Q:

MustUnderstand attribute in WCF response causes error for Java/Axis client

We have developed a WCF4 service with usernameToken authentication that is being consumed by a Java/Axis client (that we have no control over).
I can see that the body of the request coming in looks like this...
<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/">
  <soapenv:Header>
    <wss:Security xmlns:wss="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
      <wss:UsernameToken>
        <wss:Username>username</wss:Username>
        <wss:Password>password</wss:Password>
      </wss:UsernameToken>
    </wss:Security>
  </soapenv:Header>
  <soapenv:Body>
    {snipped}
  </soapenv:Body>
</soapenv:Envelope>

and the response we are returning looks like this...
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
  <s:Header>
    <o:Security s:mustUnderstand="1" xmlns:o="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-secext-1.0.xsd">
      <u:Timestamp u:Id="_0">
        <u:Created>2012-05-02T01:23:12.711Z</u:Created>
        <u:Expires>2012-05-02T01:28:12.711Z</u:Expires>
      </u:Timestamp>
    </o:Security>
  </s:Header>
  <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
    {snipped}
  </s:Body>
</s:Envelope>

The problem is the s:mustUnderstand="1" attribute in the response. This is causing a "Must Understand check failed" error in the Java/Axis client.
Does anyone know how to configure WCF to remove this s:mustUnderstand attribute or at least set it to "0" instead of "1"?

A:

The solution we came up with to overcome this interop problem was to change to a custom binding and specify the includeTimestamp="false" attribute. By doing this the timestamps (Created and Expired) were not added into the response and therefore the whole security header dissapeared - including the mustUnderstand attribute which was causing all the problems.
<customBinding>
    <binding name="customBindingConfig">
        <security authenticationMode="UserNameOverTransport" includeTimestamp="false" />
         <textMessageEncoding messageVersion="Soap11" />
         <httpTransport />
   </binding>
</customBinding>

So the response now simply looks like this...
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/" xmlns:u="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
    <s:Body xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
        {snipped}
    </s:Body>
</s:Envelope>

