internal static void WriteProxyData11(
     this OutputStream ostr,
     string facet,
     InvocationMode invocationMode,
     Protocol protocol,
     Encoding encoding)
 {
     Debug.Assert(ostr.Encoding == Encoding.V11);
     ostr.WriteIce1Facet(facet);
     ostr.Write(invocationMode);
     ostr.WriteBool(false); // "secure"
     ostr.Write(protocol);
     ostr.WriteByte(0);     // protocol minor
     encoding.IceWrite(ostr);
 }