This is the idea of using the ECN-Nonce (in the no-congestion case) to detect spurious loss events, documented in:
Michael Welzl: "Using the ECN Nonce to detect Spurious Loss Events in
TCP", IEEE Globecom 2008, 30 November - 4 December
2008, New Orleans, LA USA.
which is based on Thomas Raffler's master thesis on this topic:
Here is the code that he used, including a ns-2.29 directory which was changed
as described in the thesis: 
The next step will be to develop and test the idea with real-life code, for which Armin Abfalterer wrote an updated implementation of the ECN Nonce for Linux (kernel 2.6.29.6): patch and module