[Starlink] FQ_Codel

[David Lang]

On Wed, 8 Jun 2022, Dave Taht wrote:

> On Wed, Jun 8, 2022 at 5:21 PM David Lang <david at lang.hm> wrote:
>>
>> multiple access points, good. Mesh can make the problem worse.
>>
>> The combination of hidden transmitters (station in the middle can hear stations
>> on both ends, but they can't hear each other and so step on each other) and just
>> more airtime needed ro relay the messages as there are more hops can make the
>> congestion worse (however, it is possible that higher data rates could make the
>> transmissions shorter, but since the inter-aggregate gaps and per-aggregate
>> headers are fixed at a low data rate, I doubt that it works that way in
>> practice)
>>
>> but get a few additional APs hooked together via wires, and you have a clear win
>> that scales very well. It's what we do at the Scale conf with 100+ APs to
>> support 3k+ geeks.
>
> Is there a physical scale conference this year? (It's in LA and a lot
> of space/film folk go there)

yes, it got pushed from the beginning of the year and will not be the last 
weekend of July

> For those that don't know, david lang has been putting together the
> fq_codeled APs there for what? 8 years now? Conference feedback on the
> wifi has generally been uniformly positive.

I've been doing the wifi since 2009 and am now co-chair for the network team.

> What APs do you use now?

We are back in the LAX hilton this year, our network is ~50 juniper 4200 
switches, 100+ wndr2700/3800s and several miles of cable and a pair of fairly 
beefy servers to run the VMs to run and monitor the network. We've been talking 
the last 4-5 years of replacing the APs with something newer, but a combination 
of a turnover of most of our tech staff, covid, and the unreliability of the 
drivers on our first pick has kept us pushing it back year by year (when you are 
going to buy 100+ APs it adds up to quite a price tag, especially for an 
all-volunteer event)

Over the last couple of years we've setup a couple of the 3800s hooked to a pi 
and a couple relays so every build gets auto-flashed and tested and just 
finished setting up a system that lets us put a hub/switch in place and flash 
the APs to the current version by the DHCP server detecting them come up on the 
network.

This year we will be doing an updated version of what I documented here 
https://www.usenix.org/conference/lisa12/technical-sessions/presentation/lang_david_wireless
but with an even higher density of APs on low power (the walls in this hotel are 
pretty good shielding and more people have 5G than did 10 years ago)

If anyone is in the area, stop by and chat. We are always looking for volunteers 
to help setup and teardown as well ;-) (setup starts monday, and the guy who 
was going to be running monitoring just had to back out if someone wants to 
jump in the deep end)


David Lang

>> David Lang
>>
>> On Wed, 8 Jun 2022, Stuart Cheshire wrote:
>>
>>> On 8 Jun 2022, at 12:12, warren ponder <wponder11 at gmail.com> wrote:
>>>
>>>> So this is really helpful. Is it fair to say then that end users with SQM and fq_codel on a Starlink connection should essentially not turn on SQM.and.just leave it off?
>>>
>>> My advice is that people should have SQM (e.g., fq_codel) enabled anywhere it is available. For devices that aren’t the bottleneck hop on a path it won’t make any difference, but it won’t hurt. And if the network topology is such that it does become the bottleneck hop, even briefly, SQM will avoid having a big queue build up there.
>>>
>>> One example is Wi-Fi. If you have 50Mb/s Internet service and 802.11ac Wi-Fi in the house, your Wi-Fi is unlikely to be the bottleneck. But if you walk out to the garden and the Wi-Fi rate drops to 40Mb/s, then suddenly bufferbloat in the AP can bite you, leading to bi-modal network usability, that abruptly falls off a cliff the moment your Wi-Fi rate drops below your Internet service rate. I think this is a large part of the reason behind the enthusiasm these days for “mesh” Wi-Fi systems -- you need to blanket your home with sufficient density of Wi-Fi access points to ensure that they never become the bottleneck hop and expose their incompetent queue management. If you get 11Mb/s in the garden that should be plenty to stream music, but throw in some egregious bufferbloat and a perfectly good 11Mb/s rate becomes unusably bad. Ironically, if you pay more for faster Internet service then the problem gets worse, not better, because the effective usable range of your bufferbloa
 te
>>  d Wi-Fi access points shrinks as the rate coming into the house goes up.
>>>
>>> Stuart Cheshire
>>>
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