anchor.diff:  
   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';
  
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:      ?_assertEqual(70, parse('max-forwards', <<"70">>)),
       ?_assertEqual(<<"70">>, format('max-forwards', 70)),
  
       % Min-Expires
       ?_assertEqual(213, parse('min-expires', <<"213">>)),
       ?_assertEqual(<<"213">>, format('min-expires', 213)),
  
  
  
  