[Cerowrt-devel] cerowrt-3.10.24-5 dev build released

Sebastian Moeller moeller0 at gmx.de
Wed Dec 18 17:43:13 EST 2013

Hi Rich,

On Dec 18, 2013, at 14:58 , Rich Brown <richb.hanover at gmail.com> wrote:

> I like David Lang’s questions:
> 1) If we had “full knowledge” of the customer’s link, how many different cases would we have to take into account?
> 2) What happens if we get it wrong?
> And I think I understand Sebastian Moeller’s answers:
> 1) People using ATM-based carriers need the ATM link layer adaptation calculation; others (PTM, Cable, Fiber, etc.) don’t need that calculation.

	Except even with PTM or Fiber there still might be the need to specify an overhead (e.g. 8 bytes for PPPoE) in this case one needs to select the "ethernet" link layer...

> 2) Getting it wrong hurts in each case, but it seems worse where people are using PTM or Ethernet-based links since they lose 10% of their bandwidth due to the 48 in 53 bytes encapsulation. Failure to use the ATM calculation over an ATM-based link makes VoIP etc. less good and fails to make CeroWrt stand out as a great solution, but it’s the status quo for the entire world.

	Or we could say, the default should be ATM so that the ATM latency is under control again, while PTM users just sacrifice some (considerable) amount of bandwidth :)

> If the choices are as “simple” as this (and please correct me if I’m wrong :-) we really want to find a way to encourage people to use the ATM calculation when it’s warranted. We could hope that they find their way to the AQM tab (before their eyes glaze over), but that seems too big a hurdle.

	So I changed the link layer tab a bit, hopefully making clearer which link layer to select...

> Perhaps we could extend the Interface configuration page to add a “Link uses DSL/ADSL:” checkbox right below the Protocol dropdown. Default would be off, but when customers go to the GE00 interface to enter their PPPoE/PPPoATM/ISP credentials, they’d see this additional checkbox. Checking it would feed that info to the AQM tab. (And perhaps there could be a link there either to the AQM tab, or to the wiki for more information.)

	I am happy to include a link to a wiki, but I guess we first need a wiki page :) 


> Best,
> Rich

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