Slow Start and Congestion Avoidance (continued)
Upon congestion (duplicate ACKs or time-out), the algorithm kicks back in.
- A comparison is made between the congestion window size and the advertised window size
- Whichever is smaller, is halved and saved as the slow-start threshold
- The value must be at least 2 segments unless the congestion was a time-out and then the congestion window is set to 1 (slow start)
- The TCP sender can start up in slow start or congestion avoidance
If the congestion value matches (or is greater than) the value in slow-start threshold, the congestion avoidance algorithm starts; otherwise, slow start is brought up.
Upon receipt of ACKs, the congestion window is increased.
Allows for a more linear growth in transmission rate.