moeller0 at gmx.de
Sun Dec 8 14:02:26 EST 2013
On Dec 8, 2013, at 18:47 , Juliusz Chroboczek <jch at pps.univ-paris-diderot.fr> wrote:
>>> as long as you have fewer than 250 congestion-limited flows at
>>> a given time.
>> Currently not doing much of anything my router has 142 active
>> connections (according to conntrack)
> 142 active conntrack entries, as opposed to congestion-limited flows.
> Roughly speaking, an active conntrack entry is a flow that has sent at
> least a packet within the last minute or so, while a congestion-limited
> flow is one that sends data as fast as it reasonably can. I certainly
> hope you don't have 142 congestion-limited flows on an idle router.
Well, I guess the crux of the problem is that even at 100Mbit/s with 250 packets (according to your estimate) we are not in the clear as we can only round robin 250 equally weighted queues, and much less at say 10Mbit/s uplinks. So opening around 90 tabs in a browser increased the number of connections to ~2000, all of them new, so all of them will be expedited by fq_codel. So I am still not convinced that real time critical applications will work well if the bottleneck does not do priority management even at 100Mbit/s.
>> I still think that for VoIP prioritizing might still be required
>> until supplied minimum bandwidth gets higher.
> I agree, in the short term. In the medium term, I'm optimistic we can
> get rid of these nasty hacks, which is why I'd rather see Dave spend
> his copious free time on something else.
I fully agree about Dave's time :).
About prioritizing, I am less optimistic as I can not see how the system can behave well under extreme load; I for one would be quite unhappy if an device on my internal network could effectively DOS my ability to make phone calls (I switched to IP telephony so this theoretical issue has become practical for me).
Or put it that way, I hope that the core internet is over-provided and will not cause congestion, at the same time I want to be able to max out my internet connection and still be able to phone.
>> Even at 1000 symmetric I still think it would be a good idea to
>> isolate really latency critical traffic from the rest,
> It would certainly be good to have hard data rather than confronting
> your intuitions with my back-of-the-envelope computations. (Hint, hint.)
I guess I will chime in again once I have symmetric 1000Mbit/s link then :) I guess until I have an internet connection I cannot easily saturate I will stubbornly stick to my conviction that some sort of hard polity system is needed, until convinced by data :)
> -- Juliusz
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