anchor.diff:      {method_not_allowed, Methods::binary()} |
       proxy_authenticate | {proxy_authenticate, Realm::binary()} |
       timeout | {timeout, Text::binary()} | 
  +    too_large |
       {unsupported_media_type, Types::binary()} | 
       {unsupported_media_encoding, Types::binary()} |
       unsupported_uri_scheme | 
  
positive.code: %%   <tr><td>`timeout'</td><td>408</td><td></td></tr>
  %%   <tr><td>`{timeout, Text}'</td><td>408</td>
  %%       <td>`Text' will be used in SIP reason line</td></tr>
  %%   <tr><td>`{unsupported_media_type, Types}'</td><td>415</td>
  %%       <td>Generates a new `Accept' header using `Types'</td></tr>
  %%   <tr><td>`{unsupported_media_encoding, Types}'</td><td>415</td>
  
negative.code:         code=415, 
          headers = nksip_headers:new([{single, <<"Accept">>, Types1}])
      };
  reqreply(too_large) ->
      #reqreply{code=413};
  reqreply({unsupported_media_encoding, Types}) ->
      Types1 = nksip_lib:to_binary(Types),    
      #reqreply{
  