0             8             16
+---------------------------+
|Protocol name length = 4   |
+---------------------------+
|     'M'            'Q'    |
+---------------------------+
|     'T'            'T'    |
+---------------------------+
|Proto.level=5|Connect flags|          
+---------------------------+
|        Keep alive         |
+---------------------------+
| CONNECT Properties Length |
|      (up to 4 bytes)      |
+---------------------------+ 
| ( ..Other properties..)   |
+---------------------------+
|  Authentication Method    |
|      (0x15)  |   Len      |
|      Len     |   'a'      | 
|      'c'     |   'e'      |
+---------------------------+
|  Authentication Data      |   
|     (0x16)   |    Len     |
|      Len     |   token    | 
|  or token + PoP data      |
+---------------------------+