diff --git a/lib/openflow/multipart/aggregate/reply.ex b/lib/openflow/multipart/aggregate/reply.ex
index dfecbf0..0dadfa1 100644
--- a/lib/openflow/multipart/aggregate/reply.ex
+++ b/lib/openflow/multipart/aggregate/reply.ex
@@ -44,7 +44,7 @@ defmodule Openflow.Multipart.Aggregate.Reply do
     }
   end
 
-  @spec to_binary(t()) :: <<_::192>>
+  @spec to_binary(t()) :: <<_::64, _::_*8>>
   def to_binary(aggregate) do
     <<
       Openflow.Multipart.Reply.header(aggregate)::bytes,
diff --git a/lib/openflow/multipart/desc/reply.ex b/lib/openflow/multipart/desc/reply.ex
index a995cf2..20158e5 100644
--- a/lib/openflow/multipart/desc/reply.ex
+++ b/lib/openflow/multipart/desc/reply.ex
@@ -15,22 +15,70 @@ defmodule Openflow.Multipart.Desc.Reply do
 
   alias __MODULE__
 
+  @type t :: %Reply{
+          version: 4,
+          datapath_id: String.t() | nil,
+          aux_id: 0..0xFF | nil,
+          xid: 0..0xFFFFFFFF,
+          flags: [],
+          mfr_desc: String.t(),
+          hw_desc: String.t(),
+          sw_desc: String.t(),
+          serial_num: String.t(),
+          dp_desc: String.t()
+        }
+
   @desc_str_len 256
   @serial_num_len 32
 
+  @spec ofp_type() :: 19
   def ofp_type, do: 19
 
-  def read(
-        <<mfr_desc::size(@desc_str_len)-bytes, hw_desc::size(@desc_str_len)-bytes,
-          sw_desc::size(@desc_str_len)-bytes, serial_num::size(@serial_num_len)-bytes,
-          dp_desc::size(@desc_str_len)-bytes>>
-      ) do
+  @spec new(
+          xid: 0..0xFFFFFFFF,
+          mfr_desc: String.t(),
+          hw_desc: String.t(),
+          sw_desc: String.t(),
+          serial_num: String.t(),
+          dp_desc: String.t()
+        ) :: t()
+  def new(options \\ []) do
     %Reply{
-      mfr_desc: Openflow.Utils.decode_string(mfr_desc),
-      hw_desc: Openflow.Utils.decode_string(hw_desc),
-      sw_desc: Openflow.Utils.decode_string(sw_desc),
-      serial_num: Openflow.Utils.decode_string(serial_num),
-      dp_desc: Openflow.Utils.decode_string(dp_desc)
+      xid: options[:xid] || 0,
+      mfr_desc: options[:mfr_desc] || "",
+      hw_desc: options[:hw_desc] || "",
+      sw_desc: options[:sw_desc] || "",
+      serial_num: options[:serial_num] || "",
+      dp_desc: options[:dp_desc] || ""
+    }
+  end
+
+  @spec to_binary(t()) :: <<_::64, _::_*8>>
+  def to_binary(%Reply{} = desc) do
+    <<
+      Openflow.Multipart.Reply.header(desc)::bytes,
+      String.pad_trailing(desc.mfr_desc, @desc_str_len, <<0>>)::bytes,
+      String.pad_trailing(desc.hw_desc, @desc_str_len, <<0>>)::bytes,
+      String.pad_trailing(desc.sw_desc, @desc_str_len, <<0>>)::bytes,
+      String.pad_trailing(desc.serial_num, @serial_num_len, <<0>>)::bytes,
+      String.pad_trailing(desc.dp_desc, @desc_str_len, <<0>>)::bytes
+    >>
+  end
+
+  @spec read(<<_::8448>>) :: t()
+  def read(<<
+        mfr_desc::size(@desc_str_len)-bytes,
+        hw_desc::size(@desc_str_len)-bytes,
+        sw_desc::size(@desc_str_len)-bytes,
+        serial_num::size(@serial_num_len)-bytes,
+        dp_desc::size(@desc_str_len)-bytes
+      >>) do
+    %Reply{
+      mfr_desc: hd(String.split(mfr_desc, <<0>>, parts: 2)),
+      hw_desc: hd(String.split(hw_desc, <<0>>, parts: 2)),
+      sw_desc: hd(String.split(sw_desc, <<0>>, parts: 2)),
+      serial_num: hd(String.split(serial_num, <<0>>, parts: 2)),
+      dp_desc: hd(String.split(dp_desc, <<0>>, parts: 2))
     }
   end
 end
diff --git a/lib/openflow/multipart/desc/request.ex b/lib/openflow/multipart/desc/request.ex
index f0b17c5..999968e 100644
--- a/lib/openflow/multipart/desc/request.ex
+++ b/lib/openflow/multipart/desc/request.ex
@@ -4,22 +4,28 @@ defmodule Openflow.Multipart.Desc.Request do
     xid: 0,
     # virtual field
     datapath_id: nil,
+    aux_id: nil,
     flags: []
   )
 
   alias __MODULE__
 
+  @type t :: %Request{
+          version: 4,
+          datapath_id: String.t(),
+          aux_id: 0..0xFF | nil,
+          xid: 0..0xFFFFFFFF
+        }
+
+  @spec ofp_type() :: 18
   def ofp_type, do: 18
 
-  def new(xid \\ 0) do
-    %Request{xid: xid}
-  end
+  @spec new(0..0xFFFFFFFF) :: t()
+  def new(xid \\ 0), do: %Request{xid: xid}
 
-  def read("") do
-    %Request{}
-  end
+  @spec read(<<>>) :: t()
+  def read(""), do: %Request{}
 
-  def to_binary(%Request{} = msg) do
-    Openflow.Multipart.Request.header(msg)
-  end
+  @spec to_binary(t()) :: <<_::64>>
+  def to_binary(%Request{} = msg), do: Openflow.Multipart.Request.header(msg)
 end
diff --git a/test/lib/openflow/ofp_desc_stats_test.exs b/test/lib/openflow/ofp_desc_stats_test.exs
new file mode 100644
index 0000000..f732979
--- /dev/null
+++ b/test/lib/openflow/ofp_desc_stats_test.exs
@@ -0,0 +1,41 @@
+defmodule OfpDescTest do
+  use ExUnit.Case
+
+  describe "Openflow.Multipart.Desc.Request" do
+    test "with default values" do
+      desc = Openflow.Multipart.Desc.Request.new(0)
+
+      desc
+      |> Openflow.to_binary()
+      |> Openflow.read()
+      |> Kernel.elem(1)
+      |> Kernel.==(desc)
+      |> assert()
+    end
+  end
+
+  describe "Openflow.Multipart.Desc.Reply" do
+    test "with default values" do
+      desc =
+        %Openflow.Multipart.Desc.Reply{
+          dp_desc: "None",
+          hw_desc: "Open vSwitch",
+          mfr_desc: "Nicira, Inc.",
+          serial_num: "None",
+          sw_desc: "2.11.0"
+        }
+        |> Map.to_list()
+        |> Openflow.Multipart.Desc.Reply.new()
+        |> Openflow.to_binary()
+        |> Openflow.read()
+        |> Kernel.elem(1)
+
+      assert desc.xid == 0
+      assert desc.mfr_desc == "Nicira, Inc."
+      assert desc.dp_desc == "None"
+      assert desc.hw_desc == "Open vSwitch"
+      assert desc.sw_desc == "2.11.0"
+      assert desc.serial_num == "None"
+    end
+  end
+end