[Codel] [RFC PATCH] codel: ecn mark at target

Eric Dumazet eric.dumazet at gmail.com
Sun Aug 5 01:30:23 EDT 2012

On Sat, 2012-08-04 at 20:06 -0700, Andrew McGregor wrote:
> Well, thanks Eric for trying it.
> Hmm.  How was I that wrong?  Because I was supporting that idea.
> Time to think.

No problem Andrew ;)

Its seems ECN is not well enough understood.

ECN marking a packet has the same effect for the sender : reducing cwnd
exactly like a packet drop. Only difference is avoiding the

It cannot be used only to send a 'small' warning, while other competing
non ECN flows have no signal.

As far as packet schedulers are concerned, there should be no difference
in ECN marking and dropping a packet. I believe linux packet schedulers
are fine in this area.

Now, there are fundamental issues with ECN itself, out of Codel scope,
thats for sure.

How widely has been RFC 3540 deployed, anybody knows ?

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