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

Thu Dec 19 08:35:55 EST 2013

On 19/12/13 13:13, Sebastian Moeller wrote:
> Hi Fred,
>
>
> On Dec 19, 2013, at 12:32 , Fred Stratton <fredstratton at imap.cc> wrote:
>
>> On 19/12/13 11:31, Fred Stratton wrote:
>>> 3 comments.
>>>
>>> Presumably you want these changes for some future use of the interface by a wider audience, rather than current users of ceroWRT.
> 	Oh, my goal is not so much "world domination" but rather making the link layer adjustments first class citizens in cerowrt's guy; if this should make it into openWRT I would not be unhappy, but it is not one of my personal goals.
I suspect all your work will end up in openWRT.
>>> 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'.
> 	Ah, the DSL users really do need to set the right overhead as well for the link layer adaptation to work well, otherwise the padding of the packet due to the quantization is wrong (not a total loss if the number of packets is large enough this could/should average out). So I am not sure whether default on will lead to happiness all around.

OK, I now understand your reasoning.
>
>>> 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 'adel'.
> 	Well, I changed it to ATM in the last version, as that is what is relevant for the link layer. So if in the future ADSL3 uses PTM we do not care :) Adel, did I write that? If so I can assure you I intended to write ADSL in lower case, it is just my on-line spell checker that corrects me badly...

OK, if the choice is between 'ethernet' and one renamed option.
>
>>> The 'adsl' option appears to work, which is why I advocate it.
> 	for tc and the kernel atm and adsl are the same, just two different names for the same thing. I think we should use ATM instead of ADSL for reasons hinted at above.
>   
>>> 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.
> 	Cheaper is good, but the other specs do not seem to exciting, 64MB ram 8Mb rom, only 2.4GHz radio (given the flakiness of both 2.4 and 5GHz I think it nice to have options :) )
>
>>> 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.
> 	What is the difference between a gateway device and a router?

A gateway also contains an internal 'modem'. The TD-W8970 has been 
chosen because it uses a Lantiq SoC. The TD-W8980 has all the features 
you desire, but with a Trendchip SoC, and so is of no use for openWRT.
>
> Best Regards
> 	Sebastian
>
>>>
>>> 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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