Congestion avoidance
- Increment cwnd by 1 per ack until ssthresh
- Increment by 1/cwnd per ack afterwards (“Congestion avoidance” or “linear increase”)
Idea: ssthresh estimates the bandwidth-delay product for the connection.
Initialization: ssthresh = Receiver window or default 65535 bytes. Larger values thru options.
If source is idle for a long time, cwnd is reset to one.