diff --git a/applications/arts/designs/arts_unb1_sc1/src/vhdl/arts_unb1_sc1_output.vhd b/applications/arts/designs/arts_unb1_sc1/src/vhdl/arts_unb1_sc1_output.vhd
index d56173b15508c9964787bdbcabf97e33fe0915c0..dcadb8df239e1694068de7801ea5efbcc8d09165 100644
--- a/applications/arts/designs/arts_unb1_sc1/src/vhdl/arts_unb1_sc1_output.vhd
+++ b/applications/arts/designs/arts_unb1_sc1/src/vhdl/arts_unb1_sc1_output.vhd
@@ -73,6 +73,8 @@ ARCHITECTURE wrap OF arts_unb1_sc1_output IS
   CONSTANT c_nof_hdr_fields : NATURAL :=           1 +   3 + 12 +   4 +  6 + 8 ;    -- 34 fields
                      -- Numer of bytes:            2 + <-----42-----> + 16 + 8*24/8 -- 2 + 42 + 40 = 84 bytes = 672 bits
 
+  -- ip_total_length = 4800 (application payload) + 24 (flag header) + 16 (id header) + 8 (udp header) + 20 (ip header) = 4868
+
   CONSTANT c_hdr_field_arr  : t_common_field_arr(c_nof_hdr_fields-1 DOWNTO 0) := ( ( field_name_pad("word_align"                          ), "  ", 16, field_default(0) ),
                                                                                    ( field_name_pad("eth_dst_mac"                         ), "  ", 48, field_default(x"1418774428B8") ),
                                                                                    ( field_name_pad("eth_src_mac"                         ), "  ", 48, field_default(0) ),