[ns] ECN enabling

[Davide]

hi,

i'm using tcp reno and i want to turn on the ecn_ feature. i'm using
all module that don't use this information (the queue are all drop
tail) and only one module can set this flag.

to enable ecn i used this function

Agent/TCP set ecn_ 1

and even if my module don't send any ecn notification the result of
the simulation are totally different from the case with disabled ecn

there is something else that i have to know?
i've also took a look inside the test suite but in that case the ecn
notification are generated from the RED queue management

any help appreciated

Davide