Fast Retransmit and Recovery
Goals:
- Timeout avoidance: The 500 ms timer granularity can have an adverse performance impact especially for high speed n/ws
- Selective retransmission: Especially when packets are dropped due to error or light congestion
- Fast Recovery: Converge quickly to a state of congestion avoidance (linear increase) with half-current window -- the assumed ideal window size.
Observation: Receivers are required to send an immediate duplicate acknowledgment when they receives out-of-order data segments.