Re: [Bloat] sigcomm wifi

[David Lang <david@lang.hm>]

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On Wed, 20 Aug 2014, Jim Gettys wrote:

> On Wed, Aug 20, 2014 at 3:12 AM, Eggert, Lars <lars@netapp.com> wrote:
>
>> On 2014-8-19, at 18:45, Dave Taht <dave.taht@gmail.com> wrote:
>>> I figured y'all would be bemused by the wifi performance in the sigcomm
>>> main conference room this morning...
>>>
>>> http://snapon.lab.bufferbloat.net/~d/sigcomm_tuesday.png
>>
>> There is a reason we budgeted a 1G uplink for SIGCOMM Helsinki and made
>> sure we had sufficient AP coverage...
>>
>
> ​And what kinds of AP's?  All the 1G guarantees you is that your bottleneck
> is in the wifi hop, and they can suffer as badly as anything else
> (particularly consumer home routers).
>
> The reason why 802.11 works ok at IETF and NANOG is that:
>  o) they use Cisco enterprise AP's, which are not badly over buffered.  I
> don't have data on which enterprise AP's are overbuffered.
>  o) they do a good job of placing the AP's, given a lot of experience
>  o) they turn on RED in the router, which, since there is a lot of
> aggregated traffic, can actually help rather than hurt, and keep TCP
> decently policed.
>  o) they play some interesting diffserv marking tricks to prioritize some
> traffic, getting part of the effect the fq_codel gives you in its "new
> flow" behavior by manual configuration.  Fq_codel does much better without
> having to mess around like this.
>
> Would be nice if they (the folks who run the IETF network) wrote a BCP on
> the topic; I urged them some IETF's ago, but if others asked, it would help.
>
> If you try to use consumer home routers running factory firmware and hack
> it yourself, you will likely lose no matter what you backhaul is (though
> you might do ok using current CeroWrt/OpenWrt if you know what you are
> doing.

Yep, bad AP setup, coverage and configuration can cripple you.

how many people in the room?

David Lang

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