anchor.diff:  process(f, 'content-length', Length) when is_integer(Length) ->
       sip_binary:integer_to_binary(Length);
   
  +%% 20.15 Content-Type
  +%% http://tools.ietf.org/html/rfc3261#section-20.15
  +process(pn, <<"c">>, _Ignore) -> 'content-type';
  +process(fn, 'content-type', _Ignore) -> <<"Content-Type">>;
  +process(p, 'content-type', Bin) ->
  +    {Media, <<>>} = parse_media_range(Bin, fun parse_generic_param/2),
  +    Media;
  +
  +process(f, 'content-type', CType) when is_record(CType, sip_hdr_mediatype) ->
  +    Type = sip_binary:any_to_binary(CType#sip_hdr_mediatype.type),
  +    SubType = sip_binary:any_to_binary(CType#sip_hdr_mediatype.subtype),
  +    append_params(<<Type/binary, ?SLASH, SubType/binary>>, CType#sip_hdr_mediatype.params);
  +
  +%% 20.16 CSeq
  +%% http://tools.ietf.org/html/rfc3261#section-20.16
  +process(fn, 'cseq', _Ignore) -> <<"CSeq">>;
  +process(p, 'cseq', Bin) ->
  +    {SeqBin, Bin2} = sip_binary:parse_token(Bin),
  +    {MethodBin, <<>>} = sip_binary:parse_token(Bin2),
  +    Sequence = sip_binary:binary_to_integer(SeqBin),
  +    Method = sip_binary:binary_to_existing_atom(sip_binary:to_upper(MethodBin)),
  +    cseq(Sequence, Method);
  +
  +process(f, 'cseq', CSeq) when is_record(CSeq, sip_hdr_cseq) ->
  +    SequenceBin = sip_binary:integer_to_binary(CSeq#sip_hdr_cseq.sequence),
  +    MethodBin = sip_binary:any_to_binary(CSeq#sip_hdr_cseq.method),
  +    <<SequenceBin/binary, " ", MethodBin/binary>>;
  +
  +
   
   %% .....
   process(pn, <<"v">>, _Ignore) -> 'via';
  
positive.code:                      "Authorization: Digest username=\"Alice\"\r\nCall-ID: callid\r\n",
                       "Call-Info: <http://www.example.com/alice/photo.jpg>\r\nContact: *\r\n",
                       "Content-Disposition: session\r\nContent-Encoding: gzip\r\n",
                       "Content-Language: en\r\nContent-Length: 5\r\n"
  
                       "Content-Length: 5\r\nVia: SIP/2.0/UDP localhost\r\nFrom: sip:alice@localhost\r\n",
                       "To: sip:bob@localhost\r\n"
  
negative.code:                                    {'authorization', <<"Digest username=\"Alice\"">>}, {'call-id', <<"callid">>},
                                     {'call-info', <<"<http://www.example.com/alice/photo.jpg>">>}, {'contact', <<"*">>},
                                     {'content-disposition', <<"session">>}, {'content-encoding', gzip},
                                     {'content-language', <<"en">>}, {'content-length', <<"5">>},
                                     {'content-type', <<"application/sdp">>},
  
  
                                     {'content-length', <<"5">>}, {'via', <<"SIP/2.0/UDP localhost">>},
                                     {'from', <<"sip:alice@localhost">>}, {'to', <<"sip:bob@localhost">>},
  