Exponential Backoff
For retransmission N (1<=N<=10)
- choose k at random on U(0..2^N-1)
- wait k * (51.2msec) to retransmit
- send on idle; repeat on another collision
- for (11<=N<=15), use U(0..1023)
- if N = 16, drop frame
Longer wait implies lower priority (strategy is not “fair”)