From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr1-x42c.google.com (mail-wr1-x42c.google.com [IPv6:2a00:1450:4864:20::42c]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 000333B29E for ; Tue, 6 Oct 2020 09:10:10 -0400 (EDT) Received: by mail-wr1-x42c.google.com with SMTP id m6so13426239wrn.0 for ; Tue, 06 Oct 2020 06:10:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=ieee.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cjkkTB3OYTEskpeacpIF9358Z3imO6SqrqxsK2mD26Y=; b=DbwTPe6SfPYVu2tluq+e1ZX37EQMH0PX7nSaqzGYVrllD3G72oGjmfjfAUGq10tS54 OL2fq8EtCU4ZA40jgplriLFyuCi0dnyfD1k2W3OK2ceMiC0z4JS0OLsKZ8+H0pZQq61b sRTUc0IYXCLs59UNgbHzHciH93E4JhzbCw4VE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=cjkkTB3OYTEskpeacpIF9358Z3imO6SqrqxsK2mD26Y=; b=fnBk/VZq1tIqjM6SGMxEsJ/I1Y+b4nGD5SfnWG7uq2HmuG71RhjEwtUQYs3bgISrip NHYu4SFjQAIWkk7QSLrVLCRG506qWAHHszfAlk1AXuG5anOH7MpmaLOMayL/hxhyYlSX u9zGdfx3coD/Y7V9Y99/OK+YH5owprE8+tq/H3Fknbe4FzIjGzgrl5j72B3kQjKZA8g9 ASNUFuWQqC+OOfbFIBs4l+PEjadAXo3NNiNUaLNp5+GgNfk59m+FhWezr+cwd8I65CUB Kit9Q3gs/ShmsAYhCYDglCLuF1knQo5F8g1nLPzW/3x2xG2UHkU4t0bgnVMYQvM+WDar WCJA== X-Gm-Message-State: AOAM531tbc2HnMJAv4FbazapzNmRCZCSLbSUkBvc4RpDrmhKBz11DXSF 3G0HvyHFgfDKoPEVfBX85dwEr5UV5RVs+bK4CTu6NA== X-Google-Smtp-Source: ABdhPJzvCpoYnyXaQkYpjI1D9al44VPsckxGNi6IdhHjI1MHTsyFTRPlUsj5MXKZib16IFfKcukd1cJvMF2yPnTJqD0= X-Received: by 2002:adf:ce8e:: with SMTP id r14mr4834428wrn.257.1601989809955; Tue, 06 Oct 2020 06:10:09 -0700 (PDT) MIME-Version: 1.0 References: <87d01vfue4.fsf@toke.dk> In-Reply-To: From: Luca Muscariello Date: Tue, 6 Oct 2020 15:09:58 +0200 Message-ID: To: Michael Welzl Cc: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= , Make-Wifi-fast Content-Type: multipart/alternative; boundary="0000000000008e951105b1005125" Subject: Re: [Make-wifi-fast] Where is the bloat in WiFi? X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 06 Oct 2020 13:10:11 -0000 --0000000000008e951105b1005125 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Michael, In my case (WAN =3D GPON DL/UP 2Gbps/500Mbps) some devices are bottlenecked at the AP, others are bottlenecked at the switch, like my NAS which is multi-homed with 2 x 1GE ports to the switch. WAN downlink is hardly ever the bottleneck. However, backhaul links are 10GE and there may be congestion there depending on the level of over subscription. (From a container in the NAS) Server: ORANGE FRANCE - Paris (id =3D 24215) ISP: Orange Latency: 0.92 ms (0.03 ms jitter) Download: 935.31 Mbps (data used: 433.1 MB) Upload: 599.02 Mbps (data used: 645.4 MB) Packet Loss: 0.0% For a laptop connected to one AP (line of sight available) I get 500Mbps DL/UL speedtest. For the uplink it is hard to say if the bottleneck is the uplink of the router or one of the three APs, or the switch? At 5GHz no device goes below ~700Mbps (PHY) rate according to the WLC. My case is not really common now, but with fiber adoption growth and more people working from home I expect this to become more common. WMM helps with all the online meetings we do these days. For video end-points (like Cisco DX) I only use ethernet. With fiber growth in the home, investments in the backhaul become critical to keep up with demand. For xDSL the bottleneck is the WAN with high probability. Luca On Tue, Oct 6, 2020 at 2:15 PM Michael Welzl wrote: > Hi, and thanks for a quick answer! > > But, it's not quite what I was looking for.... see below: > > > On 6 Oct 2020, at 13:47, Toke H=C3=B8iland-J=C3=B8rgensen wrote: > > > > Michael Welzl writes: > > > >> Hi all, > >> > >> A simple question to y'all who spent so much time on Cake and things > >> ... in a household using WiFi, which buffer is usually bloated? Where > >> does the latency really come from? > >> > >> Is it: > >> 1. the access point's downlink queue, feeding into the WiFi network, > > > > This we mostly fixed, but only if you're on a recent OpenWrt with the > > right WiFi drivers. > > Well okay... I was curious about where the bottleneck is. I can translate > my question into: "if Cake is installed everywhere, where does it have th= e > most work to do?". > > > > Otherwise, this is a major source of latency *if* > > the WiFi link is faster than the downlink from the internet. > > Huh? Slower, you mean? > > > > This > > depends on both the internet connection and the current rate each WiFi > > station operates at, so it can vary wildly, and on very short time > > scales. > > Sure... I was asking for the "if" in your statement above - since this is > an operationally-oriented list: what do people see? What is the more comm= on > case? > > > >> 2. the modem's downlink queue, feeding into the access point, > > > > If your internet (downlink) connection is slower than your WiFi link, > > this is where you'll get the queueing. > > Yes sure :-) see above: I wanted to know what the more common case > is, in households that people on this list have dealt with. > > > >> 3. the modem's uplink queue, > > > > As above, but in the other direction - but as uplinks tend to be > > asymmetric, this direction is often more of a problem. > > > >> 4. the access point's uplink queue towards the modem (hm, that seems > >> silly, surely the AP-modem connection is fast... so perhaps, instead: > >> the queue in the host, as it wants to send data towards the access > >> point) > > > > Yeah, that would be in the host; but host drivers can suffer from sever= e > > bufferbloat as well, especially as rates drop (since the buffers are > > often tuned for the maximum throughput the device can deliver in > > best-case signal conditions). > > > >> or is it a combination of these? > > > > Usually it's a combination; especially since the WiFi capacity varies > > wildly with signal conditions (as devices move around relative to the > > AP), general link usage (more devices active mean less available > > capacity for each device, exacerbated by airtime unfairness), and > > interference. Also there are things like excessive retries causing HoL > > blocking. > > Man, what an academic answer! Makes me think you have a PhD, or > something! What *theoretically* can happen is not what I was fishing for > :-D > > > >> I guess that, with openwrt, Cake is operating on the queue that's > >> feeding the wifi network, as the modem's queue is out of its > >> control... so: is this where the bottleneck usually is? > > > > It certainly used to be; but as uplink connection speeds improve, the > > bottleneck moves to the WiFi link. > > Yessss, that's why I was asking.... > > > > The extent to which this happens > > depends on where you are in the world; personally I've been bottlenecke= d > > on the WiFi link ever since I got a fibre upstream (and with 802.11ax > > rates maxing at >1Gbps, maybe that'll change again?). > > THIS is what I was after :) one data point, cool - so far, so good... > > Cheers, > Michael > > _______________________________________________ > Make-wifi-fast mailing list > Make-wifi-fast@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/make-wifi-fast --0000000000008e951105b1005125 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi Michael,

In my case (WAN =3D GPON DL/UP 2Gbps/500Mbps) some devic= es are bottlenecked at the AP, others are
bottlenecked at the switch, like my NAS wh= ich is multi-homed with 2 x 1GE ports to the switch.
WAN downlink is hardly ever the= bottleneck. However, backhaul links are 10GE and there may be=C2=A0
<= div class=3D"gmail_default" style=3D"font-family:monospace">congestion ther= e depending on the level of over subscription.=C2=A0

(From a container in the NAS)
=

=C2=A0 =C2=A0 =C2=A0Server: ORANGE FRANCE - Paris (id =3D 24215)=
=C2=A0 =C2=A0 =C2=A0 =C2=A0 ISP: Orange<= /div>
=C2=A0 =C2=A0 Latency:=C2=A0 =C2=A0 =C2= =A00.92 ms=C2=A0 =C2=A0(0.03 ms jitter)
= =C2=A0 =C2=A0Download:=C2=A0 =C2=A0935.31 Mbps (data used: 433.1 MB)
<= div class=3D"gmail_default">=C2=A0 =C2=A0 =C2=A0Upload:=C2=A0 =C2=A0599.02 = Mbps (data used: 645.4 MB)
Packet Loss:= =C2=A0 =C2=A0 =C2=A00.0%

For a laptop connected to one AP (line of sight available= ) I get 500Mbps DL/UL speedtest.=C2=A0
For the uplink it is hard to say if the bottl= eneck is the uplink of the router or one of the three APs,
or the switch? At 5GHz n= o device goes below ~700Mbps (PHY) rate according to the WLC.

My case is not really co= mmon now, but with fiber adoption growth and more people working from
=
home I expect = this to become more common. WMM helps with all the online meetings we do th= ese days.
For video end-points (like Cisco DX) I only use ethernet.

With fiber growth in the hom= e, investments in the backhaul become critical to keep up with demand.

For xDSL the bott= leneck is the WAN with high probability.

Luca




On Tue, Oct 6, 2020 at 2:15 PM Michael Welz= l <michawe@ifi.uio.no> wrot= e:
Hi, and thank= s for a quick answer!

But, it's not quite what I was looking for.... see below:

> On 6 Oct 2020, at 13:47, Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> wrote:
>
> Michael Welzl <michawe@ifi.uio.no> writes:
>
>> Hi all,
>>
>> A simple question to y'all who spent so much time on Cake and = things
>> ... in a household using WiFi, which buffer is usually bloated? Wh= ere
>> does the latency really come from?
>>
>> Is it:
>> 1. the access point's downlink queue, feeding into the WiFi ne= twork,
>
> This we mostly fixed, but only if you're on a recent OpenWrt with = the
> right WiFi drivers.

Well okay... I was curious about where the bottleneck is. I can translate m= y question into: "if Cake is installed everywhere, where does it have = the most work to do?".


> Otherwise, this is a major source of latency *if*
> the WiFi link is faster than the downlink from the internet.

Huh? Slower, you mean?


> This
> depends on both the internet connection and the current rate each WiFi=
> station operates at, so it can vary wildly, and on very short time
> scales.

Sure... I was asking for the "if" in your statement above - since= this is an operationally-oriented list: what do people see? What is the mo= re common case?


>> 2. the modem's downlink queue, feeding into the access point,<= br> >
> If your internet (downlink) connection is slower than your WiFi link,<= br> > this is where you'll get the queueing.

Yes sure=C2=A0 :-)=C2=A0 =C2=A0 =C2=A0see above: I wanted to know what the = more common case is, in households that people on this list have dealt with= .


>> 3. the modem's uplink queue,
>
> As above, but in the other direction - but as uplinks tend to be
> asymmetric, this direction is often more of a problem.
>
>> 4. the access point's uplink queue towards the modem=C2=A0 =C2= =A0(hm, that seems
>> silly, surely the AP-modem connection is fast... so perhaps, inste= ad:
>> the queue in the host, as it wants to send data towards the access=
>> point)
>
> Yeah, that would be in the host; but host drivers can suffer from seve= re
> bufferbloat as well, especially as rates drop (since the buffers are > often tuned for the maximum throughput the device can deliver in
> best-case signal conditions).
>
>> or is it a combination of these?
>
> Usually it's a combination; especially since the WiFi capacity var= ies
> wildly with signal conditions (as devices move around relative to the<= br> > AP), general link usage (more devices active mean less available
> capacity for each device, exacerbated by airtime unfairness), and
> interference. Also there are things like excessive retries causing HoL=
> blocking.

Man, what an academic answer!=C2=A0 =C2=A0 Makes me think you have a PhD, o= r something!=C2=A0 What *theoretically* can happen is not what I was fishin= g for=C2=A0 =C2=A0:-D


>> I guess that, with openwrt, Cake is operating on the queue that= 9;s
>> feeding the wifi network, as the modem's queue is out of its >> control... so: is this where the bottleneck usually is?
>
> It certainly used to be; but as uplink connection speeds improve, the<= br> > bottleneck moves to the WiFi link.

Yessss, that's why I was asking....


> The extent to which this happens
> depends on where you are in the world; personally I've been bottle= necked
> on the WiFi link ever since I got a fibre upstream (and with 802.11ax<= br> > rates maxing at >1Gbps, maybe that'll change again?).

THIS is what I was after=C2=A0 =C2=A0:)=C2=A0 =C2=A0one data point, cool - = so far, so good...

Cheers,
Michael

_______________________________________________
Make-wifi-fast mailing list
M= ake-wifi-fast@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/make-wif= i-fast
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