[Codel] [Cake] Proposing COBALT

[moeller0]

Hi Jonathan,


> On Jun 4, 2016, at 16:16 , Jonathan Morton <chromatix99 at gmail.com> wrote:
> 
> 
>> On 4 Jun, 2016, at 17:01, moeller0 <moeller0 at gmx.de> wrote:
>> 
>> Maybe cake should allow to switch from the default mark by ECN policy to mark by drop per command line argument? At least that would allow much easier in the field testing… As is there is only the option of disabling ECN at the endpoint(s)…
> 
> I consider ignoring ECN in the way I described to be a fault condition inevitably resulting in unresponsive traffic.  As a fault condition, it should be rare.

	Operative word being “should” in my opinion; as long as we have no reliable statistics either way, assuming rarity seems overly optimistic to me. Not giving the user control over policy requires the default policy to be almost 100% applicable., here we have a demonstrated case where this requirement seems violated. Make out of that what you want, if cake were my project I would make ECN versus drop configurable at the qdisc, as the control via the endhosts seems comparatively tedious, especially for quick comparative testing. But cake is not my project, so all I can do is try to make a case for introducing a policy control toggle…

> 
> The main effect in practice is that the RTT for the affected flows grows well beyond normal, but since they are bulk transfers,
> this has only a minor detrimental effect (much of which is incurred sender-side in the form of retransmission buffers two orders of magnitude larger than necessary).
> 
> Rather than further complicate Codel or Cake, I’d like to simply apply a general solution for unresponsive traffic, ie. COBALT.

	If adding a toggle for ECN versus drop is your only concern in the complexity of cake’s configuration you have not been reading my arguments regarding the labyrinthian overhead keywords… Really not exposing this control for this might actually be a reasonable thing to do, but trying to “blame” this on added complexity seems far fetched… but what do I know…

Best Regards
	Sebastian

> 
> - Jonathan Mortob
>