The combination of the FEC value 515, the data block 500A, the FEC value 515′ and the data block 500A′ is the adaptive response 505A by the retransmit server {HEAD ~ 110A} to {TAIL ~ the repair server} 120A 
The combination of the FEC value 515 , the data block 500A , the FEC value 515′ and the data block 500A′ is the adaptive response 505A by the retransmit server { HEAD ~ 110A } to { TAIL ~ the repair server } 120A
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH