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

[Kathleen Nichols]

So you want to provide an incentive to deploy ECN. This also provides an
incentive to
scam the network. I think a bigger question is what is gained by doing
this? Is it more
important to deploy something called ECN than to have a well-functioning
network?

	Kathie

On 8/5/12 9:53 AM, Andrew McGregor wrote:
> Well, there's a lot of people at the IETF who really want to do other things with ECN, but it seems like the simple version is far too aggressive.
> 
> So, I think the desirable properties are something like:
> 1) Allow ECN flows to achieve the same or slightly higher throughput to maintain an incentive to deploy it.
> 2) Still drop ECN flows eventually to avoid too much queue buildup.
> 3) Account somehow for the fact that marking takes longer to control the queue (but we don't know how much longer).
> 
> Maybe mark ECN instead of dropping, but if we end up trying to mark/drop twice in one round, drop the later packets?
> 
> Oh, and ECN nonce deployment is negligible, to the extent that there are proposals in the IETF to reuse the bits for other things, and there is no pushback on that.
> 
> Andrew
> 
> On 4/08/2012, at 10:30 PM, Eric Dumazet <eric.dumazet at gmail.com> wrote:
> 
>> 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
>> retransmit[s].
>>
>> 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 ?
>>
>>
>>