Slow Start

Initially, $cwnd=1\cdot MSS$.

Then, $cwnd\times 2$ every RTT, implemented by incrementing cwnd by MSS on receipt of every ACK.

When $cwnd\geq ssthresh$, $cwnd + (MSS\cdot\frac{MSS}{cwnd})$ on receipt of every ACK within RTT.

$ssthresh$ is defined as $\frac{1}{2}cwnd$ at the last loss event.