anchor.diff:  		#m2pa_msg{msg_class = ?M2PA_CLASS_M2PA,
   			  msg_type = ?M2PA_TYPE_USER} ->
   			Mtp3 = M2pa#m2pa_msg.mtp3,
  +			LoopDat2 = LoopDat#m2pa_state{last_bsn_received = FsnRecv},
  +			case Mtp3 of
  +				undefined ->
  +					ok;
  +				_ ->
  +					send_userdata_ack(LoopDat2)
  +			end,
   			Prim = osmo_util:make_prim('MTP','TRANSFER',indication, Mtp3),
  -			{ok, Prim, LoopDat#m2pa_state{last_bsn_received = FsnRecv}};
  +			{ok, Prim, LoopDat2};
   		#m2pa_msg{msg_type = ?M2PA_TYPE_LINK} ->
   			handle_linkstate(M2pa, LoopDat),
   			{ignore, LoopDat};
  
positive.code: 	tx_sctp(Stream, M2paBin),
  	LoopDat.
  
  tx_sctp(Stream, Payload) when is_integer(Stream), is_binary(Payload) ->
  	Param = {Stream, ?M2PA_PPID, Payload},
  	% sent to 'ourselves' (behaviour master module)
  
negative.code: 	{ok, Prim, LoopDat}.
  
  
  % sctp_core indicates that we have received some data...
  rx_sctp(#sctp_sndrcvinfo{ppid = ?M2PA_PPID}, Data, State, LoopDat) ->
  	{ok, M2pa} = m2pa_codec:parse_msg(Data),
  	FsnRecv = M2pa#m2pa_msg.fwd_seq_nr,
  