The repair server maintains an ordered list of {HEAD ~ the retransmit servers} that are most likely to have buffered {TAIL ~ copies} of packets missing from the session 
The repair server maintains an ordered list of { HEAD ~ the retransmit servers } that are most likely to have buffered { TAIL ~ copies } of packets missing from the session
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH