Cumulative and Delayed ACKs
Cumulative ACK Example:
- receiver receives packets 1,2,3,5,6,7,8
- sends ACKs for 1,2,3 or maybe 1,2,3,3,3,3,3
- upon receiving packet 4, ACKs 8
Observations:
- can’t ACK out-of-order packets
- can delay ACKs, say, for every other packet
- delaying might be useful for piggybacking ACKs on data (on reverse-direction flow)