Per RFC9438, sec 4.8, t_epoch is supposed to remain
the time since the current congestion avoidance
phase - presumably prior to the RTO.

However, doing so will result in an extremely inflated value
when ACKs are processed, since the RTO may be many orders of
magnitude higher than a typical RTT (e.g. 15 sec vs 0.1 ms),
especially when there are multiple RTOs with exponential
backoff after another.

In that case, cwnd can jump to exteme values with the
next received ACK - up to the full receive window, and
TSO can burst massive traffic into the network.

use siftr to monitor the evolution of cwnd across
a longer period of packet discards; once slow-
start is over, cwnd jumps up dramatically.