an arp packet:


                                     
                                f                  
                                rt    ht    pt   hs   ps
                                ay    ay    ry   ai   ri           sender   sender    target  target 
         ethernet    ethernet   mp    rp    op   rz   oz          ethernet    ip     ethernet   ip 
         dest addr   src addr   ee    de    te   de   te   op       addr     addr      addr    addr
       -----------------------------------------------------------------------------------------------
       |     6     |     6     |  2  |  2  |  2  | 1 | 1 |  2  |     6     |   4   |    6    |   4   |    
       -----------------------------------------------------------------------------------------------
       |        ethernet             |                        28 byte                                |
       |         header              |                   ARP request/reply                           |