Lower bound for congestion window (drops or classic ECN)

[goelvidhi]

Markku Kojo said,

The draft modifies RFC 3168 when ECE arrives and would result
in cwnd < 2 MSS by setting a lower bound of 2 MSS for cwnd (only
ssthresh is supposed to have a lower bound of 2 MSS).
This is in conflict with RFC 3168, RFC 5033, and RFC 2914 which
require "full backoff", that is, a sender must continue decreasing
sending rate as long as congestion persists. This is a fundamental
property for any congestion control mechanism. For ECN, RFC 3168
(sec 6.1.2) requires that cwnd is halved until the minimum cwnd
of one MSS is received, and then the sender continues reducing
sending rate by using a timer with exponential backoff, if more
ECE-echo packets keep on arriving.

This implementation bug has been long with Linux and is present
in other stacks as well and should get corrected ASAP with
appropriate advise in all published RFCs, instead of replicating
the bug in the RFC series.

[larseggert]

Where are we with this one?