From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) (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 393E83CB35 for ; Thu, 28 Jul 2022 05:26:49 -0400 (EDT) Received: by mail-pl1-x632.google.com with SMTP id b22so1296676plz.9 for ; Thu, 28 Jul 2022 02:26:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=domos-no.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=5uMFQqSWm0xe/Qdu335bXkVrYPN7DKuolXRJvCqAURs=; b=FOEkg1jwQHBB3jWYPRhoYtugt0NTVzJE4TjkHHl9tzGNvvpfP14hxNALbtB73/+NJ6 4e1W+AwF4yAnnAjreQZqOIyxZpKcXbLAcHkV7PKWaHQgRp5gsbXpKyotYx11u/JHngJz xmYsZSApNYpKQ/QkMtbpNSqTQksdguUQc1dal53gOH7vojnHt4kcoeddNSj8m5dC4LrL Jn+E5srrjNwSrMqEiEtiVE7328OXrKO6kBX6VehhiDZYm5IU2MXKkJAtxFrmtnz8aSQc k93PpDA7BjYUQAkd2OaXJz9nFgGmuhGvbsN8PVul6sh7lyW5ZF0mK5FyHadKCoqEJZPu rQWg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=5uMFQqSWm0xe/Qdu335bXkVrYPN7DKuolXRJvCqAURs=; b=MeWH3Y+CEbVOcUAltwtjLVCsz2Kj7RsBTkbeJvxxJnurml2/TRG3kJXsJawPRzaeVx OUS+hlWk6ktsOG8ZbvFwuYArXBDbdW0kWyvLgkkjPM+8/Yu/Rvqg0neLgUQjX1ZmdClt Eb5FdgTnk/ZGR18QNeB08LCdE3WC4EQvj5BdYOS9Nvsj2AKlmze9dnr7MchEeJjLejbL PJuYj8Q4Rbb57ksFoIsEJsKgdmqC1ADe7XHx9b6vtjSEIEhk4pJDwEQFLwXWT0oBs8W8 SahcqxVCa7G429DZOXV777SFBmTQ3JiCQdNqIqk+WRR41WnAwmBG60KfbZ5SrnJy/T3U N2Og== X-Gm-Message-State: AJIora+3SxqGXbPCzoDVxMySFmGbR6q3Pm5siwEn4+Fa57fJ9oIZOd0y 3yJfCSGSZq3aaF0PcwUIC8YhRoTNBL2dFBQe2q2iIg== X-Google-Smtp-Source: AGRyM1uUI9EJntUK3Uy+nQi+fhWPfzTa1ZfvD+0MY4dx88SToGnk7ge3Vkr3SXhUpFM0N1fFPq7bPgERk8JLsxMDPbE= X-Received: by 2002:a17:90a:8c88:b0:1f2:12b0:ae9e with SMTP id b8-20020a17090a8c8800b001f212b0ae9emr9485058pjo.42.1659000408123; Thu, 28 Jul 2022 02:26:48 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: =?UTF-8?Q?Bj=C3=B8rn_Ivar_Teigen?= Date: Thu, 28 Jul 2022 11:26:36 +0200 Message-ID: To: "Bless, Roland (TM)" Cc: Dave Taht , starlink@lists.bufferbloat.net, codel@lists.bufferbloat.net Content-Type: multipart/alternative; boundary="000000000000023ec605e4da22b2" Subject: Re: [Starlink] Finite-Buffer M/G/1 Queues with Time and Space Priorities X-BeenThere: starlink@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Starlink has bufferbloat. Bad." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 28 Jul 2022 09:26:49 -0000 --000000000000023ec605e4da22b2 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi everyone, Interesting paper Dave, I've got a few thoughts: I like the split into delay-sensitive and loss-sensitive data. Different applications can have different needs and this split allows a queuing algorithm to take those differences into account. Not the first time I've seen this kind of split, but the other one I've seen used M/M/1/k queues (document here: https://www.researchgate.net/publication/2452029_A_Queueing_Theory_Model_th= at_Enables_Control_of_Loss_and_Delay_of_Traffic_at_a_Network_Switch ) That said, the performance metrics are derived from the embedded Markov chain of the queuing system. This means the metrics are averages over *all of time*, and thus there can be shorter periods (seconds, minutes, hours) of much worse than average performance. Therefore the conclusions of the paper should be taken with a grain of salt in my opinion. On Thu, 28 Jul 2022 at 10:45, Bless, Roland (TM) via Starlink < starlink@lists.bufferbloat.net> wrote: > Hi Dave, > > IMHO the problem w.r.t the applicability of most models from > queueing theory is that they only work for load < 1, whereas > we are using the network with load values ~1 (i.e., around one) due to > congestion control feedback loops that drive the bottleneck link > to saturation (unless you consider application limited traffic sources). > To be fair there are queuing theory models that include packet loss (which is the case for the paper Dave is asking about here), and these can work perfectly well for load > 1. Agree about the CC feedback loops affecting the results though. Even if the distributions are general in the paper, they still assume samples are IID which is not true for real networks. Feedback loops make real traffic self-correlated, which makes the short periods of worse than average performance worse and more frequent than IID models might suggest. Regards, Bj=C3=B8rn Ivar > > Regards, > Roland > > On 27.07.22 at 17:34 Dave Taht via Starlink wrote: > > Occasionally I pass along a recent paper that I don't understand in > > the hope that someone can enlighten me. > > This is one of those occasions, where I am trying to leverage what I > > understand of existing FQ-codel behaviors against real traffic. > > > > https://www.hindawi.com/journals/mpe/2022/4539940/ > > > > Compared to the previous study on finite-buffer M/M/1 priority queues > > with time and space priority, where service times are identical and > > exponentially distributed for both types of traffic, in our model we > > assume that service times are different and are generally distributed > > for different types of traffic. As a result, our model is more > > suitable for the performance analysis of communication systems > > accommodating multiple types of traffic with different service-time > > distributions. For the proposed queueing model, we derive the > > queue-length distributions, loss probabilities, and mean waiting times > > of both types of traffic, as well as the push-out probability of > > delay-sensitive traffic. > _______________________________________________ > Starlink mailing list > Starlink@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/starlink > --=20 Bj=C3=B8rn Ivar Teigen Head of Research +47 47335952 | bjorn@domos.no | www.domos.no --000000000000023ec605e4da22b2 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Hi everyone,

Interesting paper Dave, I've got a few thoughts:

=
I like the split into delay-sensitive and loss-sensitive data. D= ifferent applications can have different needs and this split allows a queu= ing algorithm to take those differences into account. Not the first time I&= #39;ve seen this kind of split, but the other one I've seen used M/M/1/= k queues (document here: https://www.researchgate.net/publication/2452= 029_A_Queueing_Theory_Model_that_Enables_Control_of_Loss_and_Delay_of_Traff= ic_at_a_Network_Switch)=C2=A0

That said, the p= erformance metrics are derived from the embedded Markov chain of=20 the queuing system. This means the metrics are averages over *all of=20 time*, and thus there can be shorter periods (seconds, minutes, hours)=20 of much worse than average performance. Therefore the conclusions of the paper should be taken with a grain of salt in my opinion.

O= n Thu, 28 Jul 2022 at 10:45, Bless, Roland (TM) via Starlink <starlink@lists.bufferbloat.net&= gt; wrote:
Hi Da= ve,

IMHO the problem w.r.t the applicability of most models from
queueing theory is that they only work for load < 1, whereas
we are using the network with load values ~1 (i.e., around one) due to
congestion control feedback loops that drive the bottleneck link
to saturation (unless you consider application limited traffic sources).

To be fair there are queuing theory model= s that include packet loss (which is the case for the paper Dave is asking = about here), and these can work perfectly well for load > 1. Agree about= the CC feedback loops affecting the results though. Even if the distributi= ons are general in the paper, they still assume samples are IID which is no= t true for real networks. Feedback loops make real traffic self-correlated,= which makes the short periods of worse than average performance worse and = more frequent than IID models might suggest.

R= egards,
Bj=C3=B8rn Ivar
=C2=A0

Regards,
=C2=A0 Roland

On 27.07.22 at 17:34 Dave Taht via Starlink wrote:
> Occasionally I pass along a recent paper that I don't understand i= n
> the hope that someone can enlighten me.
> This is one of those occasions, where I am trying to leverage what I > understand of existing FQ-codel behaviors against real traffic.
>
> https://www.hindawi.com/journals/mpe/2022/453= 9940/
>
> Compared to the previous study on finite-buffer M/M/1 priority queues<= br> > with time and space priority, where service times are identical and > exponentially distributed for both types of traffic, in our model we > assume that service times are different and are generally distributed<= br> > for different types of traffic. As a result, our model is more
> suitable for the performance analysis of communication systems
> accommodating multiple types of traffic with different service-time > distributions. For the proposed queueing model, we derive the
> queue-length distributions, loss probabilities, and mean waiting times=
> of both types of traffic, as well as the push-out probability of
> delay-sensitive traffic.
_______________________________________________
Starlink mailing list
Starlin= k@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/starlink


--
Bj=C3=B8rn Ivar Teigen=
Head of Research
+47 47335952 | = bjorn@domos.no=C2=A0|=C2=A0www.domos.no
--000000000000023ec605e4da22b2--