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

Fred Stratton fredstratton at imap.cc
Thu Dec 19 06:32:11 EST 2013

On 19/12/13 11:31, Fred Stratton wrote:
> Presumably you want these changes for some future use of the interface 
> by a wider audience, rather than current users of ceroWRT.
> There is an requirement for this less sophisticated user to turn AQM 
> on for ADSL. There are far more ADSL users than those who use fibre or 
> cable.  In the UK, offered a choice, about only 25 per cent of ADSL 
> users migrate to fibre. The figure for cable is 10 per cent. This is 
> in a fairly open market with competition.
> I would argue that the default should be 'on'.
> You state the choice in the interface pull down should be 'ethernet or 
> 'atm'. Currently it is 'ethernet' or 'adsl', which semantically makes 
> more sense, even though it uses a mystic, undocumented tc-stab option, 
> namely 'adsl'.
> The 'adsl' option appears to work, which is why I advocate it.
> Finally, the fourth of these 3 comments...
> OpenWRT developers are working on the TP-LINK TD-W8970, a gateway 
> device containing a Lantiq SoC. The device is cheaper in Europe than 
> the US for a change.
> Lantiq apparently have open-sourced their code, and the device will be 
> able to connect to the internet via ADSL2 or VDSL2, extending its 
> capabilities.
> Your interface will need to be modified again for a gateway device, 
> rather than a router.
> On 19/12/13 10:49, Sebastian Moeller wrote:
>> Hi Rich,
>> On Dec 19, 2013, at 05:12 , Rich Brown <richb.hanover at gmail.com> wrote:
>>> Hi Sebastian,
>>>>> 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 :)
>>> Is this a challenge? Well, I accept! :-)
>>> http://www.bufferbloat.net/projects/cerowrt/wiki/Setting_up_AQM_for_CeroWrt_310 
>>> is a draft. I recycled the images from a previous message and wrote 
>>> the least amount that I could that is likely to be true.
>>     This is great, thanks a lot. I have made a few changes to the GUI 
>> yesterday, which hopefully improve the usability, so if the new GUI 
>> passes muster with the cerowrt crowd, the screenshots will need to 
>> change as you note on top.
>>> Please send me comments (or edit the page directly, if you have 
>>> permissions.)
>>     I do not have edit permissions, so I just comments here.
>> Basic settings:
>>     Why 85% as starting point? And can we give instructions how to 
>> measure "degradation in performance", so that non-technical users 
>> have a chance to actually optimize their own system?
>> Queueing Discipline:
>>     Maybe we can add a link to the mail list page 
>> (https://lists.bufferbloat.net/listinfo/cerowrt-devel)?
>>     Also can we note that it is recommended to turn ECN off for the 
>> egress, as we handle packets before the bottleneck and dropping 
>> packets actually allows us to send other more urgent packets , while 
>> on ingress it is recommended to turn ECN on, as the packets have 
>> cleared the bottleneck already, and hence dropping has no bandwidth 
>> advantage anymore. Both dropping and ECN should have the same effect 
>> on TCP adaptation to the path capacity.
>> Link Layer Adaptation:
>>     I think the first question is: Do I have an ATM carrier between 
>> your modem and your ISP's DSLAM? This typically is true for all ADSL 
>> variants.
>>     The second question is: Do I have overhead on the link outside of 
>> Ethernet framing? This typically is true for users of PPPoE and 
>> PPPoATM and even Bridging I think.
>>     If the answer to any of these questions is yes, one needs to 
>> activate the link layer adaptations.
>>     In case of pure overhead select ethernet, in case of ADSL select 
>> ATM.
>>     Fill in the per packet overhead in byte (see: 
>> http://ace-host.stuart.id.au/russell/files/tc/tc-atm/, 
>> http://web.archive.org/web/20100527024520/http://www.adsl-optimizer.dk/ 
>> and http://www.faqs.org/rfcs/rfc2684.html). If the overhead truly is 
>> zero and no ATM carrier is used, then select "none" for link layer 
>> adaptation. (I changed this page, so the tc_stab htb_private 
>> selection is under advanced options, and there is a selection of 
>> "none", "ethernet", and "none" in the first drop down box, "none" 
>> disables the link layer adaptation. Also the drop down box contains 
>> some information which selection is relevant for which cases).
>> What’s going on here? Why do I need this?:
>>     I think we should mention that only with the proper link layer 
>> selected and the overhead specified cerowrt is able to assess how 
>> large each packet is on the link to the ISP, and only then the 
>> shaping is deterministic. (For ATM users without the adaptations the 
>> shaper is stochastically too optimistic about the link capacity 
>> (which is too say the shaper is too optimistic about the effective 
>> packet sizes)).
>> Best Regards
>>     Sebastian
>>> Thanks.
>>> Rich
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