diff --git a/src/m2pa_codec.erl b/src/m2pa_codec.erl
new file mode 100644
index 0000000..585b9c9
--- /dev/null
+++ b/src/m2pa_codec.erl
@@ -0,0 +1,66 @@
+% RFC 4165 MTP2 P2P Adaption Layer coding / decoding
+
+% (C) 2012 by Harald Welte <laforge@gnumonks.org>
+%
+% All Rights Reserved
+%
+% This program is free software; you can redistribute it and/or modify
+% it under the terms of the GNU Affero General Public License as
+% published by the Free Software Foundation; either version 3 of the
+% License, or (at your option) any later version.
+%
+% This program is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU Affero General Public License
+% along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+-module(m2pa_codec).
+-author('Harald Welte <laforge@gnumonks.org>').
+-include("m2pa.hrl").
+-include("mtp3.hrl").
+
+-export([parse_msg/1, encode_msg/1]).
+
+-compile({parse_transform, exprecs}).
+-export_records([m2pa_msg]).
+
+parse_m2pa_msgt(?M2PA_CLASS_M2PA, ?M2PA_TYPE_LINK, Len, Remain) ->
+	<<State:32/big, Filler/binary>> = Remain,
+	Ret = [{link_state, State}],
+	if
+		byte_size(Filler) > 0 ->
+			{undefined, [{filler, Filler}|Ret]};
+		true ->
+			{undefined, Ret}
+	end;
+parse_m2pa_msgt(?M2PA_CLASS_M2PA, ?M2PA_TYPE_USER, Len, RemainIn) ->
+	<<Pri:1, _:7, SIO:8, SIF/binary>> = RemainIn,
+	Mtp3 = #mtp3_msg{service_ind = SIO, m3ua_mp = Pri, payload = SIF},
+	{Mtp3, []}.
+
+parse_msg(DataBin) when is_binary(DataBin) ->
+	<<1:8, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, AllRemain/binary>> = DataBin,
+	<<_:8, BSN:24/big, _:8, FSN:24/big, Remain/binary>> = AllRemain,
+	{Mtp3, Params} = parse_m2pa_msgt(MsgClass, MsgType, MsgLen, Remain),
+	{ok, #m2pa_msg{msg_class = MsgClass, msg_type = MsgType,
+			fwd_seq_nr = FSN, back_seq_nr = BSN,
+			mtp3 = Mtp3, parameters = Params}}.
+
+encode_m2pa_msgt(?M2PA_CLASS_M2PA, ?M2PA_TYPE_USER, Mtp3, _Params) ->
+	<<Mtp3/binary>>;
+encode_m2pa_msgt(?M2PA_CLASS_M2PA, ?M2PA_TYPE_LINK, _, Params) ->
+	State = proplists:get_value(link_state, Params),
+	% FIXME: filler
+	Filler = <<>>,
+	<<State:32/big, Filler/binary>>.
+
+
+encode_msg(Msg) when is_record(Msg, m2pa_msg) ->
+	#m2pa_msg{msg_class = MsgClass, msg_type = MsgType, fwd_seq_nr = FSN,
+			back_seq_nr = BSN, mtp3 = Mtp3, parameters = Params} = Msg,
+	Payload = encode_m2pa_msgt(MsgClass, MsgType, Mtp3, Params),
+	MsgLen = byte_size(Payload) + 16,
+	<<1:8, 0:8, MsgClass:8, MsgType:8, MsgLen:32/big, 0:8, BSN:24/big, 0:8, FSN:24/big, Payload/binary>>.