anchor.diff:                                     {'date', <<"Sat, 13 Nov 2010 23:29:00 GMT">>}, {'error-info', <<"<sip:not-in-service-recording@atlanta.com>">>},
                                      {'expires', <<"213">>}, {'from', <<"sip:alice@localhost">>},
                                      {'in-reply-to', <<"70710@saturn.bell-tel.com, 17320@saturn.bell-tel.com">>}, {'max-forwards', 70},
  +                                   {'min-expires', <<"213">>},
   
   
                                      {'content-length', <<"5">>}, {'via', <<"SIP/2.0/UDP localhost">>},
  
positive.code:                      "Content-Type: application/sdp\r\nCSeq: 123 INVITE\r\n",
                       "Date: Sat, 13 Nov 2010 23:29:00 GMT\r\nError-Info: <sip:not-in-service-recording@atlanta.com>\r\n",
                       "Expires: 213\r\nFrom: sip:alice@localhost\r\n",
                       "In-Reply-To: 70710@saturn.bell-tel.com, 17320@saturn.bell-tel.com\r\nMax-Forwards: 70\r\n"
  
                       "Content-Length: 5\r\nVia: SIP/2.0/UDP localhost\r\n",
                       "To: sip:bob@localhost\r\n"
  
negative.code: 
  process(f, 'max-forwards', Hops) when is_integer(Hops) ->
      sip_binary:integer_to_binary(Hops);
  
  %% 20.23 Min-Expires
  %% http://tools.ietf.org/html/rfc3261#section-20.23
  process(fn, 'min-expires', _Ignore) -> <<"Min-Expires">>;
  process(p, 'min-expires', Bin) ->
      sip_binary:binary_to_integer(Bin);
  
  process(f, 'min-expires', Length) when is_integer(Length) ->
      sip_binary:integer_to_binary(Length);
  
  
  %% .....
  process(pn, <<"v">>, _Ignore) -> 'via';
  