLength="200000000"
                 maxStringContentLength="200000000"/>
        </binding>
    </basicHttpBinding>
</bindings>

And use the binding name in your endpoint configuration e.g.

...
bindingConfiguration="basicHttp"
...

The justification for the values is simple, they are sufficiently large to accommodate most messages. You can tune that number to fit your needs. The low default value is basically there to prevent DOS type attacks. Making it 20000000 would allow for a distributed DOS attack to be effective, the default size of 64k would require a very large number of clients to overpower most servers these days.

In .Net 4.0+, Simplified WCF configuration uses the 'anonymous' configurations when configurations are not explicitly set on a per-services basis in the <services> section. If you remove the name="BasicHttpEndpointBinding" from the <binding> element, or if you duplicate that <binding> element as a new element with no name attribute, it will become the default, anonymous binding that your WCF services will use. This is often useful in cases where you need to serve as well as consume WCF services that may not all have the same config - but at least you can set a default config for the services that do not have a specific config set. The default/anonymous concept is also applicable to <behavior> elements.

<bindings>
  <basicHttpBinding>
    <binding> <!--Notice, no name attribute set-->
      <security mode="TransportCredentialOnly">
        <transport clientCredentialType="Windows" />
      </security>
    </binding>
  </basicHttpBinding>
</bindings>

Also, I might add that if your WCF services require authentication, this means that you will either need to consume the service using a real user account, or you will need to grant the the DOMAIN\CLIENTCOMPUTERNAME$ account access to the service - so, perhaps the proper solution for many people may be to alter the configuration to instead allow anonymous access (which is not discussed in my answer). Still, I do sometimes actually elect to secure my WCF services with Windows (Kerberos) authentication.