diff --git a/apps/sdlan/src/network/arp_packet.erl b/apps/sdlan/src/network/arp_packet.erl
new file mode 100644
index 0000000..0a22300
--- /dev/null
+++ b/apps/sdlan/src/network/arp_packet.erl
@@ -0,0 +1,153 @@
+%%%-------------------------------------------------------------------
+%%% @doc ARP packet parser / builder (Ethernet + IPv4)
+%%%-------------------------------------------------------------------
+-module(arp_packet).
+
+-export([parse/1, marshal/1, is_broadcast_mac/1, arp_request/3, arp_response/3]).
+
+-define(ARP_REQUEST,  1).
+-define(ARP_RESPONSE, 2).
+
+-define(ETHERNET, 16#0001).
+-define(IPV4,     16#0800).
+
+-define(BROADCAST_MAC, <<255,255,255,255,255,255>>).
+
+-record(arp_packet, {
+    hardware_type,
+    protocol_type,
+    hardware_size,
+    protocol_size,
+    opcode,
+    sender_mac,
+    sender_ip,
+    target_mac,
+    target_ip
+}).
+
+%%--------------------------------------------------------------------
+%% Parsing
+%%--------------------------------------------------------------------
+
+-spec parse(binary()) ->
+    {ok, #arp_packet{}} | {error, invalid_length | invalid_opcode}.
+parse(Bin) when is_binary(Bin) ->
+    case Bin of
+        <<
+            HType:16/big,
+            PType:16/big,
+            HLen:8,
+            PLen:8,
+            Op:16/big,
+            SMac:6/binary,
+            SIP:32/big,
+            TMac:6/binary,
+            TIP:32/big,
+            _/binary
+        >> ->
+            case decode_opcode(Op) of
+                {ok, Opcode} ->
+                    {ok, #arp_packet{
+                        hardware_type = HType,
+                        protocol_type = PType,
+                        hardware_size = HLen,
+                        protocol_size = PLen,
+                        opcode        = Opcode,
+                        sender_mac    = SMac,
+                        sender_ip     = SIP,
+                        target_mac    = TMac,
+                        target_ip     = TIP
+                    }};
+                error ->
+                    {error, invalid_opcode}
+            end;
+        _ ->
+            {error, invalid_length}
+    end.
+
+%%--------------------------------------------------------------------
+%% Marshal
+%%--------------------------------------------------------------------
+
+-spec marshal(#arp_packet{}) -> binary().
+marshal(#arp_packet{
+    hardware_type = HType,
+    protocol_type = PType,
+    hardware_size = HLen,
+    protocol_size = PLen,
+    opcode        = Opcode,
+    sender_mac    = SMac,
+    sender_ip     = SIP,
+    target_mac    = TMac,
+    target_ip     = TIP
+}) ->
+    Op = encode_opcode(Opcode),
+    <<
+        HType:16/big,
+        PType:16/big,
+        HLen:8,
+        PLen:8,
+        Op:16/big,
+        SMac/binary,
+        SIP:32/big,
+        TMac/binary,
+        TIP:32/big
+    >>.
+
+%%--------------------------------------------------------------------
+%% Opcode helpers
+%%--------------------------------------------------------------------
+
+decode_opcode(?ARP_REQUEST)  -> {ok, request};
+decode_opcode(?ARP_RESPONSE) -> {ok, response};
+decode_opcode(_)             -> error.
+
+encode_opcode(request)  -> ?ARP_REQUEST;
+encode_opcode(response) -> ?ARP_RESPONSE.
+
+%%--------------------------------------------------------------------
+%% Utils
+%%--------------------------------------------------------------------
+
+-spec is_broadcast_mac(binary()) -> boolean().
+is_broadcast_mac(?BROADCAST_MAC) -> true;
+is_broadcast_mac(_)              -> false.
+
+%%--------------------------------------------------------------------
+%% Builders (对齐 Swift 扩展)
+%%--------------------------------------------------------------------
+
+-spec arp_request(integer(), binary(), integer()) -> #arp_packet{}.
+arp_request(SenderIP, SenderMAC, TargetIP) ->
+    #arp_packet{
+        hardware_type = ?ETHERNET,
+        protocol_type = ?IPV4,
+        hardware_size = 6,
+        protocol_size = 4,
+        opcode        = request,
+        sender_mac    = SenderMAC,
+        sender_ip     = SenderIP,
+        target_mac    = <<0,0,0,0,0,0>>,
+        target_ip     = TargetIP
+    }.
+
+-spec arp_response(#arp_packet{}, binary(), integer()) -> #arp_packet{}.
+arp_response(#arp_packet{
+    hardware_type = HType,
+    protocol_type = PType,
+    hardware_size = HLen,
+    protocol_size = PLen,
+    sender_mac    = ReqMac,
+    sender_ip     = ReqIP
+}, Mac, IP) ->
+    #arp_packet{
+        hardware_type = HType,
+        protocol_type = PType,
+        hardware_size = HLen,
+        protocol_size = PLen,
+        opcode        = response,
+        sender_mac    = Mac,
+        sender_ip     = IP,
+        target_mac    = ReqMac,
+        target_ip     = ReqIP
+    }.
\ No newline at end of file
diff --git a/apps/sdlan/src/network/layer_packet.erl b/apps/sdlan/src/network/layer_packet.erl
new file mode 100644
index 0000000..c3e73bc
--- /dev/null
+++ b/apps/sdlan/src/network/layer_packet.erl
@@ -0,0 +1,88 @@
+%%%-------------------------------------------------------------------
+%%% @doc Ethernet II layer packet parser
+%%%-------------------------------------------------------------------
+-module(layer_packet).
+
+-export([parse/1, marshal/1, is_broadcast_mac/1, is_multicast_mac/1]).
+
+-define(ETH_ARP, 16#0806).
+-define(ETH_IPV4, 16#0800).
+-define(ETH_IPV6, 16#86DD).
+-define(ETH_VLAN, 16#8100).
+
+-record(layer_packet, {
+    dst_mac,
+    src_mac,
+    type,
+    payload
+}).
+
+%%--------------------------------------------------------------------
+%% API
+%%--------------------------------------------------------------------
+
+-spec parse(binary()) -> {ok, #layer_packet{}} | {error, invalid_length | invalid_type}.
+parse(Bin) when is_binary(Bin) ->
+    case Bin of
+        <<Dst:6/binary, Src:6/binary, Type:16, Payload/binary>> ->
+            case decode_type(Type) of
+                {ok, T} ->
+                    {ok, #layer_packet{
+                        dst_mac = Dst,
+                        src_mac = Src,
+                        type    = T,
+                        payload = Payload
+                    }};
+                error ->
+                    {error, invalid_type}
+            end;
+        _ ->
+            {error, invalid_length}
+    end.
+
+%%--------------------------------------------------------------------
+
+-spec marshal(#layer_packet{}) -> binary().
+marshal(#layer_packet{dst_mac = Dst, src_mac = Src, type = Type, payload = Payload}) ->
+    TypeBin = encode_type(Type),
+    <<Dst/binary, Src/binary, TypeBin:16, Payload/binary>>.
+
+%%--------------------------------------------------------------------
+%% EtherType mapping
+%%--------------------------------------------------------------------
+
+decode_type(?ETH_ARP)  ->
+    {ok, arp};
+decode_type(?ETH_IPV4) ->
+    {ok, ipv4};
+decode_type(?ETH_IPV6) ->
+    {ok, ipv6};
+decode_type(?ETH_VLAN) ->
+    {ok, tagged_frame};
+decode_type(_) ->
+    error.
+
+encode_type(arp) ->
+    ?ETH_ARP;
+encode_type(ipv4) ->
+    ?ETH_IPV4;
+encode_type(ipv6) ->
+    ?ETH_IPV6;
+encode_type(tagged_frame) ->
+    ?ETH_VLAN.
+
+%%--------------------------------------------------------------------
+%% MAC helpers (对齐 Swift MacAddress)
+%%--------------------------------------------------------------------
+
+-spec is_broadcast_mac(binary()) -> boolean().
+is_broadcast_mac(<<255,255,255,255,255,255>>) ->
+    true;
+is_broadcast_mac(_) ->
+    false.
+
+-spec is_multicast_mac(binary()) -> boolean().
+is_multicast_mac(<<1,0,94,_/binary>>) ->
+    true;
+is_multicast_mac(_) ->
+    false.
\ No newline at end of file