- Fast retransmit: When 3 duplicate ACKs received, retransmit the packet presumed lost without waiting for timeout
- Fast recovery (implemented in TCP Reno): When TCP fast retransmits, instead of going into Slow start (CWND=1) like you would if it timed out, goes directly to congestion avoidance phase (halves CWND)
TCP Tahoe only has fast retransmit, Reno also has fast recovery
- Motivation: Prevent “pipe” from emptying after fast retransmit
- Idea: each DUP ACK represents a packet having left the pipe (successfully)