Hello!
> The short question: Does the Linux TCP implementation support the ECN
> timeout suggested in rfc2481?
No.
> Without this mechanism, one should need an (MSS * num_of_connections)
> size txbuffer on a bottleneck link to totally avoid packet losses even
> when marking every packet with ECN CE. :(
Grr... goal of ECN is not "avoiding of losses", its goal is preservation
of ACK clock in presence of congestion. Artificial timeout has nil impact
comparing to normal timeout.
Note also one more thing (which makes threshold twice worse and, probably,
should be changed unlike above): we do not allow to drop cwnd under 2 segments
without real losses. The reason is the same: dropping cwnd under 2 segments
also breaks ACK clock due to delacks and therefore it is unacceptable.
Alexey
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