anchor.diff:      RC = int(get_avp_value(Dict, 'Result-Code', Rec)),
       PE = is_protocol_error(RC),
   
  -    %% Check that the E bit is set only for 3xxx result codes.
  -    (not (E orelse PE))
  -        orelse (E andalso PE)
  +    %% Check that Result-Code matches E-bit.
  +    (not (E orelse PE))        %% non-3xxx answer without E-bit
  +        orelse (E andalso PE)  %% 3xxx answer with E-bit
           orelse x({invalid_error_bit, RC}, answer, [Dir, Pkt]),
   
       irc(TPid, Hdr, Dir, rc_counter(Dict, Rec, RC)).
  
positive.code: 
  answer(Pkt, SvcName, Dict, App, #request{transport = TPid} = Req) ->
      try
          incr(recv, Pkt, Dict, TPid)
      of
          _ -> answer(Pkt, SvcName, App, Req)
      catch
          exit: {invalid_error_bit, _} = E ->
              answer(Pkt#diameter_packet{errors = [E]}, SvcName, App, Req)
      end.
  
  answer(Pkt,
  
negative.code: incr(TPid, Counter) ->
      diameter_stats:incr(Counter, TPid, 1).
  
  %% rc_counter/2
  
  %% RFC 3588, 7.6:
  %%
  