[Bloat] less than best effort: TCP - flexis - A New Approach To Incipient Congestion Detection and Control

[Qian Li]

Hello again,

I have uploaded the source code to GitHub. You can find it here:

https://github.com/tinalee77/FlexiS

I have done some editing to the original code that was used to produce the
results in the paper. First, I removed all debugging statements. Second, I
updated comments so that they are more readable. Third, I made variable
names consistent with the paper. And finally, I licensed it with Gnu GPL.

Best regards,
Qian





On Thu, Apr 7, 2022 at 10:35 PM Qian Li <biz.tinalee at gmail.com> wrote:

> Hi Dave,
>
> I was just told that I am allowed to distribute the code freely. I will
> upload it to GitHub and will send you the link as soon as I am done with it.
>
> As for the AQM test, I set the QDisc to FQ-CoDel, CoDel, and CAKE, but
> none worked on CORE. In contrast, RED and PIE worked as expected. As far as
> I know, the major difference between these two groups of AQMs is the time
> when the packets are dropped. But I am not 100% sure it was the cause. I
> may somehow test FlexiS or FlexiR (FlexiS adapted to the receiver side) on
> a testbed with various AQMs. But it will be toward the end of the
> adaptation I guess :)
>
> Best regards,
> Qian
>
> On Thu, Apr 7, 2022 at 8:52 AM Dave Taht <dave.taht at gmail.com> wrote:
>
>> On Tue, Apr 5, 2022 at 8:44 AM Qian Li <biz.tinalee at gmail.com> wrote:
>> >
>> > Dear Dave,
>> >
>> > Thank you for your interest in my work.
>> >
>> > I have read another paper authored by D. Rossi at el. presenting the
>> priority inversion problem of LEDBAT when it is used together with AQM. And
>> it has become one of the factors that motivated me to devise a new LBE CC
>> that can preserve low priority even when AQM is used.
>>
>> We'd given up hope circa 2014 as of the publication of the paper I
>> cited, and moved on.
>>
>> >However, I could not test FlexiS with CoDel on the CORE emulator
>> probably because CoDel drops packets at the dequeue time.
>>
>> I don't really understand that statement.
>>
>> > More tests should be done to verify that FlexiS does preserve low
>> priority in the presence of various AQM algorithms.
>>
>> Yes. until fairly recently I had had a testbed setup that allowed
>> testing of various tcps and aqm systems, but its been in storage since
>> covid.
>>
>> > I am now adapting FlexiS to the receiver side. The main motivation to
>> do so is that there might be HTTP/TCP proxies between the sender and the
>> receiver. A receiver side LBE CC and make the connection between the proxy
>> and the receiver LBE. In this work, I am going to tackle some open issues
>> with FlexiS. For example, I am going to test if trend analysis can be done
>> based on one way delay so that the throughput is less affected by ack path
>> congestion. And I am going to evaluate various techniques to reduce rate
>> below 2 mss per RTT. This may include what you have suggested -- use small
>> packets and sub-packet window. I am also interested in using pacing to slow
>> down sending rate and maybe more alternative solutions.
>>
>> Cool!
>>
>> >
>> > I don't have a git tree for the source code mainly because I don't know
>> if I am allowed to publish the code as open source. If you are interested
>> in the source code, I can ask the University of Oslo if I am allowed to
>> distribute it freely?
>>
>> I would hope they would allow publication. The world is full of half
>> baked projects that if only someones new also stepped in, were
>> completed. An example of this is BBR which originally was about half
>> what it is today, until source was released among the right people.
>>
>> >
>> > Best regards,
>> > Qian
>> >
>> >
>> >
>> > On Sun, Apr 3, 2022 at 6:38 AM Dave Taht <dave.taht at gmail.com> wrote:
>> >>
>> >> Dear Qian:
>> >>
>> >> Pretty promising paper. I liked that it tackled congestion on the ack
>> >> path, among other things.
>> >>
>> >>
>> https://www.techrxiv.org/articles/preprint/TCP_FlexiS_A_New_Approach_To_Incipient_Congestion_Detection_and_Control/19077161/1/files/33905018.pdf
>> >>
>> >> I like also that you tackled, inter-rtt fairness, and, ledbat's
>> >> latecomer advantage problem, and in fig 9, the basic problem with
>> >> delay based LBE vs AQMs (in that ledbat degrades to reno)... [1]
>> >>
>> >> Towards your conclusion...
>> >>
>> >> I have always disagreed with the "don't reduce segment size" crowd,
>> >> btw. If you have a rate where you need to go below 2mss, it doesn't
>> >> hurt the network to reduce the size of the packet, and you can keep
>> >> the signal strength up by reducing that size and continuing to sample
>> >> rtt, to respond quickly.
>> >>
>> >> Even if you are only passing a single byte of data, by lowering this
>> >> below everyone else's 2mss noise floor, you still eventually win, and
>> >> also you occupy space in packet fifos, reducing overall latency, as
>> >> bytes=time. IMHO.
>> >>
>> >> elsewhere, sub-packet windows are being experimented in bbrv2, I'm
>> >> told, but not in LBE.
>> >>
>> >> I'm also a big believer in packet pacing, and I think this is the
>> >> first paper I've seen that attempted LBE with it. Thx!
>> >>
>> >> Got a git tree?
>> >>
>> >> [1] do wish you'd had cited
>> >> https://perso.telecom-paristech.fr/drossi/paper/rossi14comnet-b.pdf
>> >>
>> >> --
>> >> I tried to build a better future, a few times:
>> >> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
>> >>
>> >> Dave Täht CEO, TekLibre, LLC
>>
>>
>>
>> --
>> I tried to build a better future, a few times:
>> https://wayforward.archive.org/?site=https%3A%2F%2Fwww.icei.org
>>
>> Dave Täht CEO, TekLibre, LLC
>>
>
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