Essentially the same as for NAKACK: instead of adding every message to the retransmitter and creating 1 timer task for it, we create SeqnoRanges in increments of (say) 1000 messages. SeqnoRange #1 is 1-1000, #2 is 1001-2000 and so on.

Every SeqnoRange has a low and a high, e.g. lo=1 and high=1000. However, we only retransmit messages with their bit set to 0 from low to bits.length: if we added messages 1-100 to the first range, then low=1, length=100 and high=1000. We only retransmit from 1-100.

This creates 1 task in the timer for 1000 messages, instead of 1000 tasks ! When adding a new message (e.g. 101), length() gets automatically adjusted, so retransmission will include 1-101 (only the 0 bits of course).