To this end, we designed and implemented Gordon, a tool that allows us
to measure the exact congestion window (cwnd) corresponding to each successive RTT in the TCP connection
response of a congestion control algorithm. To compare a measured flow to the known variants, we created a
localized bottleneck where we can introduce a variety of network changes like loss events, bandwidth change,
and increased delay, and normalize all measurements by RTT.
An offline classifier is used to identify the TCP
variant based on the cwnd trace over time.