Re: [Lsr] Congestion (flow) control thoughts.

"Gengxuesong (Geng Xuesong)" <gengxuesong@huawei.com> Thu, 07 May 2020 10:28 UTC

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From: "Gengxuesong (Geng Xuesong)" <gengxuesong@huawei.com>
To: "tony.li@tony.li" <tony.li@tony.li>
CC: "lsr@ietf.org" <lsr@ietf.org>, Christian Hopps <chopps@chopps.org>
Thread-Topic: [Lsr] Congestion (flow) control thoughts.
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Date: Thu, 7 May 2020 10:28:41 +0000
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Subject: Re: [Lsr] Congestion (flow) control thoughts.
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Hi Tony,

I agree that "minimal flooding time " is a good choice, which may differ from the traditional cc in layer 4, which is difficult to get the completion time for each flow.
I am still a little confused about " fast brand X needs to not overrun slow brand Y while performing well with fast brand Z". Is this talking about interoperation between different company device, which may use different type of cc mechanism?

Best Regards
Xuesong 

> -----Original Message-----
> From: Lsr [mailto:lsr-bounces@ietf.org] On Behalf Of tony.li@tony.li
> Sent: Thursday, May 7, 2020 12:02 AM
> To: Gengxuesong (Geng Xuesong) <gengxuesong@huawei.com>
> Cc: lsr@ietf.org; Christian Hopps <chopps@chopps.org>
> Subject: Re: [Lsr] Congestion (flow) control thoughts.
> 
> 
> Hi Xuesong,
> 
> > <Xuesong> I think there is no need to distinguish the concept of flow control
> and congestion control, considering that the core idea is the same: monitor the
> sending rate to match the capability of the bottleneck, no matter there are
> competitors or not. And the control loop is necessary in both case.
> 
> 
> This matches my perspective.
> 
> 
> > <Xuesong> Thank you for explaining about the bottleneck of flooding and
> different cc solutions that are under discussion. It is helpful and I will read the
> drafts.
> > There is still one more question left in the previous email: " What is the
> criteria of comparing different solutions?". I think this is crucial for further
> discussion and comparative tests. I notice that in Bruno's data, some
> parameters are mentioned, such as " Duration"," LSP/second"," avg inter-LSP
> delay", "retransmission time". I'm wondering whether it is able to choose a
> better solution through these parameters. If not, what should be added or
> considered. (Some other issues are also considered when choosing cc
> mechanism in layer 4, such as: fairness among flows, co-existence with other
> cc mechanism .. )
> 
> 
> Sorry for missing the question. The criteria are, I think, quite clear: minimize
> overall flooding time.  As Bruno’s figures show, that does NOT happen simply
> by transmitting at the maximum rate. That causes overruns, resulting in
> retransmissions and that ends up being quite slow (tho we can work on that
> too). The question then is: what control mechanisms do we put in place to
> ensure minimal flooding time? This needs to interoperate across the full
> spectrum of implementations: fast brand X needs to not overrun slow brand Y
> while performing well with fast brand Z.
> 
> The floor is very much open.
> 
> Tony
> 
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