anchor.diff:                       "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-Type: application/sdp\r\n",
  +                     "Content-Type: application/sdp\r\nCSeq: 123 INVITE\r\n",
  +                     "Date: Sat, 13 Nov 2010 23:29:00 GMT\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"
  -                     "CSeq: 123 INVITE\r\nMax-Forwards: 70\r\nx-custom-atom: 25\r\nAllow: INVITE, ACK, CANCEL, OPTIONS, BYE\r\n",
  +                     "Max-Forwards: 70\r\nx-custom-atom: 25\r\nAllow: INVITE, ACK, CANCEL, OPTIONS, BYE\r\n",
                        "Supported: 100rel\r\nUnsupported: bar, baz\r\nRequire: foo\r\nProxy-Require: some\r\n",
                        "X-Custom: value\r\n">>,
                      format_headers([{'accept', <<"*/*">>}, {'accept-encoding', <<"identity">>},
  
positive.code:     MethodBin = sip_binary:any_to_binary(CSeq#sip_hdr_cseq.method),
      <<SequenceBin/binary, " ", MethodBin/binary>>;
  
  
  
  %% .....
  process(pn, <<"v">>, _Ignore) -> 'via';
  
negative.code:                                    {'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">>}, {'cseq', <<"123 INVITE">>},
                                     {'date', <<"Sat, 13 Nov 2010 23:29:00 GMT">>},
  
  
                                     {'content-length', <<"5">>}, {'via', <<"SIP/2.0/UDP localhost">>},
                                     {'from', <<"sip:alice@localhost">>}, {'to', <<"sip:bob@localhost">>},
                                     {'max-forwards', 70}, {'x-custom-atom', 25},
                                     {'allow', <<"INVITE, ACK, CANCEL, OPTIONS, BYE">>},
                                     {'supported', <<"100rel">>}, {'unsupported', <<"bar, baz">>},
                                     {'require', <<"foo">>}, {'proxy-require', <<"some">>},
  