Merge branch 'maint'

19 files changed, 1717 insertions, 1134 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 2cbe48ecce..3ad24257a5 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -798,6 +798,35 @@ be matched by corresponding &capability; configuration, of
 </item>
 
 <tag>
+<marker id="decode_format"/>
+<c>{decode_format, record | list | map | false}</c></tag>
+<item>
+<p>
+The format of decoded messages and grouped AVPs in the <c>msg</c> field
+of diameter_packet records and <c>value</c> field of diameter_avp
+records respectively.
+If <c>record</c> then a record whose definition is generated from the
+dictionary file in question.
+If <c>list</c> or <c>map</c> then a <c>[Name | Avps]</c> pair where
+<c>Avps</c> is either a list of AVP name/values pairs or a map keyed on
+AVP names respectively.
+If <c>false</c> then the representation is omitted and <c>msg</c> and
+<c>value</c> fields are set to <c>false</c>.
+See also &codec_message;.</p>
+
+<p>
+Defaults to <c>record</c>.</p>
+
+<note>
+<p>
+AVPs are decoded into a list of diameter_avp records in <c>avps</c>
+field of diameter_packet records independently of
+<c>decode_format</c>.</p>
+</note>
+
+</item>
+
+<tag>
 <marker id="incoming_maxlen"/><c>{incoming_maxlen, 0..16777215}</c></tag>
 <item>
 <p>
@@ -927,6 +956,37 @@ Defaults to the empty list.</p>
 </item>
 
 <tag>
+<marker id="strict_arities"/><c>{strict_arities, boolean()
+                                               | encode
+                                               | decode}</c></tag>
+<item>
+<p>
+Whether or not to require that the number of AVPs in a message or
+grouped AVP agree with those specified in the dictionary in question.
+If <c>true</c> then mismatches in an outgoing messages cause message
+encoding to fail, while mismatches in an incoming message are reported
+as 5005/5009 errors in the errors field of the diameter_packet record
+passed to &app_handle_request; or &app_handle_answer; callbacks.
+If <c>false</c> then neither error is enforced/detected.
+If <c>encode</c> or <c>decode</c> then errors are only
+enforced/detected on outgoing or incoming messages respectively.</p>
+
+<p>
+Defaults to <c>true</c>.</p>
+
+<note>
+<p>
+Disabling arity checks affects the form of messages at encode/decode.
+In particular, decoded AVPs are represented as lists of values,
+regardless of the AVP's arity (ie. expected number in the message/AVP
+grammar in question), and values are expected to be supplied as lists
+at encode.
+This differs from the historic decode behaviour of representing AVPs
+of arity 1 as bare values, not wrapped in a list.</p>
+</note>
+</item>
+
+<tag>
 <marker id="strict_mbit"/><c>{strict_mbit, boolean()}</c></tag>
 <item>
 <p>
@@ -993,6 +1053,26 @@ The default value is for backwards compatibility.</p>
 
 </item>
 
+<tag>
+<marker id="traffic_counters"/><c>{traffic_counters, boolean()}</c></tag>
+<item>
+<p>
+Whether or not to count application-specific messages; those for which
+&man_app; callbacks take place.
+If false then only messages handled by diameter itself are counted:
+CER/CEA, DWR/DWA, DPR/DPA.</p>
+
+<p>
+Defaults to <c>true</c>.</p>
+
+<note>
+<p>
+Disabling counters is a performance improvement, but means that the
+omitted counters are not returned by &service_info;.</p>
+</note>
+
+</item>
+
 <tag><c>{use_shared_peers, boolean() | [node()] | evaluable()}</c></tag>
 <item>
 <p>
diff --git a/lib/diameter/doc/src/diameter_codec.xml b/lib/diameter/doc/src/diameter_codec.xml
index 0117c1c88a..0846334d23 100644
--- a/lib/diameter/doc/src/diameter_codec.xml
+++ b/lib/diameter/doc/src/diameter_codec.xml
@@ -230,7 +230,8 @@ header.</p>
 </item>
 
 <tag>
-<marker id="message"/><c>message() = record() | list()</c></tag>
+<marker id="message"/><c>message() = record()
+                                   | maybe_improper_list()</c></tag>
 <item>
 <p>
 The representation of a Diameter message as passed to
@@ -240,7 +241,11 @@ a message as defined in a dictionary file is encoded as a record with
 one field for each component AVP.
 Equivalently, a message can also be encoded as a list whose head is
 the atom-valued message name (as specified in the relevant dictionary
-file) and whose tail is a list of <c>{AvpName, AvpValue}</c> pairs.</p>
+file) and whose tail is either a list of AVP name/values
+pairs or a map with values keyed on AVP names.
+The format at decode is determined by &mod_service_opt;
+<c>decode_format</c>.
+Any of the formats is accepted at encode.</p>
 
 <p>
 Another list-valued representation allows a message to be specified
diff --git a/lib/diameter/include/diameter_gen.hrl b/lib/diameter/include/diameter_gen.hrl
index fb6370fe54..548763ec7d 100644
--- a/lib/diameter/include/diameter_gen.hrl
+++ b/lib/diameter/include/diameter_gen.hrl
@@ -26,13 +26,13 @@
 
 %% encode_avps/3
 
-encode_avps(Name, Vals, Opts) ->
-    diameter_gen:encode_avps(Name, Vals, Opts#{module => ?MODULE}).
+encode_avps(Name, Avps, Opts) ->
+    diameter_gen:encode_avps(Name, Avps, Opts#{module => ?MODULE}).
 
 %% decode_avps/2
 
-decode_avps(Name, Recs, Opts) ->
-    diameter_gen:decode_avps(Name, Recs, Opts#{module => ?MODULE}).
+decode_avps(Name, Avps, Opts) ->
+    diameter_gen:decode_avps(Name, Avps, Opts#{module => ?MODULE}).
 
 %% avp/5
 
diff --git a/lib/diameter/src/base/diameter.erl b/lib/diameter/src/base/diameter.erl
index bd92e16fba..2e18a1d903 100644
--- a/lib/diameter/src/base/diameter.erl
+++ b/lib/diameter/src/base/diameter.erl
@@ -47,6 +47,8 @@
          stop/0]).
 
 -export_type([evaluable/0,
+              decode_format/0,
+              strict_arities/0,
               restriction/0,
               message_length/0,
               remotes/0,
@@ -330,6 +332,18 @@ call(SvcName, App, Message) ->
 -type message_length()
    :: 0..16#FFFFFF.
 
+-type decode_format()
+   :: record
+    | list
+    | map
+    | false
+    | record_from_map.
+
+-type strict_arities()
+   :: false
+    | encode
+    | decode.
+
 %% Options passed to start_service/2
 
 -type service_opt()
@@ -338,7 +352,10 @@ call(SvcName, App, Message) ->
     | {restrict_connections, restriction()}
     | {sequence, sequence() | evaluable()}
     | {share_peers, remotes()}
+    | {decode_format, decode_format()}
+    | {traffic_counters, boolean()}
     | {string_decode, boolean()}
+    | {strict_arities, true | strict_arities()}
     | {strict_mbit, boolean()}
     | {incoming_maxlen, message_length()}
     | {use_shared_peers, remotes()}
diff --git a/lib/diameter/src/base/diameter_codec.erl b/lib/diameter/src/base/diameter_codec.erl
index 82fa796e69..63e39b12d1 100644
--- a/lib/diameter/src/base/diameter_codec.erl
+++ b/lib/diameter/src/base/diameter_codec.erl
@@ -29,7 +29,7 @@
          msg_name/2,
          msg_id/1]).
 
-%% Towards generated encoders (from diameter_gen.hrl).
+%% towards diameter_gen
 -export([pack_data/2,
          pack_avp/2]).
 
@@ -110,7 +110,7 @@ encode(Mod, Opts, Msg) ->
 
 enc(_, Opts, #diameter_packet{msg = [#diameter_header{} = Hdr | As]}
              = Pkt) ->
-    try encode_avps(reorder(As), Opts) of
+    try encode_avps(As, Opts) of
         Avps ->
             Bin = list_to_binary(Avps),
             Len = 20 + size(Bin),
@@ -206,51 +206,12 @@ values(Avps) ->
 
 %% Message as a list of #diameter_avp{} ...
 encode_avps(_, _, [#diameter_avp{} | _] = Avps, Opts) ->
-    encode_avps(reorder(Avps), Opts);
+    encode_avps(Avps, Opts);
 
 %% ... or as a tuple list or record.
 encode_avps(Mod, MsgName, Values, Opts) ->
     Mod:encode_avps(MsgName, Values, Opts).
 
-%% reorder/1
-%%
-%% Reorder AVPs for the relay case using the index field of
-%% diameter_avp records. Decode populates this field in collect_avps
-%% and presents AVPs in reverse order. A relay then sends the reversed
-%% list with a Route-Record AVP prepended. The goal here is just to do
-%% lists:reverse/1 in Grouped AVPs and the outer list, but only in the
-%% case there are indexed AVPs at all, so as not to reverse lists that
-%% have been explicilty sent (unindexed, in the desired order) as a
-%% diameter_avp list. The effect is the same as lists:keysort/2, but
-%% only on the cases we expect, not a general sort.
-
-reorder(Avps) ->
-    case reorder(Avps, []) of
-        false ->
-            Avps;
-        Sorted ->
-            Sorted
-    end.
-
-%% reorder/3
-
-%% In case someone has reversed the list already. (Not likely.)
-reorder([#diameter_avp{index = 0} | _] = Avps, Acc) ->
-    Avps ++ Acc;
-
-%% Assume indexed AVPs are in reverse order.
-reorder([#diameter_avp{index = N} = A | Avps], Acc)
-  when is_integer(N) ->
-    lists:reverse(Avps, [A | Acc]);
-
-%% An unindexed AVP.
-reorder([H | T], Acc) ->
-    reorder(T, [H | Acc]);
-
-%% No indexed members.
-reorder([], _) ->
-    false.
-
 %% encode_avps/2
 
 encode_avps(Avps, Opts) ->
@@ -287,7 +248,8 @@ rec2msg(Mod, Rec) ->
 %% longer *the* decode.
 
 decode(Mod, Pkt) ->
-    Opts = #{string_decode => true,
+    Opts = #{decode_format => record,
+             string_decode => true,
              strict_mbit => true,
              rfc => 6733},
     decode(Mod, Opts, Pkt).
@@ -326,13 +288,7 @@ decode(Mod, AppMod, Opts, Pkt) ->
 %% Relay application: just extract the avp's without any decoding of
 %% their data since we don't know the application in question.
 decode(?APP_ID_RELAY, _, _, _, #diameter_packet{} = Pkt) ->
-    case collect_avps(Pkt) of
-        {E, As} ->
-            Pkt#diameter_packet{avps = As,
-                                errors = [E]};
-        As ->
-            Pkt#diameter_packet{avps = As}
-    end;
+    collect_avps(Pkt);
 
 %% Otherwise decode using the dictionary.
 decode(_, Mod, AppMod, Opts, #diameter_packet{header = Hdr} = Pkt) ->
@@ -341,44 +297,50 @@ decode(_, Mod, AppMod, Opts, #diameter_packet{header = Hdr} = Pkt) ->
                      is_error = IsError}
         = Hdr,
 
-    MsgName = if IsError andalso not IsRequest ->
+    MsgName = if IsError, not IsRequest ->
                       'answer-message';
                  true ->
                       Mod:msg_name(CmdCode, IsRequest)
               end,
 
-    decode_avps(MsgName, Mod, AppMod, Opts, Pkt, collect_avps(Pkt));
+    decode_avps(MsgName, Mod, AppMod, Opts, Pkt);
 
 decode(Id, Mod, AppMod, Opts, Bin)
   when is_binary(Bin) ->
     decode(Id, Mod, AppMod, Opts, #diameter_packet{header = decode_header(Bin),
                                                    bin = Bin}).
 
-%% decode_avps/6
-
-decode_avps(MsgName, Mod, AppMod, Opts, Pkt, {E, Avps}) ->
-    ?LOG(invalid_avp_length, Pkt#diameter_packet.header),
-    #diameter_packet{errors = Failed}
-        = P
-        = decode_avps(MsgName, Mod, AppMod, Opts, Pkt, Avps),
-    P#diameter_packet{errors = [E | Failed]};
+%% decode_avps/5
 
-decode_avps('', _, _, _, Pkt, Avps) ->  %% unknown message ...
-    ?LOG(unknown_message, Pkt#diameter_packet.header),
-    Pkt#diameter_packet{avps = lists:reverse(Avps),
-                        errors = [3001]};   %% DIAMETER_COMMAND_UNSUPPORTED
+decode_avps('', _, _, _, #diameter_packet{header = H,  %% unknown message
+                                          bin = Bin}
+                         = Pkt) ->
+    ?LOG(unknown_message, H),
+    Pkt#diameter_packet{avps = collect_avps(Bin),
+                        errors = [3001]}; %% DIAMETER_COMMAND_UNSUPPORTED
 %% msg = undefined identifies this case.
 
-decode_avps(MsgName, Mod, AppMod, Opts, Pkt, Avps) ->  %% ... or not
+decode_avps(MsgName, Mod, AppMod, Opts, #diameter_packet{bin = Bin} = Pkt) ->
+    {_, Avps} = split_binary(Bin, 20),
     {Rec, As, Errors} = Mod:decode_avps(MsgName,
                                         Avps,
                                         Opts#{dictionary => AppMod,
                                               failed_avp => false}),
     ?LOGC([] /= Errors, decode_errors, Pkt#diameter_packet.header),
-    Pkt#diameter_packet{msg = Rec,
+    Pkt#diameter_packet{msg = reformat(MsgName, Rec, Opts),
                         errors = Errors,
                         avps = As}.
 
+%% reformat/3
+
+reformat(MsgName, Avps, #{decode_format := T})
+  when T == map;
+       T == list ->
+    [MsgName | Avps];
+
+reformat(_, Msg, _) ->
+    Msg.
+
 %%% ---------------------------------------------------------------------------
 %%% # decode_header/1
 %%% ---------------------------------------------------------------------------
@@ -515,24 +477,21 @@ msg_id(<<_:32, Rbit:1, _:7, CmdCode:24, ApplId:32, _/binary>>) ->
 %%% # collect_avps/1
 %%% ---------------------------------------------------------------------------
 
-%% Note that the returned list of AVP's is reversed relative to their
-%% order in the binary. Note also that grouped avp's aren't unraveled,
-%% only those at the top level.
+%% This is only used for the relay decode. Note that grouped avp's
+%% aren't unraveled, only those at the top level.
 
--spec collect_avps(#diameter_packet{} | binary())
-   -> [Avp]
-    | {Error, [Avp]}
- when Avp   :: #diameter_avp{},
-      Error :: {5014, #diameter_avp{}}.
+-spec collect_avps(#diameter_packet{})
+   -> #diameter_packet{};
+                  (binary())
+   -> [#diameter_avp{}].
 
-collect_avps(#diameter_packet{bin = <<_:20/binary, Avps/binary>>}) ->
-    collect_avps(Avps, 0, []);
+collect_avps(#diameter_packet{bin = Bin} = Pkt) ->
+    Pkt#diameter_packet{avps = collect_avps(Bin)};
 
-collect_avps(Bin)
-  when is_binary(Bin) ->
-    collect_avps(Bin, 0, []).
+collect_avps(<<_:20/binary, Avps/binary>>) ->
+    collect(Avps).
 
-%% collect_avps/3
+%% collect/1
 
 %%     0                   1                   2                   3
 %%     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@@ -546,66 +505,48 @@ collect_avps(Bin)
 %%    |    Data ...
 %%    +-+-+-+-+-+-+-+-+
 
-collect_avps(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>,
-             N,
-             Acc) ->
-    collect_avps(Code,
-                 if 1 == V -> I; 0 == V -> undefined end,
-                 1 == M,
-                 1 == P,
-                 Len - 8 - V*4,  %% Might be negative, which ensures
-                 ?PAD(Len),      %%   failure of the Data match below.
-                 Rest,
-                 N,
-                 Acc);
-
-collect_avps(<<>>, _, Acc) ->
-    Acc;
+collect(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>) ->
+    collect(Rest,
+            Code,
+            if 1 == V -> I; 0 == V -> undefined end,
+            Len - 8 - V*4,  %% Might be negative, which ensures
+            ?PAD(Len),      %%   failure of the match below.
+            1 == M,
+            1 == P);
+
+collect(<<>>) ->
+    [];
 
 %% Header is truncated. pack_avp/1 will pad this at encode if sent in
 %% a Failed-AVP.
-collect_avps(Bin, _, Acc) ->
-    {{5014, #diameter_avp{data = Bin}}, Acc}.
+collect(Bin) ->
+    [#diameter_avp{data = {5014, Bin}}].
 
-%% collect_avps/9
+%% collect/7
 
-%% Duplicate the diameter_avp creation in each branch below to avoid
-%% modifying the record, which profiling has shown to be a relatively
-%% costly part of building the list.
-
-collect_avps(Code, VendorId, M, P, Len, Pad, Rest, N, Acc) ->
-    case Rest of
-        <<Data:Len/binary, _:Pad/binary, T/binary>> ->
+collect(Bin, Code, Vid, DataLen, Pad, M, P) ->
+    case Bin of
+        <<Data:DataLen/binary, _:Pad/binary, Rest/binary>> ->
             Avp = #diameter_avp{code = Code,
-                                vendor_id = VendorId,
+                                vendor_id = Vid,
                                 is_mandatory = M,
                                 need_encryption = P,
-                                data = Data,
-                                index = N},
-            collect_avps(T, N+1, [Avp | Acc]);
+                                data = Data},
+            [Avp | collect(Rest)];
         _ ->
             %% Length in header points past the end of the message, or
-            %% doesn't span the header. As stated in the 6733 text
-            %% above, it's sufficient to return a zero-filled minimal
-            %% payload if this is a request. Do this (in cases that we
-            %% know the type) by inducing a decode failure and letting
-            %% the dictionary's decode (in diameter_gen) deal with it.
-            %%
-            %% Note that the extra bit can only occur in the trailing
-            %% AVP of a message or Grouped AVP, since a faulty AVP
-            %% Length is otherwise indistinguishable from a correct
-            %% one here, as we don't know the types of the AVPs being
-            %% extracted.
-            Avp = #diameter_avp{code = Code,
-                                vendor_id = VendorId,
-                                is_mandatory = M,
-                                need_encryption = P,
-                                data = {5014, Rest},
-                                index = N},
-            [Avp | Acc]
+            %% doesn't span the header. Note that an length error can
+            %% only occur in the trailing AVP of a message or Grouped
+            %% AVP, since a faulty AVP Length is otherwise
+            %% indistinguishable from a correct one here, as we don't
+            %% know the types of the AVPs being extracted.
+            [#diameter_avp{code = Code,
+                           vendor_id = Vid,
+                           is_mandatory = M,
+                           need_encryption = P,
+                           data = {5014, Bin}}]
     end.
 
-
 %% 3588:
 %%
 %%   DIAMETER_INVALID_AVP_LENGTH        5014
diff --git a/lib/diameter/src/base/diameter_config.erl b/lib/diameter/src/base/diameter_config.erl
index 34018ae6d3..f1b6e56782 100644
--- a/lib/diameter/src/base/diameter_config.erl
+++ b/lib/diameter/src/base/diameter_config.erl
@@ -712,7 +712,10 @@ make_config(SvcName, Opts) ->
                          {?NOMASK, sequence},
                          {nodes, restrict_connections},
                          {16#FFFFFF, incoming_maxlen},
+                         {true, strict_arities},
                          {true, strict_mbit},
+                         {record, decode_format},
+                         {true, traffic_counters},
                          {true, string_decode},
                          {[], spawn_opt}]),
 
@@ -755,17 +758,34 @@ opt(K, false = B)
        K == use_shared_peers;
        K == monitor;
        K == restrict_connections;
+       K == strict_arities;
        K == strict_mbit;
+       K == decode_format;
+       K == traffic_counters;
        K == string_decode ->
     B;
 
 opt(K, true = B)
   when K == share_peers;
        K == use_shared_peers;
+       K == strict_arities;
        K == strict_mbit;
+       K == traffic_counters;
        K == string_decode ->
     B;
 
+opt(decode_format, T)
+  when T == record;
+       T == list;
+       T == map;
+       T == record_from_map ->
+    T;
+
+opt(strict_arities, T)
+  when T == encode;
+       T == decode ->
+    T;
+
 opt(restrict_connections, T)
   when T == node;
        T == nodes ->
diff --git a/lib/diameter/src/base/diameter_gen.erl b/lib/diameter/src/base/diameter_gen.erl
index e832832876..7a1a46ec52 100644
--- a/lib/diameter/src/base/diameter_gen.erl
+++ b/lib/diameter/src/base/diameter_gen.erl
@@ -26,6 +26,14 @@
 
 -module(diameter_gen).
 
+-compile({inline, [incr/8,
+                   incr/4,
+                   field/1,
+                   setopts/4,
+                   avp_arity/5,
+                   set_failed/2,
+                   set_strict/3]}).
+
 -export([encode_avps/3,
          decode_avps/3,
          grouped_avp/4,
@@ -46,17 +54,23 @@
 -type grouped_avp() :: nonempty_improper_list(#diameter_avp{}, [avp()]).
 -type avp() :: non_grouped_avp() | grouped_avp().
 
+%% The arbitrary arity returned from dictionary avp_arity functions.
+-define(ANY, {0, '*'}).
+
 %% ---------------------------------------------------------------------------
 %% # encode_avps/3
 %% ---------------------------------------------------------------------------
 
--spec encode_avps(parent_name(), parent_record() | avp_values(), map())
+-spec encode_avps(parent_name(),
+                  parent_record() | avp_values() | map(),
+                  map())
    -> iolist()
     | no_return().
 
 encode_avps(Name, Vals, #{module := Mod} = Opts) ->
+    Strict = mget(strict_arities, Opts, encode),
     try
-        encode(Name, Vals, Opts, Mod)
+        encode(Name, Vals, Opts, Strict, Mod)
     catch
         throw: {?MODULE, Reason} ->
             diameter_lib:log({encode, error},
@@ -73,64 +87,109 @@ encode_avps(Name, Vals, #{module := Mod} = Opts) ->
             erlang:error({encode_failure, Reason, Name, Stack})
     end.
 
-%% encode/4
+%% encode/5
 
-encode(Name, Vals, #{ordered_encode := false} = Opts, Mod)
+encode(Name, Vals, Opts, Strict, Mod)
   when is_list(Vals) ->
-    lists:map(fun({F,V}) -> encode(Name, F, V, Opts, Mod) end, Vals);
+    case Opts of
+        #{ordered_encode := false} ->
+            lists:map(fun({F,V}) -> encode(Name, F, V, Opts, Strict, Mod) end,
+                      Vals);
+        _ ->
+            Rec = Mod:'#set-'(Vals, newrec(Mod, Name)),
+            encode(Name, Rec, Opts, Strict, Mod)
+    end;
 
-encode(Name, Vals, Opts, Mod)
-  when is_list(Vals) ->
-    encode(Name, Mod:'#set-'(Vals, newrec(Mod, Name)), Opts, Mod);
+encode(Name, Map, Opts, Strict, Mod)
+  when is_map(Map) ->
+    [enc(Name, F, A, V, Opts, Strict, Mod) || {F,A} <- Mod:avp_arity(Name),
+                                              V <- [mget(F, Map, undefined)]];
 
-encode(Name, Rec, Opts, Mod) ->
-    [encode(Name, F, V, Opts, Mod) || {F,V} <- Mod:'#get-'(Rec)].
+encode(Name, Rec, Opts, Strict, Mod) ->
+    [encode(Name, F, V, Opts, Strict, Mod) || {F,V} <- Mod:'#get-'(Rec)].
 
-%% encode/5
+%% encode/6
+
+encode(Name, AvpName, Values, Opts, Strict, Mod)
+  when Strict /= encode ->
+    enc(Name, AvpName, ?ANY, Values, Opts, Strict, Mod);
 
-encode(Name, AvpName, Values, Opts, Mod) ->
-    enc(Name, AvpName, Mod:avp_arity(Name, AvpName), Values, Opts, Mod).
+encode(Name, AvpName, Values, Opts, Strict, Mod) ->
+    Arity = Mod:avp_arity(Name, AvpName),
+    enc(Name, AvpName, Arity, Values, Opts, Strict, Mod).
 
-%% enc/6
+%% enc/7
 
-enc(_, AvpName, 1, undefined, _, _) ->
+enc(Name, AvpName, Arity, Values, Opts, Strict, Mod)
+  when Strict /= encode, Arity /= ?ANY ->
+    enc(Name, AvpName, ?ANY, Values, Opts, Strict, Mod);
+
+enc(_, AvpName, 1, undefined, _, _, _) ->
     ?THROW([mandatory_avp_missing, AvpName]);
 
-enc(Name, AvpName, 1, Value, Opts, Mod) ->
-    enc(Name, AvpName, [Value], Opts, Mod);
+enc(Name, AvpName, 1, Value, Opts, _, Mod) ->
+    H = avp_header(AvpName, Mod),
+    enc1(Name, AvpName, H, Value, Opts, Mod);
+
+enc(_, _, {0,_}, [], _, _, _) ->
+    [];
 
-enc(_, _, {0,_}, [], _, _) ->
+enc(_, _, _, undefined, _, _, _) ->
     [];
 
-enc(_, AvpName, _, T, _, _)
-  when not is_list(T) ->
-    ?THROW([repeated_avp_as_non_list, AvpName, T]);
+%% Be forgiving when a list of values is expected. If the value itself
+%% is a list then the user has to wrap it to avoid each member from
+%% being interpreted as an individual AVP value.
+enc(Name, AvpName, Arity, V, Opts, Strict, Mod)
+  when not is_list(V) ->
+    enc(Name, AvpName, Arity, [V], Opts, Strict, Mod);
 
-enc(_, AvpName, {Min, _}, L, _, _)
-  when length(L) < Min ->
-    ?THROW([repeated_avp_insufficient_arity, AvpName, Min, L]);
+enc(Name, AvpName, {Min, Max}, Values, Opts, Strict, Mod) ->
+    H = avp_header(AvpName, Mod),
+    enc(Name, AvpName, H, Min, 0, Max, Values, Opts, Strict, Mod).
 
-enc(_, AvpName, {_, Max}, L, _, _)
-  when Max < length(L) ->
-    ?THROW([repeated_avp_excessive_arity, AvpName, Max, L]);
+%% enc/10
 
-enc(Name, AvpName, _, Values, Opts, Mod) ->
-    enc(Name, AvpName, Values, Opts, Mod).
+enc(Name, AvpName, H, Min, N, Max, Vs, Opts, Strict, Mod)
+  when Strict /= encode;
+       Max == '*', Min =< N ->
+    [enc1(Name, AvpName, H, V, Opts, Mod) || V <- Vs];
 
-%% enc/5
+enc(_, AvpName, _, Min, N, _, [], _, _, _)
+  when N < Min ->
+    ?THROW([repeated_avp_insufficient_arity, AvpName, Min, N]);
 
-enc(Name, 'AVP', Values, Opts, Mod) ->
-    [enc_AVP(Name, A, Opts, Mod) || A <- Values];
+enc(_, _, _, _, _, _, [], _, _, _) ->
+    [];
 
-enc(_, AvpName, Values, Opts, Mod) ->
-    enc(AvpName, Values, Opts, Mod).
+enc(_, AvpName, _, _, N, Max, _, _, _, _)
+  when Max =< N ->
+    ?THROW([repeated_avp_excessive_arity, AvpName, Max]);
 
-%% enc/4
+enc(Name, AvpName, H, Min, N, Max, [V|Vs], Opts, Strict, Mod) ->
+    [enc1(Name, AvpName, H, V, Opts, Mod)
+     | enc(Name, AvpName, H, Min, N+1, Max, Vs, Opts, Strict, Mod)].
 
-enc(AvpName, Values, Opts, Mod) ->
-    H = Mod:avp_header(AvpName),
-    [diameter_codec:pack_data(H, Mod:avp(encode, V, AvpName, Opts))
-     || V <- Values].
+%% avp_header/2
+
+avp_header('AVP', _) ->
+    false;
+
+avp_header(AvpName, Mod) ->
+    {_,_,_} = Mod:avp_header(AvpName).
+
+%% enc1/6
+
+enc1(Name, 'AVP', false, Value, Opts, Mod) ->
+    enc_AVP(Name, Value, Opts, Mod);
+
+enc1(_, AvpName, Hdr, Value, Opts, Mod) ->
+    enc1(AvpName, Hdr, Value, Opts, Mod).
+
+%% enc1/5
+
+enc1(AvpName, {_,_,_} = Hdr, Value, Opts, Mod) ->
+    diameter_codec:pack_data(Hdr, Mod:avp(encode, Value, AvpName, Opts)).
 
 %% enc_AVP/4
 
@@ -153,48 +212,190 @@ enc_AVP(_, #diameter_avp{name = N, value = V}, _, _)
 enc_AVP(Name, #diameter_avp{name = AvpName, value = Data}, Opts, Mod) ->
     0 == Mod:avp_arity(Name, AvpName)
         orelse ?THROW([known_avp_as_AVP, Name, AvpName, Data]),
-    enc(AvpName, [Data], Opts, Mod);
+    enc(AvpName, Data, Opts, Mod);
 
 %% The backdoor ...
 enc_AVP(_, {AvpName, Value}, Opts, Mod) ->
-    enc(AvpName, [Value], Opts, Mod);
+    enc(AvpName, Value, Opts, Mod);
 
 %% ... and the side door.
 enc_AVP(_Name, {_Dict, _AvpName, _Data} = T, Opts, _) ->
     diameter_codec:pack_avp(#diameter_avp{data = T}, Opts).
 
+%% enc/4
+
+enc(AvpName, Value, Opts, Mod) ->
+    enc1(AvpName, Mod:avp_header(AvpName), Value, Opts, Mod).
+
 %% ---------------------------------------------------------------------------
 %% # decode_avps/3
 %% ---------------------------------------------------------------------------
 
--spec decode_avps(parent_name(), [#diameter_avp{}], map())
+-spec decode_avps(parent_name(), binary(), map())
    -> {parent_record(), [avp()], Failed}
  when Failed :: [{5000..5999, #diameter_avp{}}].
 
-decode_avps(Name, Recs, #{module := Mod} = Opts) ->
-    {Avps, {Rec, Failed}}
-        = mapfoldl(fun(T,A) -> decode(Name, Opts, Mod, T, A) end,
-                   {newrec(Mod, Name), []},
-                   Recs),
-    {Rec, Avps, Failed ++ missing(Rec, Name, Failed, Opts, Mod)}.
-%% Append 5005 errors so that errors are reported in the order
+decode_avps(Name, Bin, #{module := Mod, decode_format := Fmt} = Opts) ->
+    Strict = mget(strict_arities, Opts, decode),
+    [AM, Avps, Failed | Rec]
+        = decode(Bin, Name, Mod, Fmt, Strict, Opts, #{}),
+    %% AM counts the number of top-level AVPs, which missing/5 then
+    %% uses when appending 5005 errors.
+    {reformat(Name, Rec, Strict, Mod, Fmt),
+     Avps,
+     Failed ++ missing(Name, Strict, Mod, Opts, AM)}.
+
+%% Append arity errors so that errors are reported in the order
 %% encountered. Failed-AVP should typically contain the first
-%% encountered error accordg to the RFC.
+%% error encountered.
+
+%% decode/7
 
-%% mapfoldl/3
+decode(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>,
+       Name,
+       Mod,
+       Fmt,
+       Strict,
+       Opts,
+       AM) ->
+    decode(Rest,
+           Code,
+           if 1 == V -> I; true -> undefined end,
+           Len - 8 - 4*V, %% possibly negative, causing case match to fail
+           (4 - (Len rem 4)) rem 4,
+           1 == M,
+           1 == P,
+           Name,
+           Mod,
+           Fmt,
+           Strict,
+           Opts,
+           AM);
+
+decode(<<>>, Name, Mod, Fmt, Strict, _, AM) ->
+    [AM, [], [] | newrec(Fmt, Mod, Name, Strict)];
+
+decode(Bin, Name, Mod, Fmt, Strict, _, AM) ->
+    Avp = #diameter_avp{data = Bin},
+    [AM, [Avp], [{5014, Avp}] | newrec(Fmt, Mod, Name, Strict)].
+
+%% decode/13
+
+decode(Bin, Code, Vid, DataLen, Pad, M, P, Name, Mod, Fmt, Strict, Opts0, AM0) ->
+    case Bin of
+        <<Data:DataLen/binary, _:Pad/binary, T/binary>> ->
+            {NameT, AvpName, Arity, {Idx, AM}}
+                = incr(Name, Code, Vid, M, Mod, Strict, Opts0, AM0),
+
+            Opts = setopts(NameT, Name, M, Opts0),
+            %% Not AvpName or else a failed Failed-AVP
+            %% decode is packed into 'AVP'.
+
+            Avp = #diameter_avp{code = Code,
+                                vendor_id = Vid,
+                                is_mandatory = M,
+                                need_encryption = P,
+                                data = Data,
+                                name = name(NameT),
+                                type = type(NameT),
+                                index = Idx},
+
+            Dec = decode(Data, Name, NameT, Mod, Opts, Avp),    %% decode
+            Acc = decode(T, Name, Mod, Fmt, Strict, Opts, AM),  %% recurse
+            acc(Acc, Dec, Name, AvpName, Arity, Strict, Mod, Opts);
+        _ ->
+            {NameT, _AvpName, _Arity, {Idx, AM}}
+                = incr(Name, Code, Vid, M, Mod, Strict, Opts0, AM0),
+
+            Avp = #diameter_avp{code = Code,
+                                vendor_id = Vid,
+                                is_mandatory = M,
+                                need_encryption = P,
+                                data = Bin,
+                                name = name(NameT),
+                                type = type(NameT),
+                                index = Idx},
+
+            [AM, [Avp], [{5014, Avp}] | newrec(Fmt, Mod, Name, Strict)]
+    end.
+
+%% incr/8
+
+incr(Name, Code, Vid, M, Mod, Strict, Opts, AM0) ->
+    NameT = Mod:avp_name(Code, Vid), %% {AvpName, Type} | 'AVP'
+    AvpName = field(NameT),
+    Arity = avp_arity(Name, AvpName, Mod, Opts, M),
+    {NameT, AvpName, Arity, incr(AvpName, Arity, Strict, AM0)}.
+
+%% Data is a truncated header if command_code = undefined, otherwise
+%% payload bytes. The former is padded to the length of a header if
+%% the AVP reaches an outgoing encode.
 %%
-%% Like lists:mapfoldl/3, but don't reverse the list.
+%% RFC 6733 says that an AVP returned with 5014 can contain a minimal
+%% payload for the AVP's type, but don't always know the type.
 
-mapfoldl(F, Acc, List) ->
-    mapfoldl(F, Acc, List, []).
+setopts('AVP', _, _, Opts) ->
+    Opts;
 
-mapfoldl(F, Acc0, [T|Rest], List) ->
-    {B, Acc} = F(T, Acc0),
-    mapfoldl(F, Acc, Rest, [B|List]);
-mapfoldl(_, Acc, [], List) ->
-    {List, Acc}.
+setopts({_, Type}, Name, M, Opts) ->
+    set_failed(Name, set_strict(Type, M, Opts)).
 
-%% 3588:
+%% incr/4
+
+incr(F, A, SA, AM)
+  when F == 'AVP';
+       A == ?ANY;
+       A == 0;
+       SA /= decode ->
+    {undefined, AM};
+
+incr(AvpName, _, _, AM) ->
+    case AM of
+        #{AvpName := N} ->
+            {N, AM#{AvpName => N+1}};
+        _ ->
+            {0, AM#{AvpName => 1}}
+    end.
+
+%% mget/3
+%%
+%% Measurably faster than maps:get/3.
+
+mget(Key, Map, Def) ->
+    case Map of
+        #{Key := V} ->
+            V;
+        _ ->
+            Def
+    end.
+
+%% name/1
+
+name({Name, _}) ->
+    Name;
+name(_) ->
+    undefined.
+
+%% type/1
+
+type({_, Type}) ->
+    Type;
+type(_) ->
+    undefined.
+
+%% missing/5
+
+missing(Name, decode, Mod, Opts, AM) ->
+    [{5005, empty_avp(N, Opts, Mod)} || {N,A} <- Mod:avp_arity(Name),
+                                        N /= 'AVP',
+                                        Mn <- [min_arity(A)],
+                                        0 < Mn,
+                                        mget(N, AM, 0) < Mn];
+
+missing(_, _, _, _, _) ->
+    [].
+
+%% 3588/6733:
 %%
 %%   DIAMETER_MISSING_AVP               5005
 %%      The request did not contain an AVP that is required by the Command
@@ -204,57 +405,20 @@ mapfoldl(_, Acc, [], List) ->
 %%      Vendor-Id if applicable.  The value field of the missing AVP
 %%      should be of correct minimum length and contain zeros.
 
-missing(Rec, Name, Failed, Opts, Mod) ->
-    Avps = lists:foldl(fun({_, #diameter_avp{code = C, vendor_id = V}}, A) ->
-                               maps:put({C,V}, true, A)
-                       end,
-                       maps:new(),
-                       Failed),
-    missing(Mod:avp_arity(Name), tl(tuple_to_list(Rec)), Avps, Opts, Mod, []).
-
-missing([{Name, Arity} | As], [Value | Vs], Avps, Opts, Mod, Acc) ->
-    missing(As,
-            Vs,
-            Avps,
-            Opts,
-            Mod,
-            case
-                [H || missing_arity(Arity, Value),
-                      {C,_,V} = H <- [Mod:avp_header(Name)],
-                      not maps:is_key({C,V}, Avps)]
-            of
-                [H] ->
-                    [{5005, empty_avp(Name, H, Opts, Mod)} | Acc];
-                [] ->
-                    Acc
-            end);
-
-missing([], [], _, _, _, Acc) ->
-    Acc.
-
-%% Maximum arities have already been checked in building the record.
-
-missing_arity(1, V) ->
-    V == undefined;
-missing_arity({0, _}, _) ->
-    false;
-missing_arity({1, _}, L) ->
-    [] == L;
-missing_arity({Min, _}, L) ->
-    not has_prefix(Min, L).
-
-%% Compare a non-negative integer and the length of a list without
-%% computing the length.
-has_prefix(0, _) ->
-    true;
-has_prefix(_, []) ->
-    false;
-has_prefix(N, [_|L]) ->
-    has_prefix(N-1, L).
+%% min_arity/1
+
+min_arity(1) ->
+    1;
+min_arity({Mn,_}) ->
+    Mn.
 
-%% empty_avp/4
+%% empty_avp/3
 
-empty_avp(Name, {Code, Flags, VId}, Opts, Mod) ->
+empty_avp('AVP', _, _) ->
+    #diameter_avp{data = <<0:64>>};
+
+empty_avp(Name, Opts, Mod) ->
+    {Code, Flags, VId} = Mod:avp_header(Name),
     {Name, Type} = Mod:avp_name(Code, VId),
     #diameter_avp{name = Name,
                   code = Code,
@@ -273,21 +437,18 @@ empty_avp(Name, {Code, Flags, VId}, Opts, Mod) ->
 %%   specific errors that can be described by this AVP are described in
 %%   the following section.
 
-%% decode/5
+%% field/1
 
-decode(Name,
-       Opts,
-       Mod,
-       #diameter_avp{code = Code, vendor_id = Vid}
-       = Avp,
-       Acc) ->
-    decode(Name, Opts, Mod, Mod:avp_name(Code, Vid), Avp, Acc).
+field({AvpName, _}) ->
+    AvpName;
+field(_) ->
+    'AVP'.
 
 %% decode/6
 
 %% AVP not in dictionary.
-decode(Name, Opts, Mod, 'AVP', Avp, Acc) ->
-    decode_AVP(Name, Avp, Opts, Mod, Acc);
+decode(_Data, _Name, 'AVP', _Mod, _Opts, Avp) ->
+    Avp;
 
 %% 6733, 4.4:
 %%
@@ -336,130 +497,70 @@ decode(Name, Opts, Mod, 'AVP', Avp, Acc) ->
 %% defined the RFC's "unrecognized", which is slightly stronger than
 %% "not defined".)
 
-decode(Name, Opts0, Mod, {AvpName, Type}, Avp, Acc) ->
-    #diameter_avp{data = Data, is_mandatory = M}
-        = Avp,
-
-    %% Whether or not to ignore an M-bit on an encapsulated AVP, or on
-    %% all AVPs with the service_opt() strict_mbit.
-    Opts1 = set_strict(Type, M, Opts0),
-
-    %% Whether or not we're decoding within Failed-AVP and should
-    %% ignore decode errors.
+decode(Data, Name, {AvpName, Type}, Mod, Opts, Avp) ->
     #{dictionary := AppMod, failed_avp := Failed}
-        = Opts
-        = set_failed(Name, Opts1), %% Not AvpName or else a failed Failed-AVP
-                                   %% decode is packed into 'AVP'.
+        = Opts,
 
     %% Reset the dictionary for best-effort decode of Failed-AVP.
-    DecMod = if Failed ->
-                     AppMod;
-                true ->
-                     Mod
+    DecMod = if Failed -> AppMod;
+                true   -> Mod
              end,
 
-    %% On decode, a Grouped AVP is represented as a #diameter_avp{}
-    %% list with AVP as head and component AVPs as tail. On encode,
-    %% data can be a list of component AVPs.
+    %% A Grouped AVP is represented as a #diameter_avp{} list with AVP
+    %% as head and component AVPs as tail. On encode, data can be a
+    %% list of component AVPs.
 
     try avp_decode(Data, AvpName, Opts, DecMod, Mod) of
         {Rec, As} when Type == 'Grouped' ->
-            A = Avp#diameter_avp{name = AvpName,
-                                 value = Rec,
-                                 type = Type},
-            {[A|As], pack_avp(Name, A, Opts, Mod, Acc)};
-
+            A = Avp#diameter_avp{value = Rec},
+            [A | As];
         V when Type /= 'Grouped' ->
-            A = Avp#diameter_avp{name = AvpName,
-                                 value = V,
-                                 type = Type},
-            {A, pack_avp(Name, A, Opts, Mod, Acc)}
+            Avp#diameter_avp{value = V}
     catch
-        throw: {?MODULE, {grouped, Error, ComponentAvps}} ->
-            decode_error(Name,
-                         Error,
-                         ComponentAvps,
-                         Opts,
-                         Mod,
-                         Avp#diameter_avp{name = AvpName,
-                                          data = trim(Avp#diameter_avp.data),
-                                          type = Type},
-                         Acc);
-
+        throw: {?MODULE, T} ->
+            decode_error(Failed, T, Avp);
         error: Reason ->
-            decode_error(Name,
-                         Reason,
-                         Opts,
-                         Mod,
-                         Avp#diameter_avp{name = AvpName,
-                                          data = trim(Avp#diameter_avp.data),
-                                          type = Type},
-                         Acc)
+            decode_error(Failed, Reason, Name, Mod, Opts, Avp)
     end.
 
-%% avp_decode/5
-
-avp_decode(Data, AvpName, Opts, Mod, Mod) ->
-    Mod:avp(decode, Data, AvpName, Opts);
-
-avp_decode(Data, AvpName, Opts, Mod, _) ->
-    Mod:avp(decode, Data, AvpName, Opts, Mod).
-
-%% trim/1
+%% decode_error/3
 %%
-%% Remove any extra bit that was added in diameter_codec to induce a
-%% 5014 error.
-
-trim(#diameter_avp{data = Data} = Avp) ->
-    Avp#diameter_avp{data = trim(Data)};
+%% Error when decoding a grouped AVP.
 
-trim({5014, Bin}) ->
-    Bin;
+decode_error(true, {Rec, _, _}, Avp) ->
+    Avp#diameter_avp{value = Rec};
 
-trim(Avps)
-  when is_list(Avps) ->
-    lists:map(fun trim/1, Avps);
+decode_error(false, {_, ComponentAvps, [{RC,A} | _]}, Avp) ->
+    {RC, [Avp | ComponentAvps], Avp#diameter_avp{data = [A]}}.
 
-trim(Avp) ->
-    Avp.
-
-%% decode_error/7
-
-decode_error(Name, [_ | Rec], _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp#diameter_avp{value = Rec}, Opts, Mod, Acc);
-
-decode_error(Name, _, _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp, Opts, Mod, Acc);
-
-decode_error(_, [Error | _], ComponentAvps, _, _, Avp, Acc) ->
-    decode_error(Error, Avp, Acc, ComponentAvps);
-
-decode_error(_, Error, ComponentAvps, _, _, Avp, Acc) ->
-    decode_error(Error, Avp, Acc, ComponentAvps).
-
-%% decode_error/5
+%% decode_error/6
+%%
+%% Error when decoding a non-grouped AVP.
 
-decode_error(Name, _Reason, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp, Opts, Mod, Acc);
+decode_error(true, _, _, _, _, Avp) ->
+    Avp;
 
-decode_error(Name, Reason, Opts, Mod, Avp, {Rec, Failed}) ->
+decode_error(false, Reason, Name, Mod, Opts, Avp) ->
     Stack = diameter_lib:get_stacktrace(),
     diameter_lib:log(decode_error,
                      ?MODULE,
                      ?LINE,
                      {Reason, Name, Avp#diameter_avp.name, Mod, Stack}),
-    {Avp, {Rec, [rc(Reason, Avp, Opts, Mod) | Failed]}}.
+    rc(Reason, Avp, Opts, Mod).
 
-%% decode_error/4
+%% avp_decode/5
 
-decode_error({RC, ErrorData}, Avp, {Rec, Failed}, ComponentAvps) ->
-    E = Avp#diameter_avp{data = [ErrorData]},
-    {[Avp | trim(ComponentAvps)], {Rec, [{RC, E} | Failed]}}.
+avp_decode(Data, AvpName, Opts, Mod, Mod) ->
+    Mod:avp(decode, Data, AvpName, Opts);
 
-%% set_strict/3
+avp_decode(Data, AvpName, Opts, Mod, _) ->
+    Mod:avp(decode, Data, AvpName, Opts, Mod).
 
+%% set_strict/3
+%%
 %% Set false as soon as we see a Grouped AVP that doesn't set the
 %% M-bit, to ignore the M-bit on an encapsulated AVP.
+
 set_strict('Grouped', false = M, #{strict_mbit := true} = Opts) ->
     Opts#{strict_mbit := M};
 set_strict(_, _, Opts) ->
@@ -476,102 +577,82 @@ set_failed('Failed-AVP', #{failed_avp := false} = Opts) ->
 set_failed(_, Opts) ->
     Opts.
 
-%% decode_AVP/5
-%%
-%% Don't know this AVP: see if it can be packed in an 'AVP' field
-%% undecoded. Note that the type field is 'undefined' in this case.
+%% acc/8
 
-decode_AVP(Name, Avp, Opts, Mod, Acc) ->
-    {trim(Avp), pack_AVP(Name, Avp, Opts, Mod, Acc)}.
-
-%% rc/2
-
-%% diameter_types will raise an error of this form to communicate
-%% DIAMETER_INVALID_AVP_LENGTH (5014). A module specified to a
-%% @custom_types tag in a dictionary file can also raise an error of
-%% this form.
-rc({'DIAMETER', 5014 = RC, _}, #diameter_avp{name = AvpName} = Avp, Opts, Mod) ->
-    {RC, Avp#diameter_avp{data = Mod:empty_value(AvpName, Opts)}};
-
-%% 3588:
-%%
-%%   DIAMETER_INVALID_AVP_VALUE         5004
-%%      The request contained an AVP with an invalid value in its data
-%%      portion.  A Diameter message indicating this error MUST include
-%%      the offending AVPs within a Failed-AVP AVP.
-rc(_, Avp, _, _) ->
-    {5004, Avp}.
+acc([AM | Acc], As, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [AM | acc1(Acc, As, Name, AvpName, Arity, Strict, Mod, Opts)].
 
-%% pack_avp/5
+%% acc1/8
 
-pack_avp(Name, #diameter_avp{name = AvpName} = Avp, Opts, Mod, Acc) ->
-    pack_avp(Name, Mod:avp_arity(Name, AvpName), Avp, Opts, Mod, Acc).
+%% Faulty AVP, not grouped.
+acc1(Acc, {_RC, Avp} = E, _, _, _, _, _, _) ->
+    [Avps, Failed | Rec] = Acc,
+    [[Avp | Avps], [E | Failed] | Rec];
 
-%% pack_avp/6
+%% Faulty component in grouped AVP.
+acc1(Acc, {RC, As, Avp}, _, _, _, _, _, _) ->
+    [Avps, Failed | Rec] = Acc,
+    [[As | Avps], [{RC, Avp} | Failed] | Rec];
 
-pack_avp(Name, 0, Avp, Opts, Mod, Acc) ->
-    pack_AVP(Name, Avp, Opts, Mod, Acc);
+%% Grouped AVP ...
+acc1([Avps | Acc], [Avp|_] = As, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [[As|Avps] | acc2(Acc, Avp, Name, AvpName, Arity, Strict, Mod, Opts)];
 
-pack_avp(_, Arity, #diameter_avp{name = AvpName} = Avp, _Opts, Mod, Acc) ->
-    pack(Arity, AvpName, Avp, Mod, Acc).
+%% ... or not.
+acc1([Avps | Acc], Avp, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [[Avp|Avps] | acc2(Acc, Avp, Name, AvpName, Arity, Strict, Mod, Opts)].
 
-%% pack_AVP/5
+%% acc2/8
 
-%% Length failure was induced because of a header/payload length
-%% mismatch. The AVP Length is reset to match the received data if
-%% this AVP is encoded in an answer message, since the length is
-%% computed.
-%%
-%% Data is a truncated header if command_code = undefined, otherwise
-%% payload bytes. The former is padded to the length of a header if
-%% the AVP reaches an outgoing encode in diameter_codec.
-%%
-%% RFC 6733 says that an AVP returned with 5014 can contain a minimal
-%% payload for the AVP's type, but in this case we don't know the
-%% type.
+%% No errors, but nowhere to pack.
+acc2(Acc, Avp, _, 'AVP', 0, _, _, _) ->
+    [Failed | Rec] = Acc,
+    [[{rc(Avp), Avp} | Failed] | Rec];
 
-pack_AVP(_, #diameter_avp{data = {5014 = RC, Data}} = Avp, _, _, Acc) ->
-    {Rec, Failed} = Acc,
-    {Rec, [{RC, Avp#diameter_avp{data = Data}} | Failed]};
+%% No AVP of this name: try to pack as 'AVP'.
+acc2(Acc, Avp, Name, AvpName, 0, Strict, Mod, Opts) ->
+    M = Avp#diameter_avp.is_mandatory,
+    Arity = pack_arity(Name, AvpName, Opts, Mod, M),
+    acc2(Acc, Avp, Name, 'AVP', Arity, Strict, Mod, Opts);
 
-pack_AVP(Name, Avp, Opts, Mod, Acc) ->
-    pack_arity(Name, pack_arity(Name, Opts, Mod, Avp), Avp, Mod, Acc).
+%% Relaxed arities.
+acc2(Acc, Avp, _, AvpName, Arity, Strict, Mod, _)
+  when Strict /= decode ->
+    pack(Arity, AvpName, Avp, Mod, Acc);
 
-%% pack_arity/5
+%% No maximum arity.
+acc2(Acc, Avp, _, AvpName, {_,'*'} = Arity, _, Mod, _) ->
+    pack(Arity, AvpName, Avp, Mod, Acc);
 
-pack_arity(_, 0, #diameter_avp{is_mandatory = M} = Avp, _, Acc) ->
-    {Rec, Failed} = Acc,
-    {Rec, [{if M -> 5001; true -> 5008 end, Avp} | Failed]};
+%% Or check.
+acc2(Acc, Avp, _, AvpName, Arity, _, Mod, _) ->
+    Mx = max_arity(Arity),
+    if Mx =< Avp#diameter_avp.index ->
+            [Failed | Rec] = Acc,
+            [[{5009, Avp} | Failed] | Rec];
+       true ->
+            pack(Arity, AvpName, Avp, Mod, Acc)
+    end.
 
-pack_arity(_, Arity, Avp, Mod, Acc) ->
-    pack(Arity, 'AVP', Avp, Mod, Acc).
+%% 3588/6733:
+%%
+%%   DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
+%%      A message was received that included an AVP that appeared more
+%%      often than permitted in the message definition.  The Failed-AVP
+%%      AVP MUST be included and contain a copy of the first instance of
+%%      the offending AVP that exceeded the maximum number of occurrences
 
-%% Give Failed-AVP special treatment since (1) it'll contain any
-%% unrecognized mandatory AVP's and (2) the RFC 3588 grammar failed to
-%% allow for Failed-AVP in an answer-message.
+%% max_arity/1
 
-pack_arity(Name,
-           #{strict_mbit := Strict,
-             failed_avp := Failed},
-           Mod,
-           #diameter_avp{is_mandatory = M,
-                         name = AvpName}) ->
+max_arity(1) ->
+    1;
+max_arity({_,Mx}) ->
+    Mx.
 
-    %% Not testing just Name /= 'Failed-AVP' means we're changing the
-    %% packing of AVPs nested within Failed-AVP, but the point of
-    %% ignoring errors within Failed-AVP is to decode as much as
-    %% possible, and failing because a mandatory AVP couldn't be
-    %% packed into a dedicated field defeats that point.
+%% rc/1
 
-    if Failed == true;
-       Name == 'Failed-AVP';
-       Name == 'answer-message', AvpName == 'Failed-AVP';
-       not M;
-       not Strict ->
-            Mod:avp_arity(Name, 'AVP');
-       true ->
-            0
-    end.
+rc(#diameter_avp{is_mandatory = M}) ->
+    if M -> 5001; true -> 5008 end.
 
 %% 3588:
 %%
@@ -586,75 +667,114 @@ pack_arity(Name,
 %%      Failed-AVP AVP MUST be included and contain a copy of the
 %%      offending AVP.
 
-%% pack/5
+%% pack_arity/5
+
+%% Give Failed-AVP special treatment since (1) it'll contain any
+%% unrecognized mandatory AVP's and (2) the RFC 3588 grammar failed to
+%% allow for Failed-AVP in an answer-message.
+
+pack_arity(Name, AvpName, _, Mod, M)
+  when Name == 'Failed-AVP';
+       Name == 'answer-message', AvpName == 'Failed-AVP';
+       not M ->
+    Mod:avp_arity(Name, 'AVP');
+%% Not testing just Name /= 'Failed-AVP' means we're changing the
+%% packing of AVPs nested within Failed-AVP, but the point of
+%% ignoring errors within Failed-AVP is to decode as much as
+%% possible, and failing because a mandatory AVP couldn't be
+%% packed into a dedicated field defeats that point.
+
+pack_arity(Name, _, #{strict_mbit := Strict, failed_avp := Failed}, Mod, _)
+  when not Strict;
+       Failed ->
+    Mod:avp_arity(Name, 'AVP');
+
+pack_arity(_, _, _, _, _) ->
+    0.
 
-pack(Arity, FieldName, Avp, Mod, {Rec, _} = Acc) ->
-    pack(Mod:'#get-'(FieldName, Rec), Arity, FieldName, Avp, Mod, Acc).
+%% avp_arity/5
 
-%% pack/6
+avp_arity(Name, 'AVP' = AvpName, Mod, Opts, M) ->
+    pack_arity(Name, AvpName, Opts, Mod, M);
 
-pack(undefined, 1, 'AVP' = F, Avp, Mod, {Rec, Failed}) ->  %% unlikely
-    {Mod:'#set-'({F, Avp}, Rec), Failed};
+avp_arity(Name, AvpName, Mod, _, _) ->
+    Mod:avp_arity(Name, AvpName).
 
-pack(undefined, 1, F, #diameter_avp{value = V}, Mod, {Rec, Failed}) ->
-    {Mod:'#set-'({F, V}, Rec), Failed};
+%% rc/4
+
+%% Length error communicated from diameter_types or a
+%% @custom_types/@codecs module.
+rc({'DIAMETER', 5014 = RC, _}, #diameter_avp{name = AvpName} = A, Opts, Mod) ->
+    {RC, A#diameter_avp{data = Mod:empty_value(AvpName, Opts)}};
 
 %% 3588:
 %%
-%%   DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
-%%      A message was received that included an AVP that appeared more
-%%      often than permitted in the message definition.  The Failed-AVP
-%%      AVP MUST be included and contain a copy of the first instance of
-%%      the offending AVP that exceeded the maximum number of occurrences
-%%
+%%   DIAMETER_INVALID_AVP_VALUE         5004
+%%      The request contained an AVP with an invalid value in its data
+%%      portion.  A Diameter message indicating this error MUST include
+%%      the offending AVPs within a Failed-AVP AVP.
+rc(_, Avp, _, _) ->
+    {5004, Avp}.
 
-pack(_, 1, _, Avp, _, {Rec, Failed}) ->
-    {Rec, [{5009, Avp} | Failed]};
-
-pack(L, {_, Max}, F, Avp, Mod, {Rec, Failed}) ->
-    case '*' /= Max andalso has_prefix(Max+1, L) of
-        true ->
-            {Rec, [{5009, Avp} | Failed]};
-        false when F == 'AVP' ->
-            {Mod:'#set-'({F, [Avp | L]}, Rec), Failed};
-        false ->
-            {Mod:'#set-'({F, [Avp#diameter_avp.value | L]}, Rec), Failed}
-    end.
+%% pack/5
+
+pack(Arity, F, Avp, Mod, [Failed | Rec]) ->
+    [Failed | set(Arity, F, value(F, Avp), Mod, Rec)].
+
+%% set/5
+
+set(_, _, _, _, false = No) ->
+    No;
+
+set(1, F, Value, _, Map)
+  when is_map(Map) ->
+    Map#{F => Value};
+
+set(_, F, V, _, Map)
+  when is_map(Map) ->
+    maps:update_with(F, fun(Vs) -> [V|Vs] end, [V], Map);
+
+set(1, F, Value, Mod, Rec) ->
+    Mod:'#set-'({F, Value}, Rec);
+
+set(_, F, V, Mod, Rec) ->
+    Vs = Mod:'#get-'(F, Rec),
+    Mod:'#set-'({F, [V|Vs]}, Rec).
+
+%% value/2
+
+value('AVP', Avp) ->
+    Avp;
+
+value(_, #diameter_avp{value = V}) ->
+    V.
 
 %% ---------------------------------------------------------------------------
 %% # grouped_avp/3
 %% ---------------------------------------------------------------------------
 
--spec grouped_avp(decode, avp_name(), binary() | {5014, binary()}, term())
+%% Note that Grouped is the only AVP type that doesn't just return a
+%% decoded value, also returning the list of component diameter_avp
+%% records.
+
+-spec grouped_avp(decode, avp_name(), binary(), term())
    -> {avp_record(), [avp()]};
                  (encode, avp_name(), avp_record() | avp_values(), term())
    -> iolist()
     | no_return().
 
-%% Length error induced by diameter_codec:collect_avps/1: the AVP
-%% length in the header was too short (insufficient for the extracted
-%% header) or too long (past the end of the message). An empty payload
-%% is sufficient according to the RFC text for 5014.
-grouped_avp(decode, _Name, {5014 = RC, _Bin}, _) ->
-    ?THROW({grouped, {RC, []}, []});
-
-grouped_avp(decode, Name, Data, Opts) ->
-    grouped_decode(Name, diameter_codec:collect_avps(Data), Opts);
+%% An error in decoding a component AVP throws the first faulty
+%% component, which a catch wraps in the Grouped AVP in question. A
+%% partially decoded record is only used when ignoring errors in
+%% Failed-AVP.
+grouped_avp(decode, Name, Bin, Opts) ->
+    {Rec, Avps, Es} = T = decode_avps(Name, Bin, Opts),
+    [] == Es orelse ?THROW(T),
+    {Rec, Avps};
 
 grouped_avp(encode, Name, Data, Opts) ->
     encode_avps(Name, Data, Opts).
 
-%% grouped_decode/2
-%%
-%% Note that Grouped is the only AVP type that doesn't just return a
-%% decoded value, also returning the list of component diameter_avp
-%% records.
-
-%% Length error in trailing component AVP.
-grouped_decode(_Name, {Error, Acc}, _) ->
-    {5014, Avp} = Error,
-    ?THROW({grouped, Error, [Avp | Acc]});
-
 %% 7.5.  Failed-AVP AVP
 
 %%    In the case where the offending AVP is embedded within a Grouped AVP,
@@ -665,15 +785,6 @@ grouped_decode(_Name, {Error, Acc}, _) ->
 %%    to the single offending AVP.  This enables the recipient to detect
 %%    the location of the offending AVP when embedded in a group.
 
-%% An error in decoding a component AVP throws the first faulty
-%% component, which the catch in d/3 wraps in the Grouped AVP in
-%% question. A partially decoded record is only used when ignoring
-%% errors in Failed-AVP.
-grouped_decode(Name, ComponentAvps, Opts) ->
-    {Rec, Avps, Es} = decode_avps(Name, ComponentAvps, Opts),
-    [] == Es orelse ?THROW({grouped, [{_,_} = hd(Es) | Rec], Avps}),
-    {Rec, Avps}.
-
 %% ---------------------------------------------------------------------------
 %% # empty_group/2
 %% ---------------------------------------------------------------------------
@@ -705,5 +816,45 @@ empty(Name, #{module := Mod} = Opts) ->
 
 %% ------------------------------------------------------------------------------
 
+%% newrec/4
+
+newrec(false = No, _, _, _) ->
+    No;
+
+newrec(record, Mod, Name, T)
+  when T /= decode ->
+    RecName = Mod:name2rec(Name),
+    Sz = Mod:'#info-'(RecName, size),
+    erlang:make_tuple(Sz, [], [{1, RecName}]);
+
+newrec(record, Mod, Name, _) ->
+    newrec(Mod, Name);
+
+newrec(_, _, _, _) ->
+    #{}.
+
+%% newrec/2
+
 newrec(Mod, Name) ->
     Mod:'#new-'(Mod:name2rec(Name)).
+
+%% reformat/5
+
+reformat(Name, Map, _Strict, Mod, list) ->
+    [{F,V} || {F,_} <- Mod:avp_arity(Name), #{F := V} <- [Map]];
+
+reformat(Name, Map, Strict, Mod, record_from_map) ->
+    RecName = Mod:name2rec(Name),
+    list_to_tuple([RecName | [mget(F, Map, def(A, Strict))
+                              || {F,A} <- Mod:avp_arity(Name)]]);
+
+reformat(_, Rec, _, _, _) ->
+    Rec.
+
+%% def/2
+
+def(1, decode) ->
+    undefined;
+
+def(_, _) ->
+    [].
diff --git a/lib/diameter/src/base/diameter_peer_fsm.erl b/lib/diameter/src/base/diameter_peer_fsm.erl
index e43b3f54cf..9115630eb5 100644
--- a/lib/diameter/src/base/diameter_peer_fsm.erl
+++ b/lib/diameter/src/base/diameter_peer_fsm.erl
@@ -128,7 +128,9 @@
                        %% outgoing DPR; boolean says whether or not
                        %% the request was sent explicitly with
                        %% diameter:call/4.
-         codec :: #{string_decode := boolean(),
+         codec :: #{decode_format := record,
+                    string_decode := boolean(),
+                    strict_arities => diameter:strict_arities(),
                     strict_mbit := boolean(),
                     rfc := 3588 | 6733,
                     ordered_encode := false},
@@ -253,11 +255,13 @@ i({Ack, WPid, {M, Ref} = T, Opts, {SvcOpts, Nodes, Dict0, Svc}}) ->
            length_errors = LengthErr,
            strict = Strictness,
            incoming_maxlen = Maxlen,
-           codec = maps:with([string_decode,
+           codec = maps:with([decode_format,
+                              string_decode,
                               strict_mbit,
                               rfc,
                               ordered_encode],
-                             SvcOpts#{ordered_encode => false})}.
+                             SvcOpts#{ordered_encode => false,
+                                      decode_format => record})}.
 %% The transport returns its local ip addresses so that different
 %% transports on the same service can use different local addresses.
 %% The local addresses are put into Host-IP-Address avps here when
@@ -655,10 +659,6 @@ encode(Rec, Opts, Dict) ->
 
 %% incoming/2
 
-incoming({recv = T, Name, Pkt}, #state{parent = Pid, ack = Ack} = S) ->
-    Pid ! {T, self(), get_route(Ack, Name, Pkt), Name, Pkt},
-    rcv(Name, Pkt, S);
-
 incoming(#diameter_header{is_request = R}, #state{transport = TPid,
                                                   ack = Ack}) ->
     R andalso Ack andalso send(TPid, false),
@@ -676,98 +676,97 @@ incoming(T, _) ->
 
 %% recv/2
 
-recv(#diameter_packet{header = #diameter_header{} = Hdr}
-     = Pkt,
-     #state{dictionary = Dict0}
-     = S) ->
-    recv1(diameter_codec:msg_name(Dict0, Hdr), Pkt, S);
-
-recv(#diameter_packet{header = undefined,
-                      bin = Bin}
-     = Pkt,
-     S) ->
-    recv(diameter_codec:decode_header(Bin), Pkt, S);
+recv(#diameter_packet{bin = Bin} = Pkt, S) ->
+    recv(Bin, Pkt, S);
 
 recv(Bin, S) ->
-    recv(#diameter_packet{bin = Bin}, S).
+    recv(Bin, Bin, S).
+
+%% recv/3
+
+recv(Bin, Msg, S) ->
+    recv(diameter_codec:decode_header(Bin), Bin, Msg, S).
+
+%% recv/4
 
-%% recv1/3
+recv(false, Bin, _, #state{length_errors = E}) ->
+    invalid(E, truncated_header, Bin),
+    Bin;
+
+recv(#diameter_header{length = Len} = H, Bin, Msg, #state{length_errors = E,
+                                                          incoming_maxlen = M,
+                                                          dictionary = Dict0}
+                                                   = S)
+  when E == handle;
+       0 == Len rem 4, bit_size(Bin) == 8*Len, size(Bin) =< M ->
+    recv1(diameter_codec:msg_name(Dict0, H), H, Msg, S);
 
-recv1(_,
-      #diameter_packet{header = H, bin = Bin},
-      #state{incoming_maxlen = M})
+recv(H, Bin, _, #state{incoming_maxlen = M})
   when M < size(Bin) ->
     invalid(false, incoming_maxlen_exceeded, {size(Bin), H}),
     H;
 
+recv(H, Bin, _, #state{length_errors = E}) ->
+    T = {size(Bin), bit_size(Bin) rem 8, H},
+    invalid(E, message_length_mismatch, T),
+    H.
+
+%% recv1/4
+
 %% Ignore anything but an expected CER/CEA if so configured. This is
 %% non-standard behaviour.
-recv1(Name, #diameter_packet{header = H}, #state{state = {'Wait-CEA', _, _},
-                                                 strict = false})
+recv1(Name, H, _, #state{state = {'Wait-CEA', _, _},
+                         strict = false})
   when Name /= 'CEA' ->
     H;
-recv1(Name, #diameter_packet{header = H}, #state{state = recv_CER,
-                                                 strict = false})
+recv1(Name, H, _, #state{state = recv_CER,
+                         strict = false})
   when Name /= 'CER' ->
     H;
 
 %% Incoming request after outgoing DPR: discard. Don't discard DPR, so
 %% both ends don't do so when sending simultaneously.
-recv1(Name,
-      #diameter_packet{header = #diameter_header{is_request = true} = H},
-      #state{dpr = {_,_,_}})
+recv1(Name, #diameter_header{is_request = true} = H, _, #state{dpr = {_,_,_}})
   when Name /= 'DPR' ->
     invalid(false, recv_after_outgoing_dpr, H),
     H;
 
 %% Incoming request after incoming DPR: discard.
-recv1(_,
-      #diameter_packet{header = #diameter_header{is_request = true} = H},
-      #state{dpr = true}) ->
+recv1(_, #diameter_header{is_request = true} = H, _, #state{dpr = true}) ->
     invalid(false, recv_after_incoming_dpr, H),
     H;
 
 %% DPA with identifier mismatch, or in response to a DPR initiated by
 %% the service.
-recv1('DPA' = N,
-      #diameter_packet{header = #diameter_header{hop_by_hop_id = Hid,
-                                                 end_to_end_id = Eid}}
-      = Pkt,
-      #state{dpr = {X,H,E}}
+recv1('DPA' = Name,
+      #diameter_header{hop_by_hop_id = Hid, end_to_end_id = Eid}
+      = H,
+      Msg,
+      #state{dpr = {X,HI,EI}}
       = S)
-  when H /= Hid;
-       E /= Eid;
+  when HI /= Hid;
+       EI /= Eid;
        not X ->
-    rcv(N, Pkt, S);
+    Pkt = pkt(H, Msg),
+    handle(Name, Pkt, S);
 
-%% Any other message with a header and no length errors: send to the
-%% parent.
-recv1(Name, Pkt, #state{}) ->
-    {recv, Name, Pkt}.
+%% Any other message with a header and no length errors.
+recv1(Name, H, Msg, #state{parent = Pid, ack = Ack} = S) ->
+    Pkt = pkt(H, Msg),
+    Pid ! {recv, self(), get_route(Ack, Name, Pkt), Name, Pkt},
+    handle(Name, Pkt, S).
 
-%% recv/3
+%% pkt/2
 
-recv(#diameter_header{length = Len}
-     = H,
-     #diameter_packet{bin = Bin}
-     = Pkt,
-     #state{length_errors = E}
-     = S)
-  when E == handle;
-       0 == Len rem 4, bit_size(Bin) == 8*Len ->
-    recv(Pkt#diameter_packet{header = H}, S);
+pkt(H, Bin)
+  when is_binary(Bin) ->
+    #diameter_packet{header = H,
+                     bin = Bin};
 
-recv(#diameter_header{}
-     = H,
-     #diameter_packet{bin = Bin},
-     #state{length_errors = E}) ->
-    T = {size(Bin), bit_size(Bin) rem 8, H},
-    invalid(E, message_length_mismatch, T),
-    Bin;
+pkt(H, Pkt) ->
+    Pkt#diameter_packet{header = H}.
 
-recv(false, #diameter_packet{bin = Bin}, #state{length_errors = E}) ->
-    invalid(E, truncated_header, Bin),
-    Bin.
+%% invalid/3
 
 %% Note that counters here only count discarded messages.
 invalid(E, Reason, T) ->
@@ -776,39 +775,39 @@ invalid(E, Reason, T) ->
     ?LOG(Reason, T),
     ok.
 
-%% rcv/3
+%% handle/3
 
 %% Incoming CEA.
-rcv('CEA' = N,
-    #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
-                                               hop_by_hop_id = Hid}}
-    = Pkt,
-    #state{state = {'Wait-CEA', Hid, Eid}}
-    = S) ->
+handle('CEA' = N,
+       #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
+                                                  hop_by_hop_id = Hid}}
+       = Pkt,
+       #state{state = {'Wait-CEA', Hid, Eid}}
+       = S) ->
     ?LOG(recv, N),
     handle_CEA(Pkt, S);
 
 %% Incoming CER
-rcv('CER' = N, Pkt, #state{state = recv_CER} = S) ->
+handle('CER' = N, Pkt, #state{state = recv_CER} = S) ->
     handle_request(N, Pkt, S);
 
 %% Anything but CER/CEA in a non-Open state is an error, as is
 %% CER/CEA in anything but recv_CER/Wait-CEA.
-rcv(Name, _, #state{state = PS})
+handle(Name, _, #state{state = PS})
   when PS /= 'Open';
        Name == 'CER';
        Name == 'CEA' ->
     {stop, {Name, PS}};
 
-rcv('DPR' = N, Pkt, S) ->
+handle('DPR' = N, Pkt, S) ->
     handle_request(N, Pkt, S);
 
 %% DPA in response to DPR, with the expected identifiers.
-rcv('DPA' = N,
-    #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
-                                               hop_by_hop_id = Hid}
-                            = H}
-    = Pkt,
+handle('DPA' = N,
+       #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
+                                                  hop_by_hop_id = Hid}
+                               = H}
+       = Pkt,
     #state{dictionary = Dict0,
            transport = TPid,
            dpr = {X, Hid, Eid},
@@ -827,13 +826,13 @@ rcv('DPA' = N,
 %% Ignore an unsolicited DPA in particular. Note that dpa_timeout
 %% deals with the case in which the peer sends the wrong identifiers
 %% in DPA.
-rcv('DPA' = N, #diameter_packet{header = H}, _) ->
+handle('DPA' = N, #diameter_packet{header = H}, _) ->
     ?LOG(ignored, N),
     %% Note that these aren't counted in the normal recv counter.
     diameter_stats:incr({diameter_codec:msg_id(H), recv, ignored}),
     ok;
 
-rcv(_, _, _) ->
+handle(_, _, _) ->
     ok.
 
 %% incr/3
diff --git a/lib/diameter/src/base/diameter_service.erl b/lib/diameter/src/base/diameter_service.erl
index 788f697627..208e2e8cb8 100644
--- a/lib/diameter/src/base/diameter_service.erl
+++ b/lib/diameter/src/base/diameter_service.erl
@@ -112,7 +112,10 @@
                       use_shared_peers := diameter:remotes(),%% use from
                       restrict_connections := diameter:restriction(),
                       incoming_maxlen := diameter:message_length(),
+                      strict_arities => diameter:strict_arities(),
                       strict_mbit := boolean(),
+                      decode_format := diameter:decode_format(),
+                      traffic_counters := boolean(),
                       string_decode := boolean(),
                       spawn_opt := list() | {module(), atom(), list()}}}).
 
@@ -707,7 +710,7 @@ init_peers() ->
                                %%  TPid}
 
 service_options(Opts) ->
-    maps:from_list(Opts).
+    maps:from_list(lists:delete({strict_arities, true}, Opts)).
 
 mref(false = No) ->
     No;
diff --git a/lib/diameter/src/base/diameter_traffic.erl b/lib/diameter/src/base/diameter_traffic.erl
index 85378babea..27a41d6eb0 100644
--- a/lib/diameter/src/base/diameter_traffic.erl
+++ b/lib/diameter/src/base/diameter_traffic.erl
@@ -70,13 +70,16 @@
          timeout = 5000 :: 0..16#FFFFFFFF,  %% for outgoing requests
          detach = false :: boolean()}).
 
-%% Term passed back to receive_message/6 with every incoming message.
+%% Term passed back to receive_message/5 with every incoming message.
 -record(recvdata,
         {peerT        :: ets:tid(),
          service_name :: diameter:service_name(),
          apps         :: [#diameter_app{}],
          sequence     :: diameter:sequence(),
-         codec        :: #{string_decode := boolean(),
+         counters     :: boolean(),
+         codec        :: #{decode_format := diameter:decode_format(),
+                           string_decode := boolean(),
+                           strict_arities => diameter:strict_arities(),
                            strict_mbit := boolean(),
                            incoming_maxlen := diameter:message_length()}}).
 %% Note that incoming_maxlen is currently handled in diameter_peer_fsm,
@@ -96,13 +99,16 @@
 %% ---------------------------------------------------------------------------
 
 make_recvdata([SvcName, PeerT, Apps, SvcOpts | _]) ->
-    #{sequence := {_,_} = Mask, spawn_opt := Opts}
+    #{sequence := {_,_} = Mask, spawn_opt := Opts, traffic_counters := B}
         = SvcOpts,
     {Opts, #recvdata{service_name = SvcName,
                      peerT = PeerT,
                      apps = Apps,
                      sequence = Mask,
-                     codec = maps:with([string_decode,
+                     counters = B,
+                     codec = maps:with([decode_format,
+                                        string_decode,
+                                        strict_arities,
                                         strict_mbit,
                                         ordered_encode,
                                         incoming_maxlen],
@@ -182,7 +188,7 @@ incr_error(Dir, Id, TPid) ->
 %% ---------------------------------------------------------------------------
 
 -spec incr_rc(send|recv, Pkt, TPid, DictT)
-   -> {Counter, non_neg_integer()}
+   -> Counter
     | Reason
  when Pkt :: #diameter_packet{},
       TPid :: pid(),
@@ -193,18 +199,26 @@ incr_error(Dir, Id, TPid) ->
                | {'Experimental-Result', integer(), integer()},
       Reason :: atom().
 
-incr_rc(Dir, Pkt, TPid, {_, AppDict, _} = DictT) ->
-    try
-        incr_result(Dir, Pkt, TPid, DictT)
+incr_rc(Dir, Pkt, TPid, {MsgDict, AppDict, Dict0}) ->
+    incr_rc(Dir, Pkt, TPid, MsgDict, AppDict, Dict0);
+
+incr_rc(Dir, Pkt, TPid, Dict0) ->
+    incr_rc(Dir, Pkt, TPid, Dict0, Dict0, Dict0).
+
+%% incr_rc/6
+
+incr_rc(Dir, Pkt, TPid, MsgDict, AppDict, Dict0) ->
+    try get_result(Dir, MsgDict, Dict0, Pkt) of
+        false ->
+            unknown;
+        Avp ->
+            incr_result(Dir, Avp, Pkt, TPid, AppDict)
     catch
         exit: {E,_} when E == no_result_code;
                          E == invalid_error_bit ->
             incr(TPid, {msg_id(Pkt#diameter_packet.header, AppDict), Dir, E}),
             E
-    end;
-
-incr_rc(Dir, Pkt, TPid, Dict0) ->
-    incr_rc(Dir, Pkt, TPid, {Dict0, Dict0, Dict0}).
+    end.
 
 %% ---------------------------------------------------------------------------
 %% receive_message/5
@@ -216,13 +230,13 @@ incr_rc(Dir, Pkt, TPid, Dict0) ->
    -> pid()     %% request handler
     | boolean() %% answer, known request or not
     | discard   %% request discarded by MFA
- when Route :: {Handler, RequestRef, Seqs}
+ when Route :: {Handler, RequestRef, TPid}
              | Ack,
       RecvData :: {[SpawnOpt], #recvdata{}},
       SpawnOpt :: term(),
       Handler :: pid(),
       RequestRef :: reference(),
-      Seqs :: {0..16#FFFFFFFF, 0..16#FFFFFFFF},
+      TPid :: pid(),
       Ack :: boolean().
 
 receive_message(TPid, Route, Pkt, Dict0, RecvData) ->
@@ -303,14 +317,15 @@ recv_request(Ack,
              = Pkt,
              Dict0,
              #recvdata{peerT = PeerT,
-                       apps = Apps}
+                       apps = Apps,
+                       counters = Count}
              = RecvData) ->
     Ack andalso (TPid ! {handler, self()}),
     case diameter_service:find_incoming_app(PeerT, TPid, Id, Apps) of
         {#diameter_app{id = Aid, dictionary = AppDict} = App, Caps} ->
-            incr(recv, Pkt, TPid, AppDict),
+            Count andalso incr(recv, Pkt, TPid, AppDict),
             DecPkt = decode(Aid, AppDict, RecvData, Pkt),
-            incr_error(recv, DecPkt, TPid, AppDict),
+            Count andalso incr_error(recv, DecPkt, TPid, AppDict),
             send_A(recv_R(App, TPid, Dict0, Caps, RecvData, DecPkt),
                    TPid,
                    App,
@@ -323,9 +338,7 @@ recv_request(Ack,
             %%      A request was sent for an application that is not
             %%      supported.
             RC = 3007,
-            Es = Pkt#diameter_packet.errors,
-            DecPkt = Pkt#diameter_packet{avps = collect_avps(Pkt),
-                                         errors = [RC | Es]},
+            DecPkt = diameter_codec:collect_avps(Pkt),
             send_answer(answer_message(RC, Dict0, Caps, DecPkt),
                         TPid,
                         Dict0,
@@ -341,14 +354,6 @@ recv_request(Ack,
 decode(Id, Dict, #recvdata{codec = Opts}, Pkt) ->
     errors(Id, diameter_codec:decode(Id, Dict, Opts, Pkt)).
 
-collect_avps(Pkt) ->
-    case diameter_codec:collect_avps(Pkt) of
-        {_Error, Avps} ->
-            Avps;
-        Avps ->
-            Avps
-    end.
-
 %% send_A/7
 
 send_A([T | Fs], TPid, App, Dict0, RecvData, DecPkt, Caps) ->
@@ -541,6 +546,7 @@ send_A({call, Opts}, TPid, App, Dict0, RecvData, Pkt, Caps, Fs) ->
                         MsgDict,
                         AppDict,
                         Dict0,
+                        RecvData#recvdata.counters,
                         Fs);
         RC ->
             send_answer(answer_message(RC, Dict0, Caps, Pkt),
@@ -584,14 +590,22 @@ send_answer(Ans, TPid, MsgDict, AppDict, Dict0, RecvData, DecPkt, Fs) ->
                  TPid,
                  RecvData#recvdata.codec,
                  make_answer_packet(Ans, DecPkt, MsgDict, Dict0)),
-    send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, Fs).
+    send_answer(Pkt,
+                TPid,
+                MsgDict,
+                AppDict,
+                Dict0,
+                RecvData#recvdata.counters,
+                Fs).
 
-%% send_answer/6
+%% send_answer/7
 
-send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, [EvalPktFs | EvalFs]) ->
+send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, Count, [EvalPktFs | EvalFs]) ->
     eval_packet(Pkt, EvalPktFs),
-    incr(send, Pkt, TPid, AppDict),
-    incr_rc(send, Pkt, TPid, {MsgDict, AppDict, Dict0}),  %% count outgoing
+    Count andalso begin
+                      incr(send, Pkt, TPid, AppDict),
+                      incr_rc(send, Pkt, TPid, MsgDict, AppDict, Dict0)
+                  end,
     send(TPid, z(Pkt), _Route = self()),
     lists:foreach(fun diameter_lib:eval/1, EvalFs).
 
@@ -619,7 +633,7 @@ is_answer_message(#diameter_packet{msg = Msg}, Dict0) ->
 is_answer_message([#diameter_header{is_request = R, is_error = E} | _], _) ->
     E andalso not R;
 
-%% Message sent as a tagged avp/value list.
+%% Message sent as a map or tagged avp/value list.
 is_answer_message([Name | _], _) ->
     Name == 'answer-message';
 
@@ -867,7 +881,10 @@ reset(Msg, [RC | Avps], Dict) ->
 
 %% set/3
 
-%% Reply as name and tuple list ...
+%% Reply as name/values list ...
+set([Name|As], Avps, _)
+  when is_map(As) ->
+    [Name | maps:merge(As, maps:from_list(Avps))];
 set([_|_] = Ans, Avps, _) ->
     Ans ++ Avps;  %% Values nearer tail take precedence.
 
@@ -900,33 +917,44 @@ failed_avp(_, [] = No, _) ->
 failed_avp(Msg, [_|_] = Avps, Dict) ->
     [failed(Msg, [{'AVP', Avps}], Dict)].
 
-%% Reply as name and tuple list ...
-failed([MsgName | Values], FailedAvp, Dict) ->
-    RecName = Dict:msg2rec(MsgName),
+%% failed/3
+
+failed(Msg, FailedAvp, Dict) ->
+    RecName = msg2rec(Msg, Dict),
     try
-        Dict:'#info-'(RecName, {index, 'Failed-AVP'}),
+        Dict:'#info-'(RecName, {index, 'Failed-AVP'}), %% assert existence
         {'Failed-AVP', [FailedAvp]}
     catch
         error: _ ->
-            Avps = proplists:get_value('AVP', Values, []),
+            Avps = values(Msg, 'AVP', Dict),
             A = #diameter_avp{name = 'Failed-AVP',
                               value = FailedAvp},
             {'AVP', [A|Avps]}
+    end.
+
+%% msg2rec/2
+
+%% Message as name/values list ...
+msg2rec([MsgName | _], Dict) ->
+    Dict:msg2rec(MsgName);
+
+%% ... or record.
+msg2rec(Rec, _) ->
+    element(1, Rec).
+
+%% values/2
+
+%% Message as name/values list ...
+values([_ | Avps], F, _) ->
+    if is_map(Avps) ->
+            maps:get(F, Avps, []);
+       is_list(Avps) ->
+            proplists:get_value(F, Avps, [])
     end;
 
 %% ... or record.
-failed(Rec, FailedAvp, Dict) ->
-    try
-        RecName = element(1, Rec),
-        Dict:'#info-'(RecName, {index, 'Failed-AVP'}),
-        {'Failed-AVP', [FailedAvp]}
-    catch
-        error: _ ->
-            Avps = Dict:'#get-'('AVP', Rec),
-            A = #diameter_avp{name = 'Failed-AVP',
-                              value = FailedAvp},
-            {'AVP', [A|Avps]}
-    end.
+values(Rec, F, Dict) ->
+    Dict:'#get-'(F, Rec).
 
 %% 3.  Diameter Header
 %%
@@ -1102,48 +1130,31 @@ find_avp(Code, VId, [_ | Avps]) ->
 
 %% Message sent as a header/avps list.
 incr_result(send = Dir,
-            #diameter_packet{msg = [#diameter_header{} = H | _]}
-            = Pkt,
+            Avp,
+            #diameter_packet{msg = [#diameter_header{} = H | _]},
             TPid,
-            DictT) ->
-    incr_res(Dir, Pkt#diameter_packet{header = H}, TPid, DictT);
-
-%% Outgoing message as binary: don't count. (Sending binaries is only
-%% partially supported.)
-incr_result(send, #diameter_packet{header = undefined = No}, _, _) ->
-    No;
+            AppDict) ->
+    incr_result(Dir, Avp, H, [], TPid, AppDict);
 
 %% Incoming or outgoing. Outgoing with encode errors never gets here
 %% since encode fails.
-incr_result(Dir, Pkt, TPid, DictT) ->
-    incr_res(Dir, Pkt, TPid, DictT).
-
-incr_res(Dir,
-         #diameter_packet{header = #diameter_header{is_error = E}
-                          = Hdr,
-                          errors = Es}
-         = Pkt,
-         TPid,
-         DictT) ->
-    {MsgDict, AppDict, Dict0} = DictT,
+incr_result(Dir, Avp, Pkt, TPid, AppDict) ->
+    #diameter_packet{header = H, errors = Es}
+        = Pkt,
+    incr_result(Dir, Avp, H, Es, TPid, AppDict).
+
+%% incr_result/6
 
+incr_result(Dir, Avp, Hdr, Es, TPid, AppDict) ->
     Id = msg_id(Hdr, AppDict),
     %% Could be {relay, 0}, in which case the R-bit is redundant since
     %% only answers are being counted. Let it be however, so that the
     %% same tuple is in both send/recv and result code counters.
 
     %% Count incoming decode errors.
-    recv /= Dir orelse [] == Es orelse incr_error(Dir, Id, TPid, AppDict),
-
-    %% Exit on a missing result code.
-    T = rc_counter(MsgDict, Dir, Pkt),
-    T == false andalso ?LOGX(no_result_code, {MsgDict, Dir, Hdr}),
-    {Ctr, RC, Avp} = T,
-
-    %% Or on an inappropriate value.
-    is_result(RC, E, Dict0)
-        orelse ?LOGX(invalid_error_bit, {MsgDict, Dir, Hdr, Avp}),
+    send == Dir orelse [] == Es orelse incr_error(Dir, Id, TPid, AppDict),
 
+    Ctr = rcc(Avp),
     incr(TPid, {Id, Dir, Ctr}),
     Ctr.
 
@@ -1188,7 +1199,50 @@ is_result(RC, true, _) ->
 incr(TPid, Counter) ->
     diameter_stats:incr(Counter, TPid, 1).
 
-%% rc_counter/3
+%% rcc/1
+
+rcc(#diameter_avp{name = 'Result-Code' = Name, value = V}) ->
+    {Name, head(V)};
+
+rcc(#diameter_avp{name = 'Experimental-Result', value = V}) ->
+    head(V).
+
+%% head/1
+
+head([V|_]) ->
+    V;
+head(V) ->
+    V.
+
+%% rcv/1
+
+rcv(#diameter_avp{name = N, value = V}) ->
+    rcv(N, head(V)).
+
+%% rcv/2
+
+rcv('Experimental-Result', {_,_,N}) ->
+    N;
+
+rcv('Result-Code', N) ->
+    N.
+
+%% get_result/4
+
+%% Message sent as binary: no checks or counting.
+get_result(_, _, _, #diameter_packet{header = undefined}) ->
+    false;
+
+get_result(Dir, MsgDict, Dict0, Pkt) ->
+    Avp = get_result(MsgDict, msg(Dir, Pkt)),
+    Hdr = Pkt#diameter_packet.header,
+    %% Exit on a missing result code or inappropriate value.
+    Avp == false
+        andalso ?LOGX(no_result_code, {MsgDict, Dir, Hdr}),
+    E = Hdr#diameter_header.is_error,
+    is_result(rcv(Avp), E, Dict0)
+        orelse ?LOGX(invalid_error_bit, {MsgDict, Dir, Hdr, Avp}),
+    Avp.
 
 %% RFC 3588, 7.6:
 %%
@@ -1196,46 +1250,29 @@ incr(TPid, Counter) ->
 %%   applications MUST include either one Result-Code AVP or one
 %%   Experimental-Result AVP.
 
-rc_counter(Dict, Dir, #diameter_packet{header = H,
-                                       avps = As,
-                                       msg = Msg})
+%% msg/2
+
+msg(Dir, #diameter_packet{header = H,
+                          avps = As,
+                          msg = Msg})
   when Dir == recv;         %% decoded incoming
        Msg == undefined ->  %% relayed outgoing
-    rc_counter(Dict, [H|As]);
-
-rc_counter(Dict, _, #diameter_packet{msg = Msg}) ->
-    rc_counter(Dict, Msg).
-
-rc_counter(Dict, Msg) ->
-    rcc(get_result(Dict, Msg)).
+    [H|As];
 
-rcc(#diameter_avp{name = 'Result-Code' = Name, value = N} = A)
-  when is_integer(N) ->
-    {{Name, N}, N, A};
-
-rcc(#diameter_avp{name = 'Result-Code' = Name, value = [N|_]} = A)
-  when is_integer(N) ->
-    {{Name, N}, N, A};
-
-rcc(#diameter_avp{name = 'Experimental-Result', value = {_,_,N} = T} = A)
-  when is_integer(N) ->
-    {T, N, A};
-
-rcc(#diameter_avp{name = 'Experimental-Result', value = [{_,_,N} = T|_]} = A)
-  when is_integer(N) ->
-    {T, N, A};
-
-rcc(_) ->
-    false.
+msg(_, #diameter_packet{msg = Msg}) ->
+    Msg.
 
 %% get_result/2
 
 get_result(Dict, Msg) ->
     try
         [throw(A) || N <- ['Result-Code', 'Experimental-Result'],
-                     #diameter_avp{} = A <- [get_avp(Dict, N, Msg)]]
+                     #diameter_avp{} = A <- [get_avp(Dict, N, Msg)],
+                     is_integer(catch rcv(A))],
+        false
     catch
-        #diameter_avp{} = A -> A
+        #diameter_avp{} = A ->
+            A
     end.
 
 x(T) ->
@@ -1359,7 +1396,7 @@ make_opts([T | _], _, _, _, _, _) ->
 
 send_request({{TPid, _Caps} = TC, App}
              = Transport,
-             #{sequence := Mask}
+             #{sequence := Mask, traffic_counters := Count}
              = SvcOpts,
              Msg0,
              CallOpts,
@@ -1375,9 +1412,15 @@ send_request({{TPid, _Caps} = TC, App}
                             SvcOpts,
                             ReqPkt),
             eval_packet(EncPkt, Fs),
-            T = send_R(ReqPkt, EncPkt, Transport, CallOpts, Caller, SvcName),
+            T = send_R(ReqPkt,
+                       EncPkt,
+                       Transport,
+                       CallOpts,
+                       Caller,
+                       Count,
+                       SvcName),
             Ans = recv_answer(SvcName, App, CallOpts, T),
-            handle_answer(SvcName, SvcOpts, App, Ans);
+            handle_answer(SvcName, Count, SvcOpts, App, Ans);
         {discard, Reason} ->
             {error, Reason};
         discard ->
@@ -1520,6 +1563,7 @@ send_R(ReqPkt,
        {{TPid, _Caps} = TC, #diameter_app{dictionary = AppDict}},
        #options{timeout = Timeout},
        {Pid, Ref},
+       Count,
        SvcName) ->
     Req = #request{ref = Ref,
                    caller = Pid,
@@ -1527,7 +1571,7 @@ send_R(ReqPkt,
                    peer = TC,
                    packet = ReqPkt},
 
-    incr(send, EncPkt, TPid, AppDict),
+    Count andalso incr(send, EncPkt, TPid, AppDict),
     {TRef, MRef} = zend_requezt(TPid, EncPkt, Req, SvcName, Timeout),
     Pid ! Ref,  %% tell caller a send has been attempted
     {TRef, MRef, Req}.
@@ -1559,15 +1603,16 @@ failover(SvcName, App, Req, CallOpts) ->
                    CallOpts,
                    SvcName).
 
-%% handle_answer/4
+%% handle_answer/5
 
-handle_answer(SvcName, _, App, {error, Req, Reason}) ->
+handle_answer(SvcName, _, _, App, {error, Req, Reason}) ->
     #request{packet = Pkt,
              peer = {_TPid, _Caps} = TC}
         = Req,
     cb(App, handle_error, [Reason, msg(Pkt), SvcName, TC]);
 
 handle_answer(SvcName,
+              Count,
               SvcOpts,
               #diameter_app{id = Id,
                             dictionary = AppDict,
@@ -1581,43 +1626,50 @@ handle_answer(SvcName,
     #request{peer = {TPid, _}}
         = Req,
 
-    incr(recv, DecPkt, TPid, AppDict),
-
-    AnsPkt = try
-                 incr_result(recv, DecPkt, TPid, {MsgDict, AppDict, Dict0})
-             of
-                 _ -> DecPkt
-             catch
-                 exit: {no_result_code, _} ->
-                     %% RFC 6733 requires one of Result-Code or
-                     %% Experimental-Result, but the decode will have
-                     %% detected a missing AVP. If both are optional in
-                     %% the dictionary then this isn't a decode error:
-                     %% just continue on.
-                     DecPkt;
-                 exit: {invalid_error_bit, {_, _, _, Avp}} ->
-                     #diameter_packet{errors = Es}
-                         = DecPkt,
-                     E = {5004, Avp},
-                     DecPkt#diameter_packet{errors = [E|Es]}
-             end,
-
-    handle_answer(AnsPkt, SvcName, App, AE, Req).
+    answer(answer(DecPkt, TPid, MsgDict, AppDict, Dict0, Count),
+           SvcName,
+           App,
+           AE,
+           Req).
+
+%% answer/6
+
+answer(DecPkt, TPid, MsgDict, AppDict, Dict0, Count) ->
+    Count andalso incr(recv, DecPkt, TPid, AppDict),
+    try get_result(recv, MsgDict, Dict0, DecPkt) of
+        Avp ->
+            Count andalso false /= Avp
+                  andalso incr_result(recv, Avp, DecPkt, TPid, AppDict),
+            DecPkt
+    catch
+        exit: {no_result_code, _} ->
+            %% RFC 6733 requires one of Result-Code or
+            %% Experimental-Result, but the decode will have
+            %% detected a missing AVP. If both are optional in
+            %% the dictionary then this isn't a decode error:
+            %% just continue on.
+            DecPkt;
+        exit: {invalid_error_bit, {_, _, _, Avp}} ->
+            #diameter_packet{errors = Es}
+                = DecPkt,
+            E = {5004, Avp},
+            DecPkt#diameter_packet{errors = [E|Es]}
+    end.
 
-%% handle_answer/5
+%% answer/5
 
-handle_answer(#diameter_packet{errors = Es}
-              = Pkt,
-              SvcName,
-              App,
-              AE,
-              #request{peer = {_TPid, _Caps} = TC,
-                       packet = P})
+answer(#diameter_packet{errors = Es}
+       = Pkt,
+       SvcName,
+       App,
+       AE,
+       #request{peer = {_TPid, _Caps} = TC,
+                packet = P})
   when callback == AE;
        [] == Es ->
     cb(App, handle_answer, [Pkt, msg(P), SvcName, TC]);
 
-handle_answer(#diameter_packet{header = H}, SvcName, _, AE, _) ->
+answer(#diameter_packet{header = H}, SvcName, _, AE, _) ->
     handle_error(H, SvcName, AE).
 
 %% handle_error/3
@@ -1830,10 +1882,8 @@ get_destination(Dict, Msg) ->
     [str(get_avp_value(Dict, D, Msg)) || D <- ['Destination-Realm',
                                                'Destination-Host']].
 
-%% This is not entirely correct. The avp could have an arity 1, in
-%% which case an empty list is a DiameterIdentity of length 0 rather
-%% than the list of no values we treat it as by mapping to undefined.
-%% This behaviour is documented.
+%% A DiameterIdentity has length at least one, so an empty list is not
+%% a Realm/Host.
 str([]) ->
     undefined;
 str(T) ->
@@ -1859,29 +1909,27 @@ str(T) ->
 get_avp(?RELAY, Name, Msg) ->
     get_avp(?BASE, Name, Msg);
 
-%% Message as a header/avps list.
+%% Message is a header/avps list.
 get_avp(Dict, Name, [#diameter_header{} | Avps]) ->
     try
         {Code, _, VId} = Dict:avp_header(Name),
-        find_avp(Code, VId, Avps)
-    of
-        A ->
-            (avp_decode(Dict, Name, ungroup(A)))#diameter_avp{name = Name}
+        A = find_avp(Code, VId, Avps),
+        (avp_decode(Dict, Name, ungroup(A)))#diameter_avp{name = Name}
     catch
         error: _ ->
             undefined
     end;
 
-%% Outgoing message as a name/values list.
+%% Message as name/values list ...
 get_avp(_, Name, [_MsgName | Avps]) ->
-    case lists:keyfind(Name, 1, Avps) of
+    case find(Name, Avps) of
         {_, V} ->
             #diameter_avp{name = Name, value = V};
         _ ->
             undefined
     end;
 
-%% Message is typically a record but not necessarily.
+%% ... or record (but not necessarily).
 get_avp(Dict, Name, Rec) ->
     try
         #diameter_avp{name = Name, value = Dict:'#get-'(Name, Rec)}
@@ -1890,6 +1938,16 @@ get_avp(Dict, Name, Rec) ->
             undefined
     end.
 
+%% find/2
+
+find(Key, Map)
+  when is_map(Map) ->
+    maps:find(Key, Map);
+
+find(Key, List)
+  when is_list(List) ->
+    lists:keyfind(Key, 1, List).
+
 %% get_avp_value/3
 
 get_avp_value(Dict, Name, Msg) ->
@@ -1911,14 +1969,10 @@ ungroup(Avp) ->
 
 avp_decode(Dict, Name, #diameter_avp{value = undefined,
                                      data = Bin}
-                       = Avp) ->
-    try Dict:avp(decode, Bin, Name, decode_opts(Dict)) of
-        V ->
-            Avp#diameter_avp{value = V}
-    catch
-        error:_ ->
-            Avp
-    end;
+                       = Avp)
+  when is_binary(Bin) ->
+    V = Dict:avp(decode, Bin, Name, decode_opts(Dict)),
+    Avp#diameter_avp{value = V};
 avp_decode(_, _, #diameter_avp{} = Avp) ->
     Avp.
 
@@ -1933,7 +1987,8 @@ choose(false, _, X) -> X.
 
 %% Decode options sufficient for AVP extraction.
 decode_opts(Dict) ->
-    #{string_decode => false,
+    #{decode_format => record,
+      string_decode => false,
       strict_mbit => false,
       failed_avp => false,
       dictionary => Dict}.
diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index a63425d92a..b2172356ee 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -72,7 +72,9 @@
                      restrict := boolean(),
                      suspect := non_neg_integer(), %% OKAY -> SUSPECT
                      okay := non_neg_integer()},   %% REOPEN -> OKAY
-         codec :: #{string_decode := false,
+         codec :: #{decode_format := false,
+                    string_decode := false,
+                    strict_arities => diameter:strict_arities(),
                     strict_mbit := boolean(),
                     failed_avp := false,
                     rfc := 3588 | 6733,
@@ -135,7 +137,9 @@ i({Ack, T, Pid, {Opts,
     putr(restart, {T, Opts, Svc, SvcOpts}),  %% save seeing it in trace
     putr(dwr, dwr(Caps)),                    %%
     Nodes = restrict_nodes(Restrict),
-    CodecKeys = [string_decode,
+    CodecKeys = [decode_format,
+                 string_decode,
+                 strict_arities,
                  strict_mbit,
                  incoming_maxlen,
                  spawn_opt,
@@ -150,13 +154,15 @@ i({Ack, T, Pid, {Opts,
               receive_data = RecvData,
               dictionary = Dict0,
               config =
-                  maps:without(CodecKeys,
+                  maps:without([traffic_counters | CodecKeys],
                                config(SvcOpts#{restrict => restrict(Nodes),
                                                suspect => 1,
                                                okay => 3},
                                       Opts)),
-              codec = maps:with(CodecKeys, SvcOpts#{string_decode := false,
-                                                    ordered_encode => false})}.
+              codec = maps:with(CodecKeys -- [strict_arities],
+                                SvcOpts#{decode_format := false,
+                                         string_decode := false,
+                                         ordered_encode => false})}.
 
 wait(Ref, Pid) ->
     receive
diff --git a/lib/diameter/src/compiler/diameter_codegen.erl b/lib/diameter/src/compiler/diameter_codegen.erl
index f56e4a5249..4e6fe32d69 100644
--- a/lib/diameter/src/compiler/diameter_codegen.erl
+++ b/lib/diameter/src/compiler/diameter_codegen.erl
@@ -21,15 +21,14 @@
 -module(diameter_codegen).
 
 %%
-%% This module generates erl/hrl files for encode/decode modules
-%% from the orddict parsed from a dictionary file (.dia) by
-%% diameter_dict_util. The generated code is simple (one-liners),
-%% the generated functions being called by code included iin the
-%% generated modules from diameter_gen.hrl. The orddict itself is
-%% returned by dict/0 in the generated module and diameter_dict_util
-%% calls this function when importing dictionaries as a consequence
-%% of @inherits sections. That is, @inherits introduces a dependency
-%% on the beam file of another dictionary.
+%% This module generates erl/hrl files for encode/decode modules from
+%% the orddict parsed from a dictionary file by diameter_dict_util.
+%% The generated code is simple (one-liners), and is called from
+%% diameter_gen. The orddict itself is returned by dict/0 in the
+%% generated module and diameter_dict_util calls this function when
+%% importing dictionaries as a consequence of @inherits sections. That
+%% is, @inherits introduces a dependency on the beam file of another
+%% dictionary.
 %%
 
 -export([from_dict/4,
diff --git a/lib/diameter/src/compiler/diameter_exprecs.erl b/lib/diameter/src/compiler/diameter_exprecs.erl
index 9a0cb6baf2..143dede037 100644
--- a/lib/diameter/src/compiler/diameter_exprecs.erl
+++ b/lib/diameter/src/compiler/diameter_exprecs.erl
@@ -110,9 +110,9 @@
 %% parse_transform/2
 
 parse_transform(Forms, _Options) ->
-    Rs = [R || {attribute, _, record, R} <- Forms],
-    Es = lists:append([E || {attribute, _, export_records, E} <- Forms]),
     {H,T} = lists:splitwith(fun is_head/1, Forms),
+    Rs = [R || {attribute, _, record, R} <- H],
+    Es = lists:append([E || {attribute, _, export_records, E} <- H]),
     H ++ [a_export(Es) | f_accessors(Es, Rs)] ++ T.
 
 is_head(T) ->
diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index aa09a261a3..5d7bca059a 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -87,8 +87,7 @@
          module :: module() | undefined}).
 
 -type length() :: 0..16#FFFFFF. %% message length from Diameter header
--type size()   :: non_neg_integer().  %% accumulated binary size
--type frag()   :: {length(), size(), binary(), list(binary())}
+-type frag()   :: maybe_improper_list(length(), binary())
                 | binary().
 
 -type connect_option() :: {raddr, inet:ip_address()}
@@ -599,11 +598,12 @@ t(T,S) ->
 
 %% Incoming packets.
 transition({P, Sock, Bin}, #transport{socket = Sock,
-                                      ssl = B}
+                                      ssl = B,
+                                      frag = Frag}
                            = S)
   when P == ssl, true == B;
        P == tcp ->
-    recv(Bin, S#transport{active = false});
+    recv(acc(Frag, Bin), S);
 
 %% Capabilties exchange has decided on whether or not to run over TLS.
 transition({diameter, {tls, Ref, Type, B}}, #transport{parent = Pid}
@@ -720,86 +720,77 @@ tls(accept, Sock, Opts) ->
 %% using Nagle.
 
 %% Receive packets until a full message is received,
-recv(Bin, #transport{frag = Head} = S) ->
-    case rcv(Head, Bin) of
-        {Msg, B} ->         %% have a complete message ...
-            message(recv, Msg, S#transport{frag = B});
-        Frag ->              %% read more on the socket
-            start_fragment_timer(setopts(S#transport{frag = Frag,
-                                                     flush = false}))
-    end.
 
-%% rcv/2
+recv({Msg, Rest}, S) ->  %% have a complete message ...
+    recv(acc(Rest), message(recv, Msg, S));
+
+recv(Frag, #transport{recv = B,
+                      socket = Sock,
+                      module = M}
+           = S) ->       %% or not
+    B andalso setopts(M, Sock),
+    start_fragment_timer(S#transport{frag = Frag,
+                                     flush = false,
+                                     active = B}).
 
-%% No previous fragment.
-rcv(<<>>, Bin) ->
-    rcv(Bin);
+%% acc/2
 
-%% Not even the first four bytes of the header.
-rcv(Head, Bin)
-  when is_binary(Head) ->
-    rcv(<<Head/binary, Bin/binary>>);
+%% Know how many bytes to extract.
+acc([Len | Acc], Bin) ->
+    acc1(Len, <<Acc/binary, Bin/binary>>);
 
-%% Or enough to know how many bytes to extract.
-rcv({Len, N, Head, Acc}, Bin) ->
-    rcv(Len, N + size(Bin), Head, [Bin | Acc]).
+%% Or not.
+acc(Head, Bin) ->
+    acc(<<Head/binary, Bin/binary>>).
 
-%% rcv/4
+%% acc1/3
 
 %% Extract a message for which we have all bytes.
-rcv(Len, N, Head, Acc)
-  when Len =< N ->
-    recv1(Len, bin(Head, Acc));
+acc1(Len, Bin)
+  when Len =< byte_size(Bin) ->
+    split_binary(Bin, Len);
 
 %% Wait for more packets.
-rcv(Len, N, Head, Acc) ->
-    {Len, N, Head, Acc}.
-
-%% rcv/1
-
-%% Nothing left.
-rcv(<<>> = Bin) ->
-    Bin;
-
-%% The Message Length isn't even sufficient for a header. Chances are
-%% things will go south from here but if we're lucky then the bytes we
-%% have extend to an intended message boundary and we can recover by
-%% simply receiving them. Make it so.
-rcv(<<_:1/binary, Len:24, _/binary>> = Bin)
-  when Len < 20 ->
-    {Bin, <<>>};
-
-%% Enough bytes to extract a message.
-rcv(<<_:1/binary, Len:24, _/binary>> = Bin)
-  when Len =< size(Bin) ->
-    recv1(Len, Bin);
-
-%% Or not: wait for more packets.
-rcv(<<_:1/binary, Len:24, _/binary>> = Head) ->
-    {Len, size(Head), Head, []};
+acc1(Len, Bin) ->
+    [Len | Bin].
+
+%% acc/1
+
+%% Don't match on Bin since this results in it being copied at the
+%% next append according to the Efficiency Guide. This is also the
+%% reason that the Len is extracted and maintained when accumulating
+%% messages. The simplest implementation is just to accumulate a
+%% binary and match <<_, Len:24, _/binary>> each time the length is
+%% required, but the performance of this decays quadratically with the
+%% message length, since the binary is then copied with each append of
+%% additional bytes from gen_tcp.
+
+acc(Bin)
+  when 3 < byte_size(Bin) ->
+    {Head, _} = split_binary(Bin, 4),
+    [_,A,B,C] = binary_to_list(Head),
+    Len = (A bsl 16) bor (B bsl 8) bor C,
+    if Len < 20 ->
+            %% Message length isn't sufficient for a Diameter Header.
+            %% Chances are things will go south from here but if we're
+            %% lucky then the bytes we have extend to an intended
+            %% message boundary and we can recover by simply receiving
+            %% them. Make it so.
+            {Bin, <<>>};
+       true ->
+            acc1(Len, Bin)
+    end;
 
 %% Not even 4 bytes yet.
-rcv(Head) ->
-    Head.
-
-%% recv1/2
-
-recv1(Len, Bin) ->
-    <<Msg:Len/binary, Rest/binary>> = Bin,
-    {Msg, Rest}.
-
-%% bin/2
-
-bin(Head, Acc) ->
-    list_to_binary([Head | lists:reverse(Acc)]).
+acc(Bin) ->
+    Bin.
 
 %% bin/1
 
-bin({_, _, Head, Acc}) ->
-    bin(Head, Acc);
+bin([_ | Bin]) ->
+    Bin;
 
-bin(Bin)
-  when is_binary(Bin) ->
+bin(Bin) ->
     Bin.
 
 %% flush/1
@@ -911,14 +902,20 @@ setopts(#transport{socket = Sock,
                    module = M}
         = S)
   when B, not A ->
-    case setopts(M, Sock, [{active, once}]) of
-        ok -> S#transport{active = true};
-        X  -> x({setopts, Sock, M, X})  %% possibly on peer disconnect
-    end;
+    setopts(M, Sock),
+    S#transport{active = true};
 
 setopts(S) ->
     S.
 
+%% setopts/2
+
+setopts(M, Sock) ->
+    case setopts(M, Sock, [{active, once}]) of
+        ok -> ok;
+        X  -> x({setopts, Sock, M, X})  %% possibly on peer disconnect
+    end.
+
 %% portnr/2
 
 portnr(gen_tcp, Sock) ->
@@ -988,7 +985,7 @@ message(ack, _, #transport{message_cb = false} = S) ->
     S;
 
 message(Dir, Msg, #transport{message_cb = CB} = S) ->
-    recv(<<>>, actions(cb(CB, Dir, Msg), Dir, S)).
+    setopts(actions(cb(CB, Dir, Msg), Dir, S)).
 
 %% actions/3
 
diff --git a/lib/diameter/test/diameter_codec_SUITE.erl b/lib/diameter/test/diameter_codec_SUITE.erl
index 9f08f49f9f..c79b642c09 100644
--- a/lib/diameter/test/diameter_codec_SUITE.erl
+++ b/lib/diameter/test/diameter_codec_SUITE.erl
@@ -292,6 +292,7 @@ recode(Msg, Dict) ->
 
 opts(Mod) ->
     #{dictionary => Mod,
+      decode_format => record,
       string_decode => false,
       strict_mbit => true,
       rfc => 6733,
diff --git a/lib/diameter/test/diameter_codec_SUITE_data/diameter_test_unknown.erl b/lib/diameter/test/diameter_codec_SUITE_data/diameter_test_unknown.erl
index 700910878c..735339ebb9 100644
--- a/lib/diameter/test/diameter_codec_SUITE_data/diameter_test_unknown.erl
+++ b/lib/diameter/test/diameter_codec_SUITE_data/diameter_test_unknown.erl
@@ -78,6 +78,7 @@ dec('BR', #diameter_packet
 
 opts(Mod) ->
     #{dictionary => Mod,
+      decode_format => record,
       string_decode => true,
       strict_mbit => true,
       rfc => 6733,
diff --git a/lib/diameter/test/diameter_codec_test.erl b/lib/diameter/test/diameter_codec_test.erl
index b548f85cb8..22fb0550ea 100644
--- a/lib/diameter/test/diameter_codec_test.erl
+++ b/lib/diameter/test/diameter_codec_test.erl
@@ -219,7 +219,8 @@ opts(Mod) ->
               dictionary => Mod}.
 
 opts() ->
-    #{string_decode => true,
+    #{decode_format => record,
+      string_decode => true,
       strict_mbit => true,
       rfc => 6733,
       failed_avp => false}.
diff --git a/lib/diameter/test/diameter_traffic_SUITE.erl b/lib/diameter/test/diameter_traffic_SUITE.erl
index 84b41f14b7..8b0ce9710a 100644
--- a/lib/diameter/test/diameter_traffic_SUITE.erl
+++ b/lib/diameter/test/diameter_traffic_SUITE.erl
@@ -27,15 +27,18 @@
 -export([suite/0,
          all/0,
          groups/0,
+         init_per_suite/0,
          init_per_suite/1,
          end_per_suite/1,
+         init_per_group/1,
          init_per_group/2,
          end_per_group/2,
          init_per_testcase/2,
          end_per_testcase/2]).
 
 %% testcases
--export([start/1,
+-export([rfc4005/1,
+         start/1,
          start_services/1,
          add_transports/1,
          result_codes/1,
@@ -63,6 +66,7 @@
          send_invalid_reject/1,
          send_unexpected_mandatory_decode/1,
          send_unexpected_mandatory/1,
+         send_too_many/1,
          send_long/1,
          send_maxlen/1,
          send_nopeer/1,
@@ -98,14 +102,14 @@
          stop/1]).
 
 %% diameter callbacks
--export([peer_up/3,
-         peer_down/3,
-         pick_peer/6, pick_peer/7,
-         prepare_request/5, prepare_request/6,
-         prepare_retransmit/5,
-         handle_answer/6, handle_answer/7,
-         handle_error/6,
-         handle_request/3]).
+-export([peer_up/4,
+         peer_down/4,
+         pick_peer/7, pick_peer/8,
+         prepare_request/6, prepare_request/7,
+         prepare_retransmit/6,
+         handle_answer/7, handle_answer/8,
+         handle_error/7,
+         handle_request/4]).
 
 %% diameter_{tcp,sctp} callbacks
 -export([message/3]).
@@ -119,13 +123,21 @@
 
 %% ===========================================================================
 
+%% Fraction of shuffle/parallel groups to randomly skip.
+-define(SKIP, 0.25).
+
+%% Positive number of testcases from which to select (randomly) from
+%% tc(), the list of testcases to run, or [] to run all. The random
+%% selection is to limit the time it takes for the suite to run.
+-define(LIMIT, #{tcp => 42, sctp => 5}).
+
 -define(util, diameter_util).
 
 -define(A, list_to_atom).
 -define(L, atom_to_list).
 
 %% Don't use is_record/2 since dictionary hrl's aren't included.
-%% (Since they define conflicting reqcords with the same names.)
+%% (Since they define conflicting records with the same names.)
 -define(is_record(Rec, Name), (Name == element(1, Rec))).
 
 -define(ADDR, {127,0,0,1}).
@@ -138,14 +150,14 @@
 %% Sequence mask for End-to-End and Hop-by-Hop identifiers.
 -define(CLIENT_MASK, {1,26}).  %% 1 in top 6 bits
 
-%% How to construct messages, as record or list.
--define(ENCODINGS, [list, record]).
+%% How to construct outgoing messages.
+-define(ENCODINGS, [list, record, map]).
 
-%% How to send answers, in a diameter_packet or not.
--define(CONTAINERS, [pkt, msg]).
+%% How to decode incoming messages.
+-define(DECODINGS, [record, false, map, list, record_from_map]).
 
-%% Which common dictionary to use in the clients.
--define(RFCS, [rfc3588, rfc6733]).
+%% Which dictionary to use in the clients.
+-define(RFCS, [rfc3588, rfc6733, rfc4005]).
 
 %% Whether to decode stringish Diameter types to strings, or leave
 %% them as binary.
@@ -163,13 +175,12 @@
 -record(group,
         {transport,
          strings,
+         encoding,
          client_service,
-         client_encoding,
-         client_dict0,
+         client_dict,
          client_sender,
          server_service,
-         server_encoding,
-         server_container,
+         server_decoding,
          server_sender,
          server_throttle}).
 
@@ -182,34 +193,36 @@
 
 %% A common match when receiving answers in a client.
 -define(answer_message(SessionId, ResultCode),
-        ['answer-message',
-         {'Session-Id', SessionId},
-         {'Origin-Host', _},
-         {'Origin-Realm', _},
-         {'Result-Code', ResultCode}
-         | _]).
+        ['answer-message' | #{'Session-Id' := SessionId,
+                              'Origin-Host' := _,
+                              'Origin-Realm' := _,
+                              'Result-Code' := ResultCode}]).
 -define(answer_message(ResultCode),
-        ?answer_message(_, ResultCode)).
+        ['answer-message' | #{'Origin-Host' := _,
+                              'Origin-Realm' := _,
+                              'Result-Code' := ResultCode}]).
 
 %% Config for diameter:start_service/2.
--define(SERVICE(Name, Decode),
+-define(SERVICE(Name, Grp),
         [{'Origin-Host', Name ++ "." ++ ?REALM},
          {'Origin-Realm', ?REALM},
          {'Host-IP-Address', [?ADDR]},
          {'Vendor-Id', 12345},
          {'Product-Name', "OTP/diameter"},
-         {'Auth-Application-Id', [?DIAMETER_APP_ID_COMMON]},
-         {'Acct-Application-Id', [?DIAMETER_APP_ID_ACCOUNTING]},
+         {'Auth-Application-Id', [0]},  %% common messages
+         {'Acct-Application-Id', [3]},  %% base accounting
          {restrict_connections, false},
-         {string_decode, Decode},
+         {string_decode, Grp#group.strings},
          {incoming_maxlen, 1 bsl 21}
          | [{application, [{dictionary, D},
-                           {module, ?MODULE},
+                           {module, [?MODULE, Grp]},
                            {answer_errors, callback}]}
             || D <- [diameter_gen_base_rfc3588,
                      diameter_gen_base_accounting,
                      diameter_gen_base_rfc6733,
-                     diameter_gen_acct_rfc6733]]]).
+                     diameter_gen_acct_rfc6733,
+                     nas4005],
+               D /= nas4005 orelse have_nas()]]).
 
 -define(SUCCESS,
         ?'DIAMETER_BASE_RESULT-CODE_SUCCESS').
@@ -227,6 +240,8 @@
         ?'DIAMETER_BASE_RESULT-CODE_AVP_UNSUPPORTED').
 -define(UNSUPPORTED_VERSION,
         ?'DIAMETER_BASE_RESULT-CODE_UNSUPPORTED_VERSION').
+-define(TOO_MANY,
+        ?'DIAMETER_BASE_RESULT-CODE_AVP_OCCURS_TOO_MANY_TIMES').
 -define(REALM_NOT_SERVED,
         ?'DIAMETER_BASE_RESULT-CODE_REALM_NOT_SERVED').
 -define(UNABLE_TO_DELIVER,
@@ -254,64 +269,75 @@ suite() ->
     [{timetrap, {seconds, 10}}].
 
 all() ->
-    [start, result_codes, {group, traffic}, empty, stop].
+    [rfc4005, start, result_codes, {group, traffic}, empty, stop].
+
+%% Redefine this to run one or more groups for debugging purposes.
+-define(GROUPS, []).
+%-define(GROUPS, [[tcp,rfc6733,record,map,false,false,false,false]]).
 
+%% Issues with gen_sctp sporadically cause huge numbers of failed
+%% testcases when running testcases in parallel.
 groups() ->
-    [{P, [P], Ts} || Ts <- [tc(tc())], P <- [shuffle, parallel]]
+    Names = names(),
+    [{P, [P], Ts} || Ts <- [tc()], P <- [shuffle, parallel]]
         ++
-        [{?util:name([T,R,D,A,C,S,SS,ST,CS]),
-          [],
-          [{group, if S -> shuffle; not S -> parallel end}]}
-         || T <- ?TRANSPORTS,
-            R <- ?ENCODINGS,
-            D <- ?RFCS,
-            A <- ?ENCODINGS,
-            C <- ?CONTAINERS,
-            S <- ?STRING_DECODES,
-            SS <- ?SENDERS,
-            ST <- ?CALLBACKS,
-            CS <- ?SENDERS]
+        [{?util:name(N), [], [{group, if T == sctp; S -> shuffle;
+                                         true         -> parallel end}]}
+         || [T,_,_,_,S|_] = N <- Names]
         ++
-        [{T, [], groups([[T,R,D,A,C,S,SS,ST,CS]
-                         || R <- ?ENCODINGS,
-                            D <- ?RFCS,
-                            A <- ?ENCODINGS,
-                            C <- ?CONTAINERS,
-                            S <- ?STRING_DECODES,
-                            SS <- ?SENDERS,
-                            ST <- ?CALLBACKS,
-                            CS <- ?SENDERS,
-                            SS orelse CS])}  %% avoid deadlock
+        [{T, [], [{group, ?util:name(N)} || N <- names(Names, ?GROUPS),
+                                            T == hd(N)]}
          || T <- ?TRANSPORTS]
         ++
         [{traffic, [], [{group, T} || T <- ?TRANSPORTS]}].
 
-%groups(_) ->  %% debug
-%    Name = [sctp,record,rfc6733,record,pkt,false,false,false,false],
-%    [{group, ?util:name(Name)}];
-groups(Names) ->
-    [{group, ?util:name(L)} || L <- Names].
+names() ->
+    [[T,R,E,D,S,ST,SS,CS] || T  <- ?TRANSPORTS,
+                             R  <- ?RFCS,
+                             E  <- ?ENCODINGS,
+                             D  <- ?DECODINGS,
+                             S  <- ?STRING_DECODES,
+                             ST <- ?CALLBACKS,
+                             SS <- ?SENDERS,
+                             CS <- ?SENDERS].
 
-%tc([N|_]) ->  %% debug
-%    [N];
-tc(L) ->
-    L.
+names(Names, []) ->
+    [N || N <- Names,
+          [CS,SS|_] <- [lists:reverse(N)],
+          SS orelse CS];  %% avoid deadlock
+
+names(_, Names) ->
+    Names.
 
 %% --------------------
 
+init_per_suite() ->
+    [{timetrap, {seconds, 60}}].
+
 init_per_suite(Config) ->
-    [{sctp, ?util:have_sctp()} | Config].
+    [{rfc4005, compile_and_load()}, {sctp, ?util:have_sctp()} | Config].
 
 end_per_suite(_Config) ->
+    code:delete(nas4005),
+    code:purge(nas4005),
     ok.
 
 %% --------------------
 
+init_per_group(_) ->
+    [{timetrap, {seconds, 30}}].
+
 init_per_group(Name, Config)
   when Name == shuffle;
        Name == parallel ->
-    start_services(Config),
-    add_transports(Config);
+    case rand:uniform() < ?SKIP of
+        true ->
+            {skip, random};
+        false ->
+            start_services(Config),
+            add_transports(Config),
+            replace({sleep, Name == parallel}, Config)
+    end;
 
 init_per_group(sctp = Name, Config) ->
     {_, Sctp} = lists:keyfind(Name, 1, Config),
@@ -322,24 +348,22 @@ init_per_group(sctp = Name, Config) ->
     end;
 
 init_per_group(Name, Config) ->
+    Nas = proplists:get_value(rfc4005, Config, false),
     case ?util:name(Name) of
-        [T,R,D,A,C,S,SS,ST,CS] ->
+        [_,R,_,_,_,_,_,_] when R == rfc4005, true /= Nas ->
+            {skip, rfc4005};
+        [T,R,E,D,S,ST,SS,CS] ->
             G = #group{transport = T,
                        strings = S,
+                       encoding = E,
                        client_service = [$C|?util:unique_string()],
-                       client_encoding = R,
-                       client_dict0 = dict0(D),
+                       client_dict = appdict(R),
                        client_sender = CS,
                        server_service = [$S|?util:unique_string()],
-                       server_encoding = A,
-                       server_container = C,
+                       server_decoding = D,
                        server_sender = SS,
                        server_throttle = ST},
-            %% Limit the number of testcase, since the number of
-            %% groups is large.
-            All = ?util:scramble(tc()),
-            TCs = lists:sublist(All, rand:uniform(32)),
-            [{group, G}, {runlist, TCs} | Config];
+            replace([{group, G}, {runlist, select(T)}], Config);
         _ ->
             Config
     end.
@@ -353,6 +377,14 @@ end_per_group(Name, Config)
 end_per_group(_, _) ->
     ok.
 
+select(T) ->
+    try maps:get(T, ?LIMIT) of
+        N ->
+            lists:sublist(?util:scramble(tc()), max(5, rand:uniform(N)))
+    catch
+        error:_ -> ?LIMIT
+    end.
+
 %% --------------------
 
 %% Skip testcases that can reasonably fail under SCTP.
@@ -368,12 +400,23 @@ init_per_testcase(Name, Config) ->
         _ when not Run ->
             {skip, random};
         _ ->
+            proplists:get_value(sleep, Config, false)
+                andalso timer:sleep(rand:uniform(200)),
             [{testcase, Name} | Config]
     end.
 
 end_per_testcase(_, _) ->
     ok.
 
+%% replace/2
+
+replace(Pairs, Config)
+  when is_list(Pairs) ->
+    lists:foldl(fun replace/2, Config, Pairs);
+
+replace({Key, _} = T, Config) ->
+    [T | lists:keydelete(Key, 1, Config)].
+
 %% --------------------
 
 %% Testcases to run when services are started and connections
@@ -403,6 +446,7 @@ tc() ->
      send_invalid_reject,
      send_unexpected_mandatory_decode,
      send_unexpected_mandatory,
+     send_too_many,
      send_long,
      send_maxlen,
      send_nopeer,
@@ -440,16 +484,25 @@ start(_Config) ->
     ok = diameter:start().
 
 start_services(Config) ->
-    #group{strings = S,
-           client_service = CN,
-           server_service = SN}
+    #group{client_service = CN,
+           server_service = SN,
+           server_decoding = SD}
+        = Grp
         = group(Config),
-    ok = diameter:start_service(SN, ?SERVICE(SN, S)),
-    ok = diameter:start_service(CN, [{sequence, ?CLIENT_MASK}
-                                     | ?SERVICE(CN, S)]).
+    ok = diameter:start_service(SN, [{traffic_counters, bool()},
+                                     {decode_format, SD}
+                                     | ?SERVICE(SN, Grp)]),
+    ok = diameter:start_service(CN, [{traffic_counters, bool()},
+                                     {sequence, ?CLIENT_MASK},
+                                     {strict_arities, decode}
+                                     | ?SERVICE(CN, Grp)]).
+
+bool() ->
+    0.5 =< rand:uniform().
 
 add_transports(Config) ->
     #group{transport = T,
+           encoding = E,
            client_service = CN,
            client_sender = CS,
            server_service = SN,
@@ -459,30 +512,46 @@ add_transports(Config) ->
     LRef = ?util:listen(SN,
                         [T,
                          {sender, SS},
-                         {message_cb, ST andalso {?MODULE, message, [4]}}
+                         {message_cb, ST andalso {?MODULE, message, [0]}}
                          | [{packet, hd(?util:scramble([false, raw]))}
                             || T == sctp andalso CS]],
                         [{capabilities_cb, fun capx/2},
-                         {pool_size, 8},
-                         {applications, apps(rfc3588)}]
+                         {pool_size, 8}
+                         | server_apps()]
                         ++ [{spawn_opt, {erlang, spawn, []}} || CS]),
     Cs = [?util:connect(CN,
                         [T, {sender, CS}],
                         LRef,
-                        [{id, Id},
-                         {capabilities, [{'Origin-State-Id', origin(Id)}]},
-                         {applications, apps(D)}])
-          || A <- ?ENCODINGS,
-             C <- ?CONTAINERS,
-             D <- ?RFCS,
-             Id <- [{A,C}]],
-    %% The server uses the client's Origin-State-Id to decide how to
-    %% answer.
+                        [{id, Id}
+                         | client_apps(R, [{'Origin-State-Id', origin(Id)}])])
+          || D <- ?DECODINGS,  %% for multiple candidate peers
+             R <- ?RFCS,
+             R /= rfc4005 orelse have_nas(),
+             Id <- [{D,E}]],
     ?util:write_priv(Config, "transport", [LRef | Cs]).
 
-apps(D0) ->
-    D = dict0(D0),
-    [acct(D), D].
+server_apps() ->
+    B = have_nas(),
+    [{applications, [diameter_gen_base_rfc3588,
+                     diameter_gen_base_accounting]
+                    ++ [nas4005 || B]},
+     {capabilities, [{'Auth-Application-Id', [0] ++ [1 || B]}, %% common, NAS
+                     {'Acct-Application-Id', [3]}]}].          %% accounting
+
+client_apps(D, Caps) ->
+    if D == rfc4005 ->
+            [{applications, [nas4005]},
+             {capabilities, [{'Auth-Application-Id', [1]},     %% NAS
+                             {'Acct-Application-Id', []}
+                             | Caps]}];
+       true ->
+            D0 = dict0(D),
+            [{applications, [acct(D0), D0]},
+             {capabilities, Caps}]
+    end.
+
+have_nas() ->
+    false /= code:is_loaded(nas4005).
 
 remove_transports(Config) ->
     #group{client_service = CN,
@@ -515,9 +584,16 @@ capx(_, #diameter_caps{origin_host = {OH,DH}}) ->
 
 %% ===========================================================================
 
+%% Fail only this testcase if the RFC 4005 dictionary hasn't been
+%% successfully compiled and loaded.
+rfc4005(Config) ->
+    true = proplists:get_value(rfc4005, Config).
+
 %% Ensure that result codes have the expected values.
 result_codes(_Config) ->
-    {2001, 3001, 3002, 3003, 3004, 3007, 3008, 3009, 5001, 5011, 5014}
+    {2001,
+     3001, 3002, 3003, 3004, 3007, 3008, 3009,
+     5001, 5009, 5011, 5014}
         = {?SUCCESS,
            ?COMMAND_UNSUPPORTED,
            ?UNABLE_TO_DELIVER,
@@ -527,6 +603,7 @@ result_codes(_Config) ->
            ?INVALID_HDR_BITS,
            ?INVALID_AVP_BITS,
            ?AVP_UNSUPPORTED,
+           ?TOO_MANY,
            ?UNSUPPORTED_VERSION,
            ?INVALID_AVP_LENGTH}.
 
@@ -535,7 +612,8 @@ send_ok(Config) ->
     Req = ['ACR', {'Accounting-Record-Type', ?EVENT_RECORD},
                   {'Accounting-Record-Number', 1}],
 
-    ['ACA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['ACA' | #{'Result-Code' := ?SUCCESS,
+               'Session-Id' := _}]
         = call(Config, Req).
 
 %% Send an accounting ACR that the server answers badly to.
@@ -551,7 +629,8 @@ send_eval(Config) ->
     Req = ['ACR', {'Accounting-Record-Type', ?EVENT_RECORD},
                   {'Accounting-Record-Number', 3}],
 
-    ['ACA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['ACA' | #{'Result-Code' := ?SUCCESS,
+               'Session-Id' := _}]
         = call(Config, Req).
 
 %% Send an accounting ACR that the server tries to answer with an
@@ -577,7 +656,7 @@ send_protocol_error(Config) ->
 send_experimental_result(Config) ->
     Req = ['ACR', {'Accounting-Record-Type', ?EVENT_RECORD},
                   {'Accounting-Record-Number', 5}],
-    ['ACA', {'Session-Id', _} | _]
+    ['ACA' | #{'Session-Id' := _}]
         = call(Config, Req).
 
 %% Send an ASR with an arbitrary non-mandatory AVP and expect success
@@ -585,11 +664,11 @@ send_experimental_result(Config) ->
 send_arbitrary(Config) ->
     Req = ['ASR', {'AVP', [#diameter_avp{name = 'Product-Name',
                                          value = "XXX"}]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | Avps]
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS,
+               'AVP' := [#diameter_avp{name = 'Product-Name',
+                                       value = V}]}]
         = call(Config, Req),
-    {'AVP', [#diameter_avp{name = 'Product-Name',
-                           value = V}]}
-        = lists:last(Avps),
     "XXX" = string(V, Config).
 
 %% Send an unknown AVP (to some client) and check that it comes back.
@@ -597,12 +676,12 @@ send_unknown(Config) ->
     Req = ['ASR', {'AVP', [#diameter_avp{code = 999,
                                          is_mandatory = false,
                                          data = <<17>>}]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | Avps]
-        = call(Config, Req),
-    {'AVP', [#diameter_avp{code = 999,
-                           is_mandatory = false,
-                           data = <<17>>}]}
-        = lists:last(Avps).
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS,
+               'AVP' := [#diameter_avp{code = 999,
+                                       is_mandatory = false,
+                                       data = <<17>>}]}]
+        = call(Config, Req).
 
 %% Ditto, and point the AVP length past the end of the message. Expect
 %% 5014.
@@ -613,28 +692,28 @@ send_unknown_short(Config, M, RC) ->
     Req = ['ASR', {'AVP', [#diameter_avp{code = 999,
                                          is_mandatory = M,
                                          data = <<17>>}]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', RC} | Avps]
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := RC,
+               'Failed-AVP' := Avps}]
         = call(Config, Req),
-    [#'diameter_base_Failed-AVP'{'AVP' = As}]
-        = proplists:get_value('Failed-AVP', Avps),
-    [#diameter_avp{code = 999,
-                   is_mandatory = M,
-                   data = <<17, _/binary>>}]  %% extra bits from padding
-        = As.
+    [[#diameter_avp{code = 999,
+                    is_mandatory = M,
+                    data = <<17, _/binary>>}]] %% extra bits from padding
+        = failed_avps(Avps, Config).
 
 %% Ditto but set the M flag.
 send_unknown_mandatory(Config) ->
     Req = ['ASR', {'AVP', [#diameter_avp{code = 999,
                                          is_mandatory = true,
                                          data = <<17>>}]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', ?AVP_UNSUPPORTED} | Avps]
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?AVP_UNSUPPORTED,
+               'Failed-AVP' := Avps}]
         = call(Config, Req),
-    [#'diameter_base_Failed-AVP'{'AVP' = As}]
-        = proplists:get_value('Failed-AVP', Avps),
-    [#diameter_avp{code = 999,
-                   is_mandatory = true,
-                   data = <<17>>}]
-        = As.
+    [[#diameter_avp{code = 999,
+                    is_mandatory = true,
+                    data = <<17>>}]]
+        = failed_avps(Avps, Config).
 
 %% Ditto, and point the AVP length past the end of the message. Expect
 %% 5014 instead of 5001.
@@ -647,15 +726,27 @@ send_unexpected_mandatory_decode(Config) ->
     Req = ['ASR', {'AVP', [#diameter_avp{code = 27,  %% Session-Timeout
                                          is_mandatory = true,
                                          data = <<12:32>>}]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', ?AVP_UNSUPPORTED} | Avps]
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?AVP_UNSUPPORTED,
+               'Failed-AVP' := Avps}]
         = call(Config, Req),
-    [#'diameter_base_Failed-AVP'{'AVP' = As}]
-        = proplists:get_value('Failed-AVP', Avps),
-    [#diameter_avp{code = 27,
-                   is_mandatory = true,
-                   value = 12,
-                   data = <<12:32>>}]
-        = As.
+    [[#diameter_avp{code = 27,
+                    is_mandatory = true,
+                    value = 12,
+                    data = <<12:32>>}]]
+        = failed_avps(Avps, Config).
+
+%% Try to two Auth-Application-Id in ASR expect 5009.
+send_too_many(Config) ->
+    Req = ['ASR', {'Auth-Application-Id', [?APP_ID, 44]}],
+
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?TOO_MANY,
+               'Failed-AVP' := Avps}]
+        = call(Config, Req),
+    [[#diameter_avp{name = 'Auth-Application-Id',
+                    value = 44}]]
+        = failed_avps(Avps, Config).
 
 %% Send an containing a faulty Grouped AVP (empty Proxy-Host in
 %% Proxy-Info) and expect that only the faulty AVP is sent in
@@ -665,15 +756,13 @@ send_unexpected_mandatory_decode(Config) ->
 send_grouped_error(Config) ->
     Req = ['ASR', {'Proxy-Info', [[{'Proxy-Host', "abcd"},
                                    {'Proxy-State', ""}]]}],
-    ['ASA', {'Session-Id', _}, {'Result-Code', ?INVALID_AVP_LENGTH} | Avps]
+    ['ASA' | #{'Session-Id' := _,
+               'Result-Code' := ?INVALID_AVP_LENGTH,
+               'Failed-AVP' := Avps}]
         = call(Config, Req),
-    [#'diameter_base_Failed-AVP'{'AVP' = As}]
-        = proplists:get_value('Failed-AVP', Avps),
-    [#diameter_avp{name = 'Proxy-Info',
-                   value = #'diameter_base_Proxy-Info'
-                            {'Proxy-Host' = Empty,
-                             'Proxy-State' = undefined}}]
-        = As,
+    [[#diameter_avp{name = 'Proxy-Info', value = V}]]
+        = failed_avps(Avps, Config),
+    {Empty, undefined, []} = proxy_info(V, Config),
     <<0>> = iolist_to_binary(Empty).
 
 %% Send an STR that the server ignores.
@@ -702,7 +791,8 @@ send_error_bit(Config) ->
 %% Send a bad version and check that we get 5011.
 send_unsupported_version(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
-    ['STA', {'Session-Id', _}, {'Result-Code', ?UNSUPPORTED_VERSION} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?UNSUPPORTED_VERSION}]
         = call(Config, Req).
 
 %% Send a request containing an AVP length > data size.
@@ -722,17 +812,13 @@ send_zero_avp_length(Config) ->
 send_invalid_avp_length(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
 
-    ['STA', {'Session-Id', _},
-            {'Result-Code', ?INVALID_AVP_LENGTH},
-            {'Origin-Host', _},
-            {'Origin-Realm', _},
-            {'User-Name', _},
-            {'Class', _},
-            {'Error-Message', _},
-            {'Error-Reporting-Host', _},
-            {'Failed-AVP', [#'diameter_base_Failed-AVP'{'AVP' = [_]}]}
-          | _]
-        = call(Config, Req).
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?INVALID_AVP_LENGTH,
+               'Origin-Host' := _,
+               'Origin-Realm' := _,
+               'Failed-AVP' := Avps}]
+        = call(Config, Req),
+    [[_]] = failed_avps(Avps, Config).
 
 %% Send a request containing 5xxx errors that the server rejects with
 %% 3xxx.
@@ -747,14 +833,16 @@ send_invalid_reject(Config) ->
 send_unexpected_mandatory(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
 
-    ['STA', {'Session-Id', _}, {'Result-Code', ?AVP_UNSUPPORTED} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?AVP_UNSUPPORTED}]
         = call(Config, Req).
 
 %% Send something long that will be fragmented by TCP.
 send_long(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
                   {'User-Name', [binary:copy(<<$X>>, 1 bsl 20)]}],
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = call(Config, Req).
 
 %% Send something longer than the configure incoming_maxlen.
@@ -797,7 +885,8 @@ send_any_2(Config) ->
 send_all_1(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
     Realm = lists:foldr(fun(C,A) -> [C,A] end, [], ?REALM),
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = call(Config, Req, [{filter, {all, [{host, any},
                                              {realm, Realm}]}}]).
 send_all_2(Config) ->
@@ -826,13 +915,13 @@ send_detach(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
     Ref = make_ref(),
     ok = call(Config, Req, [{extra, [{self(), Ref}]}, detach]),
-    Ans = receive {Ref, T} -> T end,
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
-        = Ans.
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
+        = receive {Ref, T} -> T end.
 
 %% Send a request which can't be encoded and expect {error, encode}.
 send_encode_error(Config) ->
-    {error, encode} = call(Config, ['STR']).  %% No Termination-Cause
+    {error, encode} = call(Config, ['STR', {'Termination-Cause', huh}]).
 
 %% Send with filtering and expect success.
 send_destination_1(Config) ->
@@ -840,25 +929,27 @@ send_destination_1(Config) ->
         = group(Config),
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
                   {'Destination-Host', [?HOST(SN, ?REALM)]}],
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = call(Config, Req, [{filter, {all, [host, realm]}}]).
 send_destination_2(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT}],
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = call(Config, Req, [{filter, {all, [host, realm]}}]).
 
 %% Send with filtering on and expect failure when specifying an
 %% unknown host or realm.
 send_destination_3(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
-                  {'Destination-Realm', "unknown.org"}],
+                  {'Destination-Realm', <<"unknown.org">>}],
     {error, no_connection}
         = call(Config, Req, [{filter, {all, [host, realm]}}]).
 send_destination_4(Config) ->
     #group{server_service = SN}
         = group(Config),
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
-                  {'Destination-Host', [?HOST(SN, "unknown.org")]}],
+                  {'Destination-Host', [?HOST(SN, ["unknown.org"])]}],
     {error, no_connection}
         = call(Config, Req, [{filter, {all, [host, realm]}}]).
 
@@ -866,7 +957,7 @@ send_destination_4(Config) ->
 %% an unknown host or realm.
 send_destination_5(Config) ->
     Req = ['STR', {'Termination-Cause', ?LOGOUT},
-                  {'Destination-Realm', "unknown.org"}],
+                  {'Destination-Realm', [<<"unknown.org">>]}],
     ?answer_message(?REALM_NOT_SERVED)
         = call(Config, Req).
 send_destination_6(Config) ->
@@ -908,7 +999,8 @@ send_bad_filter(Config, F) ->
 %% Specify multiple filter options and expect them be conjunctive.
 send_multiple_filters_1(Config) ->
     Fun = fun(#diameter_caps{}) -> true end,
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = send_multiple_filters(Config, [host, {eval, Fun}]).
 send_multiple_filters_2(Config) ->
     E = {erlang, is_tuple, []},
@@ -919,7 +1011,8 @@ send_multiple_filters_3(Config) ->
     E2 = {erlang, is_tuple, []},
     E3 = {erlang, is_record, [diameter_caps]},
     E4 = [{erlang, is_record, []}, diameter_caps],
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = send_multiple_filters(Config, [{eval, E} || E <- [E1,E2,E3,E4]]).
 
 send_multiple_filters(Config, Fs) ->
@@ -930,11 +1023,35 @@ send_multiple_filters(Config, Fs) ->
 %% only the return value from the prepare_request callback being
 %% significant.
 send_anything(Config) ->
-    ['STA', {'Session-Id', _}, {'Result-Code', ?SUCCESS} | _]
+    ['STA' | #{'Session-Id' := _,
+               'Result-Code' := ?SUCCESS}]
         = call(Config, anything).
 
 %% ===========================================================================
 
+failed_avps(Avps, Config) ->
+    #group{client_dict = D} = proplists:get_value(group, Config),
+    [failed_avp(D, T) || T <- Avps].
+
+failed_avp(nas4005, {'nas_Failed-AVP', As}) ->
+    As;
+failed_avp(_, #'diameter_base_Failed-AVP'{'AVP' = As}) ->
+    As.
+
+proxy_info(Rec, Config) ->
+    #group{client_dict = D} = proplists:get_value(group, Config),
+    if D == nas4005 ->
+            {'nas_Proxy-Info', H, S, As}
+                = Rec,
+            {H,S,As};
+       true ->
+            #'diameter_base_Proxy-Info'{'Proxy-Host' = H,
+                                        'Proxy-State' = S,
+                                        'AVP' = As}
+                = Rec,
+            {H,S,As}
+    end.
+
 group(Config) ->
     #group{} = proplists:get_value(group, Config).
 
@@ -954,58 +1071,135 @@ call(Config, Req) ->
 
 call(Config, Req, Opts) ->
     Name = proplists:get_value(testcase, Config),
-    #group{client_service = CN,
-           client_encoding = ReqEncoding,
-           client_dict0 = Dict0}
-        = Group
+    #group{encoding = Enc,
+           client_service = CN,
+           client_dict = Dict0}
         = group(Config),
     diameter:call(CN,
                   dict(Req, Dict0),
-                  msg(Req, ReqEncoding, Dict0),
-                  [{extra, [{Name, Group}, diameter_lib:now()]} | Opts]).
+                  msg(Req, Enc, Dict0),
+                  [{extra, [Name, diameter_lib:now()]} | Opts]).
 
-origin({A,C}) ->
-    2*codec(A) + container(C);
+origin({D,E}) ->
+    4*decode(D) + encode(E);
 
 origin(N) ->
-    {codec(N band 2), container(N rem 2)}.
-
-%% Map booleans, but the readable atoms are part of (constructed)
-%% group names, so it's good that they're readable.
-
-codec(record) -> 0;
-codec(list)   -> 1;
-codec(0) -> record;
-codec(_) -> list.
-
-container(pkt) -> 0;
-container(msg) -> 1;
-container(0) -> pkt;
-container(_) -> msg.
+    {decode(N bsr 2), encode(N rem 4)}.
+
+%% Map atoms. The atoms are part of (constructed) group names, so it's
+%% good that they're readable.
+
+decode(record) -> 0;
+decode(list)   -> 1;
+decode(map)    -> 2;
+decode(false)  -> 3;
+decode(record_from_map) -> 4;
+decode(0) -> record;
+decode(1) -> list;
+decode(2) -> map;
+decode(3) -> false;
+decode(4) -> record_from_map.
+
+encode(record) -> 0;
+encode(list)   -> 1;
+encode(map)    -> 2;
+encode(0) -> record;
+encode(1) -> list;
+encode(2) -> map.
 
 msg([H|_] = Msg, record = E, diameter_gen_base_rfc3588)
   when H == 'ACR';
        H == 'ACA' ->
     msg(Msg, E, diameter_gen_base_accounting);
+
 msg([H|_] = Msg, record = E, diameter_gen_base_rfc6733)
   when H == 'ACR';
        H == 'ACA' ->
     msg(Msg, E, diameter_gen_acct_rfc6733);
+
 msg([H|T], record, Dict) ->
     Dict:'#new-'(Dict:msg2rec(H), T);
+
+msg([H|As], map, _)
+  when is_list(As) ->
+    [H | maps:from_list(As)];
+
 msg(Msg, _, _) ->
     Msg.
 
+to_map(#diameter_packet{msg = [_MsgName | Avps] = Msg},
+       #group{server_decoding = map})
+  when is_map(Avps) ->
+    Msg;
+
+to_map(#diameter_packet{msg = [MsgName | Avps]},
+       #group{server_decoding = list}) ->
+    [MsgName | maps:from_list(Avps)];
+
+to_map(#diameter_packet{header = H, msg = Rec},
+       #group{server_decoding = D})
+  when D == record;
+       D == record_from_map ->
+    rec_to_map(Rec, dict(H));
+
+%% No record decode: do it ourselves.
+to_map(#diameter_packet{header = H,
+                        msg = false,
+                        bin = Bin},
+      #group{server_decoding = false,
+             strings = B}) ->
+    Opts = #{decode_format => map,
+             string_decode => B,
+             strict_mbit => true,
+             rfc => 6733},
+    #diameter_packet{msg = [_MsgName | _Map] = Msg}
+        = diameter_codec:decode(dict(H), Opts, Bin),
+    Msg.
+
+dict(#diameter_header{application_id = Id,
+                      cmd_code = Code}) ->
+    if Id == 1 ->
+            nas4005;
+       Code == 271 ->
+            diameter_gen_base_accounting;
+       true ->
+            diameter_gen_base_rfc3588
+    end.
+
+rec_to_map(Rec, Dict) ->
+    [R | Vs] = Dict:'#get-'(Rec),
+    [Dict:rec2msg(R) | maps:from_list([T || {_,V} = T <- Vs,
+                                            V /= undefined,
+                                            V /= []])].
+
+appdict(rfc4005) ->
+    nas4005;
+appdict(D) ->
+    dict0(D).
+
 dict0(D) ->
     ?A("diameter_gen_base_" ++ ?L(D)).
 
-dict(Msg, Dict0)
-  when 'ACR' == hd(Msg);
-       'ACA' == hd(Msg);
-       ?is_record(Msg, diameter_base_accounting_ACR);
-       ?is_record(Msg, diameter_base_accounting_ACA) ->
+dict(Msg, Dict) ->
+    d(name(Msg), Dict).
+
+d(N, nas4005 = D) ->
+    if N == {list, 'answer-message'};
+       N == {map, 'answer-message'};
+       N == {record, 'diameter_base_answer-message'} ->
+            diameter_gen_base_rfc3588;
+       true ->
+            D
+    end;
+d(N, Dict0)
+  when N == {list, 'ACR'};
+       N == {list, 'ACA'};
+       N == {map, 'ACR'};
+       N == {map, 'ACA'};
+       N == {record, diameter_base_accounting_ACR};
+       N == {record, diameter_base_accounting_ACA} ->
     acct(Dict0);
-dict(_, Dict0) ->
+d(_, Dict0) ->
     Dict0.
 
 acct(diameter_gen_base_rfc3588) ->
@@ -1014,53 +1208,60 @@ acct(diameter_gen_base_rfc6733) ->
     diameter_gen_acct_rfc6733.
 
 %% Set only values that aren't already.
-set(_, [H|T], Vs) ->
-    [H | Vs ++ T];
-set(#group{client_dict0 = Dict0} = _Group, Rec, Vs) ->
+
+set(_, [N | As], Vs) ->
+    [N | if is_map(As) ->
+                 maps:merge(maps:from_list(Vs), As);
+            is_list(As) ->
+                 Vs ++ As
+         end];
+
+set(#group{client_dict = Dict0} = _Group, Rec, Vs) ->
     Dict = dict(Rec, Dict0),
     lists:foldl(fun({F,_} = FV, A) ->
-                        set(Dict, Dict:'#get-'(F, A), FV, A)
+                        reset(Dict, Dict:'#get-'(F, A), FV, A)
                 end,
                 Rec,
                 Vs).
 
-set(Dict, E, FV, Rec)
+reset(Dict, E, FV, Rec)
   when E == undefined;
        E == [] ->
     Dict:'#set-'(FV, Rec);
-set(_, _, _, Rec) ->
+
+reset(_, _, _, Rec) ->
     Rec.
 
 %% ===========================================================================
 %% diameter callbacks
 
-%% peer_up/3
+%% peer_up/4
 
-peer_up(_SvcName, _Peer, State) ->
+peer_up(_SvcName, _Peer, State, _Group) ->
     State.
 
 %% peer_down/3
 
-peer_down(_SvcName, _Peer, State) ->
+peer_down(_SvcName, _Peer, State, _Group) ->
     State.
 
-%% pick_peer/6-7
+%% pick_peer/7-8
 
-pick_peer(Peers, _, [$C|_], _State, {Name, Group}, _)
+pick_peer(Peers, _, [$C|_], _State, Group, Name, _)
   when Name /= send_detach ->
     find(Group, Peers).
 
-pick_peer(_Peers, _, [$C|_], _State, {send_nopeer, _}, _, ?EXTRA) ->
+pick_peer(_Peers, _, [$C|_], _State, _Group, send_nopeer, _, ?EXTRA) ->
     false;
 
-pick_peer(Peers, _, [$C|_], _State, {send_detach, Group}, _, {_,_}) ->
+pick_peer(Peers, _, [$C|_], _State, Group, send_detach, _, {_,_}) ->
     find(Group, Peers).
 
-find(#group{client_service = CN,
-            server_encoding = A,
-            server_container = C},
+find(#group{encoding = E,
+            client_service = CN,
+            server_decoding = D},
      [_|_] = Peers) ->
-    Id = {A,C},
+    Id = {D,E},
     [P] = [P || P <- Peers, id(Id, P, CN)],
     {ok, P}.
 
@@ -1069,15 +1270,15 @@ id(Id, {Pid, _Caps}, SvcName) ->
         = diameter:service_info(SvcName, Pid),
     lists:member({id, Id}, Opts).
 
-%% prepare_request/5-6
+%% prepare_request/6-7
 
-prepare_request(_Pkt, [$C|_], {_Ref, _Caps}, {send_discard, _}, _) ->
+prepare_request(_Pkt, [$C|_], {_Ref, _Caps}, _, send_discard, _) ->
     {discard, unprepared};
 
-prepare_request(Pkt, [$C|_], {_Ref, Caps}, {Name, Group}, _) ->
+prepare_request(Pkt, [$C|_], {_Ref, Caps}, Group, Name, _) ->
     {send, prepare(Pkt, Caps, Name, Group)}.
 
-prepare_request(Pkt, [$C|_], {_Ref, Caps}, {send_detach, Group}, _, _) ->
+prepare_request(Pkt, [$C|_], {_Ref, Caps}, Group, send_detach, _, _) ->
     {eval_packet, {send, prepare(Pkt, Caps, Group)}, [fun log/2, detach]}.
 
 log(#diameter_packet{bin = Bin} = P, T)
@@ -1086,7 +1287,7 @@ log(#diameter_packet{bin = Bin} = P, T)
 
 %% prepare/4
 
-prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
+prepare(Pkt, Caps, N, #group{client_dict = Dict0} = Group)
   when N == send_unknown_short_mandatory;
        N == send_unknown_short ->
     Req = prepare(Pkt, Caps, Group),
@@ -1106,7 +1307,7 @@ prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
     <<H:Offset/binary, Len:24, T/binary>> = Bin,
     E#diameter_packet{bin = <<H/binary, (Len+9):24, T/binary>>};
 
-prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
+prepare(Pkt, Caps, N, #group{client_dict = Dict0} = Group)
   when N == send_long_avp_length;
        N == send_short_avp_length;
        N == send_zero_avp_length ->
@@ -1132,7 +1333,7 @@ prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
                               T/binary,
                               Hdr/binary, AL:24, Data/binary>>};
 
-prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
+prepare(Pkt, Caps, N, #group{client_dict = Dict0} = Group)
   when N == send_invalid_avp_length;
        N == send_invalid_reject ->
     Req = prepare(Pkt, Caps, Group),
@@ -1147,7 +1348,7 @@ prepare(Pkt, Caps, N, #group{client_dict0 = Dict0} = Group)
     <<V, L:24, H/binary>> = H0,  %% assert
     E#diameter_packet{bin = <<V, (L+4):24, H/binary, 16:24, 0:32, T/binary>>};
 
-prepare(Pkt, Caps, send_unexpected_mandatory, #group{client_dict0 = Dict0}
+prepare(Pkt, Caps, send_unexpected_mandatory, #group{client_dict = Dict0}
                                               = Group) ->
     Req = prepare(Pkt, Caps, Group),
     #diameter_packet{bin = <<V, Len:24, T/binary>>}
@@ -1157,7 +1358,7 @@ prepare(Pkt, Caps, send_unexpected_mandatory, #group{client_dict0 = Dict0}
     Avp = <<Code:32, Flags, 8:24>>,
     E#diameter_packet{bin = <<V, (Len+8):24, T/binary, Avp/binary>>};
 
-prepare(Pkt, Caps, send_grouped_error, #group{client_dict0 = Dict0}
+prepare(Pkt, Caps, send_grouped_error, #group{client_dict = Dict0}
                                               = Group) ->
     Req = prepare(Pkt, Caps, Group),
     #diameter_packet{bin = Bin}
@@ -1189,14 +1390,14 @@ prepare(Pkt, Caps, send_grouped_error, #group{client_dict0 = Dict0}
                               Payload/binary,
                               T/binary>>};
 
-prepare(Pkt, Caps, send_unsupported, #group{client_dict0 = Dict0} = Group) ->
+prepare(Pkt, Caps, send_unsupported, #group{client_dict = Dict0} = Group) ->
     Req = prepare(Pkt, Caps, Group),
     #diameter_packet{bin = <<H:5/binary, _CmdCode:3/binary, T/binary>>}
         = E
         = diameter_codec:encode(Dict0, Pkt#diameter_packet{msg = Req}),
     E#diameter_packet{bin = <<H/binary, 42:24, T/binary>>};
 
-prepare(Pkt, Caps, send_unsupported_app, #group{client_dict0 = Dict0}
+prepare(Pkt, Caps, send_unsupported_app, #group{client_dict = Dict0}
                                          = Group) ->
     Req = prepare(Pkt, Caps, Group),
     #diameter_packet{bin = <<H:8/binary, _ApplId:4/binary, T/binary>>}
@@ -1223,77 +1424,105 @@ prepare(Pkt, Caps, _Name, Group) ->
 
 %% prepare/3
 
-prepare(#diameter_packet{msg = Req}, Caps, Group)
-  when ?is_record(Req, diameter_base_accounting_ACR);
-       'ACR' == hd(Req) ->
+prepare(#diameter_packet{msg = Req} = Pkt, Caps, Group) ->
+    set(name(Req), Pkt, Caps, Group).
+
+%% set/4
+
+set(N, #diameter_packet{msg = Req}, Caps, Group)
+  when N == {record, diameter_base_accounting_ACR};
+       N == {record, nas_ACR};
+       N == {map, 'ACR'};
+       N == {list, 'ACR'} ->
     #diameter_caps{origin_host  = {OH, _},
                    origin_realm = {OR, DR}}
         = Caps,
 
-    set(Group, Req, [{'Session-Id', diameter:session_id(OH)},
-                     {'Origin-Host',  OH},
-                     {'Origin-Realm', OR},
-                     {'Destination-Realm', DR}]);
+    set(Group, Req, [{'Session-Id', [diameter:session_id(OH)]},
+                     {'Origin-Host',  [OH]},
+                     {'Origin-Realm', [OR]},
+                     {'Destination-Realm', [DR]}]);
 
-prepare(#diameter_packet{msg = Req}, Caps, Group)
-  when ?is_record(Req, diameter_base_ASR);
-       'ASR' == hd(Req) ->
+set(N, #diameter_packet{msg = Req}, Caps, Group)
+  when N == {record, diameter_base_ASR};
+       N == {record, nas_ASR};
+       N == {map, 'ASR'};
+       N == {list, 'ASR'} ->
     #diameter_caps{origin_host  = {OH, DH},
                    origin_realm = {OR, DR}}
         = Caps,
-    set(Group, Req, [{'Session-Id', diameter:session_id(OH)},
-                     {'Origin-Host',  OH},
-                     {'Origin-Realm', OR},
-                     {'Destination-Host',  DH},
-                     {'Destination-Realm', DR},
+    set(Group, Req, [{'Session-Id', [diameter:session_id(OH)]},
+                     {'Origin-Host',  [OH]},
+                     {'Origin-Realm', [OR]},
+                     {'Destination-Host',  [DH]},
+                     {'Destination-Realm', [DR]},
                      {'Auth-Application-Id', ?APP_ID}]);
 
-prepare(#diameter_packet{msg = Req}, Caps, Group)
-  when ?is_record(Req, diameter_base_STR);
-       'STR' == hd(Req) ->
+set(N, #diameter_packet{msg = Req}, Caps, Group)
+  when N == {record, diameter_base_STR};
+       N == {record, nas_STR};
+       N == {map, 'STR'};
+       N == {list, 'STR'} ->
     #diameter_caps{origin_host  = {OH, _},
                    origin_realm = {OR, DR}}
         = Caps,
-    set(Group, Req, [{'Session-Id', diameter:session_id(OH)},
-                     {'Origin-Host',  OH},
-                     {'Origin-Realm', OR},
-                     {'Destination-Realm', DR},
+    set(Group, Req, [{'Session-Id', [diameter:session_id(OH)]},
+                     {'Origin-Host',  [OH]},
+                     {'Origin-Realm', [OR]},
+                     {'Destination-Realm', [DR]},
                      {'Auth-Application-Id', ?APP_ID}]);
 
-prepare(#diameter_packet{msg = Req}, Caps, Group)
-  when ?is_record(Req, diameter_base_RAR);
-       'RAR' == hd(Req) ->
+set(N, #diameter_packet{msg = Req}, Caps, Group)
+  when N == {record, diameter_base_RAR};
+       N == {record, nas_RAR};
+       N == {map, 'RAR'};
+       N == {list, 'RAR'} ->
     #diameter_caps{origin_host  = {OH, DH},
                    origin_realm = {OR, DR}}
         = Caps,
-    set(Group, Req, [{'Session-Id', diameter:session_id(OH)},
-                     {'Origin-Host',  OH},
-                     {'Origin-Realm', OR},
-                     {'Destination-Host',  DH},
-                     {'Destination-Realm', DR},
+    set(Group, Req, [{'Session-Id', [diameter:session_id(OH)]},
+                     {'Origin-Host',  [OH]},
+                     {'Origin-Realm', [OR]},
+                     {'Destination-Host',  [DH]},
+                     {'Destination-Realm', [DR]},
                      {'Auth-Application-Id', ?APP_ID}]).
 
-%% prepare_retransmit/5
+%% name/1
+
+name([H|#{}]) ->
+    {map, H};
 
-prepare_retransmit(_Pkt, false, _Peer, _Name, _Group) ->
+name([H|_]) ->
+    {list, H};
+
+name(Rec) ->
+    try
+        {record, element(1, Rec)}
+    catch
+        error: badarg ->
+            false
+    end.
+
+%% prepare_retransmit/6
+
+prepare_retransmit(_Pkt, false, _Peer, _Group, _Name, _) ->
     discard.
 
-%% handle_answer/6-7
+%% handle_answer/7-8
 
-handle_answer(Pkt, Req, [$C|_], Peer, {Name, Group}, _) ->
+handle_answer(Pkt, Req, [$C|_], Peer, Group, Name, _) ->
     answer(Pkt, Req, Peer, Name, Group).
 
-handle_answer(Pkt, Req, [$C|_], Peer, {send_detach = Name, Group}, _, X) ->
+handle_answer(Pkt, Req, [$C|_], Peer, Group, send_detach = Name, _, X) ->
     {Pid, Ref} = X,
     Pid ! {Ref, answer(Pkt, Req, Peer, Name, Group)}.
 
-answer(Pkt, Req, _Peer, Name, #group{client_dict0 = Dict0}) ->
+answer(Pkt, Req, _Peer, Name, #group{client_dict = Dict0}) ->
     #diameter_packet{header = H, msg = Ans, errors = Es} = Pkt,
     ApplId = app(Req, Name, Dict0),
     #diameter_header{application_id = ApplId} = H,  %% assert
     Dict = dict(Ans, Dict0),
-    [R | Vs] = Dict:'#get-'(answer(Ans, Es, Name)),
-    [Dict:rec2msg(R) | Vs].
+    rec_to_map(answer(Ans, Es, Name), Dict).
 
 %% Missing Result-Code and inappropriate Experimental-Result-Code.
 answer(Rec, Es, send_experimental_result) ->
@@ -1317,25 +1546,29 @@ app(Req, _, Dict0) ->
     Dict = dict(Req, Dict0),
     Dict:id().
 
-%% handle_error/6
+%% handle_error/7
 
-handle_error(timeout = Reason, _Req, [$C|_], _Peer, _, Time) ->
+handle_error(timeout = Reason, _Req, [$C|_], _Peer, _, _, Time) ->
     Now = diameter_lib:now(),
     {Reason, {diameter_lib:timestamp(Time),
               diameter_lib:timestamp(Now),
               diameter_lib:micro_diff(Now, Time)}};
 
-handle_error(Reason, _Req, [$C|_], _Peer, _, _Time) ->
+handle_error(Reason, _Req, [$C|_], _Peer, _, _, _Time) ->
     {error, Reason}.
 
-%% handle_request/3
+%% handle_request/4
 
 %% Note that diameter will set Result-Code and Failed-AVPs if
 %% #diameter_packet.errors is non-null.
 
-handle_request(#diameter_packet{header = H, msg = M, avps = As},
+handle_request(#diameter_packet{header = H, avps = As}
+               = Pkt,
                _,
-               {_Ref, Caps}) ->
+               {_Ref, Caps},
+               #group{encoding = E,
+                      server_decoding = D}
+               = Grp) ->
     #diameter_header{end_to_end_id = EI,
                      hop_by_hop_id = HI}
         = H,
@@ -1343,24 +1576,62 @@ handle_request(#diameter_packet{header = H, msg = M, avps = As},
     V = EI bsr B,  %% assert
     V = HI bsr B,  %%
     #diameter_caps{origin_state_id = {_,[Id]}} = Caps,
-    answer(origin(Id), request(M, [H|As], Caps)).
+    {D,E} = T = origin(Id),  %% assert
+    wrap(T, H, request(to_map(Pkt, Grp), [H|As], Caps)).
+
+wrap(Id, H, {Tag, Action, Post}) ->
+    {Tag, wrap(Id, H, Action), Post};
 
-answer(T, {Tag, Action, Post}) ->
-    {Tag, answer(T, Action), Post};
-answer(_, {reply, [#diameter_header{} | _]} = T) ->
+wrap(_, _, {reply, [#diameter_header{} | _]} = T) ->
     T;
-answer({A,C}, {reply, Ans}) ->
-    answer(C, {reply, msg(Ans, A, diameter_gen_base_rfc3588)});
-answer(pkt, {reply, Ans})
-  when not is_record(Ans, diameter_packet) ->
-    {reply, #diameter_packet{msg = Ans}};
-answer(_, T) ->
+
+wrap({_,E}, H, {reply, Ans}) ->
+    Msg = base_to_nas(msg(Ans, E, diameter_gen_base_rfc3588), H),
+    {reply, wrap(Msg)};
+
+wrap(_, _, T) ->
     T.
 
+%% Randomly wrap the answer in a diameter_packet.
+
+wrap(#diameter_packet{} = Pkt) ->
+    Pkt;
+
+wrap(Msg) ->
+    case rand:uniform(2) of
+        1 -> #diameter_packet{msg = Msg};
+        2 -> Msg
+    end.
+
+%% base_to_nas/2
+
+base_to_nas(#diameter_packet{msg = Msg} = Pkt, H) ->
+    Pkt#diameter_packet{msg = base_to_nas(Msg, H)};
+
+base_to_nas(Rec, #diameter_header{application_id = 1})
+  when is_tuple(Rec), not ?is_record(Rec, 'diameter_base_answer-message') ->
+    D = case element(1, Rec) of
+            diameter_base_accounting_ACA ->
+                diameter_gen_base_accounting;
+            _ ->
+                diameter_gen_base_rfc3588
+        end,
+    [R | Values] = D:'#get-'(Rec),
+    "diameter_base_" ++ N = ?L(R),
+    Name = ?A("nas_" ++ if N == "accounting_ACA" ->
+                                "ACA";
+                           true ->
+                                N
+                        end),
+    nas4005:'#new-'([Name | Values]);
+
+base_to_nas(Msg, _) ->
+    Msg.
+
 %% request/3
 
 %% send_experimental_result
-request(#diameter_base_accounting_ACR{'Accounting-Record-Number' = 5},
+request(['ACR' | #{'Accounting-Record-Number' := 5}],
         [Hdr | Avps],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
@@ -1393,14 +1664,14 @@ request(Msg, _Avps, Caps) ->
 %% request/2
 
 %% send_nok
-request(#diameter_base_accounting_ACR{'Accounting-Record-Number' = 0},
+request(['ACR' | #{'Accounting-Record-Number' := 0}],
         _) ->
     {eval_packet, {protocol_error, ?INVALID_AVP_BITS}, [fun log/2, invalid]};
 
 %% send_bad_answer
-request(#diameter_base_accounting_ACR{'Session-Id' = SId,
-                                      'Accounting-Record-Type' = RT,
-                                      'Accounting-Record-Number' = 2 = RN},
+request(['ACR' | #{'Session-Id' := SId,
+                   'Accounting-Record-Type' := RT,
+                   'Accounting-Record-Number' := 2 = RN}],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
     Ans = ['ACA', {'Result-Code', ?SUCCESS},
@@ -1414,9 +1685,9 @@ request(#diameter_base_accounting_ACR{'Session-Id' = SId,
                              msg = Ans}};
 
 %% send_eval
-request(#diameter_base_accounting_ACR{'Session-Id' = SId,
-                                      'Accounting-Record-Type' = RT,
-                                      'Accounting-Record-Number' = 3 = RN},
+request(['ACR' | #{'Session-Id' := SId,
+                   'Accounting-Record-Type' := RT,
+                   'Accounting-Record-Number' := 3 = RN}],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
     Ans = ['ACA', {'Result-Code', ?SUCCESS},
@@ -1428,9 +1699,9 @@ request(#diameter_base_accounting_ACR{'Session-Id' = SId,
     {eval, {reply, Ans}, {erlang, now, []}};
 
 %% send_ok
-request(#diameter_base_accounting_ACR{'Session-Id' = SId,
-                                      'Accounting-Record-Type' = RT,
-                                      'Accounting-Record-Number' = 1 = RN},
+request(['ACR' | #{'Session-Id' := SId,
+                   'Accounting-Record-Type' := RT,
+                   'Accounting-Record-Number' := 1 = RN}],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
     {reply, ['ACA', {'Result-Code', ?SUCCESS},
@@ -1441,7 +1712,7 @@ request(#diameter_base_accounting_ACR{'Session-Id' = SId,
                     {'Accounting-Record-Number', RN}]};
 
 %% send_protocol_error
-request(#diameter_base_accounting_ACR{'Accounting-Record-Number' = 4},
+request(['ACR' | #{'Accounting-Record-Number' := 4}],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
     Ans = ['answer-message', {'Result-Code', ?TOO_BUSY},
@@ -1449,40 +1720,39 @@ request(#diameter_base_accounting_ACR{'Accounting-Record-Number' = 4},
                              {'Origin-Realm', OR}],
     {reply, Ans};
 
-request(#diameter_base_ASR{'Session-Id' = SId,
-                           'AVP' = Avps},
+request(['ASR' | #{'Session-Id' := SId} = Avps],
         #diameter_caps{origin_host = {OH, _},
                        origin_realm = {OR, _}}) ->
     {reply, ['ASA', {'Result-Code', ?SUCCESS},
                     {'Session-Id', SId},
                     {'Origin-Host', OH},
                     {'Origin-Realm', OR},
-                    {'AVP', Avps}]};
+                    {'AVP', maps:get('AVP', Avps, [])}]};
 
 %% send_invalid_reject
-request(#diameter_base_STR{'Termination-Cause' = ?USER_MOVED},
+request(['STR' | #{'Termination-Cause' := ?USER_MOVED}],
         _Caps) ->
     {protocol_error, ?TOO_BUSY};
 
 %% send_noreply
-request(#diameter_base_STR{'Termination-Cause' = T},
+request(['STR' | #{'Termination-Cause' := T}],
         _Caps)
   when T /= ?LOGOUT ->
     discard;
 
 %% send_destination_5
-request(#diameter_base_STR{'Destination-Realm' = R},
+request(['STR' | #{'Destination-Realm' := R}],
         #diameter_caps{origin_realm = {OR, _}})
   when R /= undefined, R /= OR ->
     {protocol_error, ?REALM_NOT_SERVED};
 
 %% send_destination_6
-request(#diameter_base_STR{'Destination-Host' = [H]},
+request(['STR' | #{'Destination-Host' := [H]}],
         #diameter_caps{origin_host = {OH, _}})
   when H /= OH ->
     {protocol_error, ?UNABLE_TO_DELIVER};
 
-request(#diameter_base_STR{'Session-Id' = SId},
+request(['STR' | #{'Session-Id' := SId}],
         #diameter_caps{origin_host  = {OH, _},
                        origin_realm = {OR, _}}) ->
     {reply, ['STA', {'Result-Code', ?SUCCESS},
@@ -1491,7 +1761,7 @@ request(#diameter_base_STR{'Session-Id' = SId},
                     {'Origin-Realm', OR}]};
 
 %% send_error/send_timeout
-request(#diameter_base_RAR{}, _Caps) ->
+request(['RAR' | #{}], _Caps) ->
     receive after 2000 -> {protocol_error, ?TOO_BUSY} end.
 
 %% message/3
@@ -1505,8 +1775,8 @@ message(Dir, #diameter_packet{bin = Bin}, N) ->
     message(Dir, Bin, N);
 
 %% incoming request
-message(recv, <<_:32, 1, _/bits>> = Bin, N) ->
-    [Bin, 1 < N, fun ?MODULE:message/3, N-1];
+message(recv, <<_:32, 1:1, _/bits>> = Bin, N) ->
+    [Bin, N < 16, fun ?MODULE:message/3, N+1];
 
 %% incoming answer
 message(recv, Bin, _) ->
@@ -1517,9 +1787,35 @@ message(send, Bin, _) ->
     [Bin];
 
 %% sent request
-message(ack, <<_:32, 1, _/bits>>, _) ->
+message(ack, <<_:32, 1:1, _/bits>>, _) ->
     [];
 
 %% sent answer or discarded request
 message(ack, _, N) ->
-    [0 =< N, fun ?MODULE:message/3, N+1].
+    [N =< 16, fun ?MODULE:message/3, N-1].
+
+%% ------------------------------------------------------------------------
+
+compile_and_load() ->
+    try
+        Path = hd([P || H <- [[here(), ".."], [code:lib_dir(diameter)]],
+                        P <- [filename:join(H ++ ["examples",
+                                                  "dict",
+                                                  "rfc4005_nas.dia"])],
+                        {ok, _} <- [file:read_file_info(P)]]),
+        {ok, [Forms]}
+            = diameter_make:codec(Path, [return,
+                                      forms,
+                                   {name, "nas4005"},
+                                {prefix, "nas"},
+                             {inherits, "common/diameter_gen_base_rfc3588"}]),
+        {ok, nas4005, Bin, []} = compile:forms(Forms, [debug_info, return]),
+        {module, nas4005} = code:load_binary(nas4005, "nas4005", Bin),
+        true
+    catch
+        E:R ->
+            {E, R, erlang:get_stacktrace()}
+    end.
+
+here() ->
+    filename:dirname(code:which(?MODULE)).
diff --git a/lib/diameter/test/diameter_util.erl b/lib/diameter/test/diameter_util.erl
index 03f79096ac..d249b0e4fa 100644
--- a/lib/diameter/test/diameter_util.erl
+++ b/lib/diameter/test/diameter_util.erl
@@ -32,7 +32,8 @@
          foldl/3,
          scramble/1,
          unique_string/0,
-         have_sctp/0]).
+         have_sctp/0,
+         eprof/1]).
 
 %% diameter-specific
 -export([lport/2,
@@ -48,6 +49,16 @@
 
 -define(L, atom_to_list).
 
+%% ---------------------------------------------------------------------------
+
+eprof(start) ->
+    eprof:start(),
+    eprof:start_profiling([self()]);
+
+eprof(stop) ->
+    eprof:stop_profiling(),
+    eprof:analyze(),
+    eprof:stop().
 
 %% ---------------------------------------------------------------------------
 %% name/2