1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8  1 2 3 4 5 6 7 8
+----------------+----------------+----------------+----------------+
|      flags     |  authen_method |    priv_lvl    |  authen_type   |
+----------------+----------------+----------------+----------------+
| authen_service |    user_len    |    port_len    |  rem_addr_len  |
+----------------+----------------+----------------+----------------+
|    arg_cnt     |   arg_1_len    |   arg_2_len    |      ...       |
+----------------+----------------+----------------+----------------+
|   arg_N_len    |    user ...
+----------------+----------------+----------------+----------------+
|   port ...
+----------------+----------------+----------------+----------------+
|   rem_addr ...
+----------------+----------------+----------------+----------------+
|   arg_1 ...
+----------------+----------------+----------------+----------------+
|   arg_2 ...
+----------------+----------------+----------------+----------------+
|   ...
+----------------+----------------+----------------+----------------+
|   arg_N ...
+----------------+----------------+----------------+----------------+