3. Congestion Control Algorithms
This section defines the four congestion control algorithms: slow start, congestion avoidance, fast retransmit, and fast recovery, developed in [Jac88] and [Jac90].
General Principles
In some situations, it may be beneficial for a TCP sender to be more conservative than the algorithms allow; however, a TCP MUST NOT be more aggressive than the following algorithms allow (that is, MUST NOT send data when the value of cwnd computed by the following algorithms would not allow the data to be sent).
Also, note that the algorithms specified in this document work in terms of using loss as the signal of congestion. Explicit Congestion Notification (ECN) could also be used as specified in [RFC3168].