[Codel] R: Jumbo frames with fq_codel

[Dave Taht]

On Mon, Nov 25, 2013 at 10:17 AM, Alessandro Bolletta
<alessandro at mediaspot.net> wrote:
>>On Mon, Nov 25, 2013 at 10:02 AM, Alessandro Bolletta <alessandro at mediaspot.net> wrote:
>> Hi guys,
>> I'm working on an environment which runs on jumbo ethernet frames (about 1550bytes) and I would ask you if do you think that it's needed >a trick in order to correctly debloat interfaces as ath9k and ag71xx which carries such big frames.
>
>>I am under the impression that the ag71xx does not support jumbo frames.
>>Slightly larger than usual frames? dunno.
>
> We are thinking to implement jumbo frames support on some devices based on ag71xx :)
> Many SoCs support up to 2028 bytes or 4076 bytes of MTU but the driver still can't manage MTUs higher than 1518bytes.

It sounds like you are going down the path I went down about 7 years
back in the WISP6 project. Back then I wanted to deliver a pure ipv6
backbone and encapsulate ipv4 traffic inside it at the normal 1500
MTU.

I built hardware that worked with larger MTUs, and encountered more
bugs in ipv6 encapsulation than I care to think about. Then I tried to
change hardware because the manufacturer had canceled the product and
ran into great difficulty finding a replacement.

For the record, that device was this one, which supported 2028 bytes or so:

http://www.embeddedarm.com/products/board-detail.php?product=TS-7250

>>the ath9k supports frames up to the size of the wireless standards (23xx bytes or so)
>
> Yes.
>
>>fq_codel's internal quantum is the actual ip packet size, not the wire size.
>>at lower bandwidths it pays to have a lower quantum (like 300) on outgoing interfaces.
>
>>In openwrt the default on all interfaces is 300, which I dont necessarily agree with.
>
> Ok. I thought that codel would leverage on layer-2 parameters, as the size of the ethernet frame.
>
>>
>> Thanks
>>
>> --
>> Alessandro Bolletta
>> Mediaspot S.r.l.
>>
>>
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>
>
>
> --
> Dave Täht
>
> Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html
>
>
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-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html