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

Sun Aug 21 14:27:43 EDT 2022

I have not had time to play with this much more, but it remains
promising. Although you dismiss the ieas of not reducing the mss as
not cost effective, I think for certain kinds of traffic it it worth
pursuing.

Also, based on some tests on a busy wifi network elsewhere, doing
packet pacing on a per packet (rather than two packets at a time)
seems interesting.

What are you working on these days?

On Fri, Apr 8, 2022 at 11:56 PM Qian Li <biz.tinalee at gmail.com> wrote:
>
> 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

-- 
FQ World Domination pending: https://blog.cerowrt.org/post/state_of_fq_codel/
Dave Täht CEO, TekLibre, LLC