Windows authentication in SharePoint Web Services

There is a SharePoint Foundation 2010 environment on the server. The server is using windows authentication.

There are many web services there. One e.g.: http://server/_vti_bin/Webs.asmx

However... I would like to call those web services from other site/client. How would I be able to call the web service and authenticate too.

The following call results in 401 UNAUTHORIZED response:

<?xml version="1.0" encoding="utf-8"?>
<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
  <soap:Body>
    <GetWeb xmlns="http://schemas.microsoft.com/sharepoint/soap/">
      <webUrl>http://server/testsite/default.aspx</webUrl>
    </GetWeb>
  </soap:Body>
</soap:Envelope>

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