anchor.diff:      parse_list('require', Ext, Rest);
   
   process(f, 'require', Ext) ->
  -    sip_binary:any_to_binary(Ext);
  -
  -%% ...
  -process(fn, 'proxy-require', _Ignore) -> <<"Proxy-Require">>;
  -process(p, 'proxy-require', Bin) ->
  -    {ExtBin, Rest} = sip_binary:parse_token(Bin),
  -    Ext = sip_binary:binary_to_existing_atom(sip_binary:to_lower(ExtBin)),
  -    parse_list('proxy-require', Ext, Rest);
  -
  -process(f, 'proxy-require', Ext) ->
       sip_binary:any_to_binary(Ext);
   
   %% ...
  
positive.code:                                 {cnonce, <<"0a4f113b">>}, {opaque, <<"5ccc069c403ebaf9f0171e9517f40e41">>},
                                  {qop, auth}, {nc, 1}, {param, <<"value">>}, {param2, <<"va lue">>}]))),
  
  
  
  
  
negative.code:     % same as Authorization header
      process(f, 'authorization', Auth);
  
  %% 20.29 Proxy-Require
  %% http://tools.ietf.org/html/rfc3261#section-20.29
  process(fn, 'proxy-require', _Ignore) -> <<"Proxy-Require">>;
  process(p, 'proxy-require', Bin) ->
      {ReqBin, Rest} = sip_binary:parse_token(Bin),
      Ext = sip_binary:binary_to_existing_atom(sip_binary:to_lower(ReqBin)),
      parse_list('require', Ext, Rest);
  
  process(f, 'proxy-require', Bin) ->
      sip_binary:any_to_binary(Bin);
  
  %% .....
  process(pn, <<"v">>, _Ignore) -> 'via';
  