Re: [Lsr] Flooding across a network

tony.li@tony.li Thu, 07 May 2020 15:52 UTC

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Sender: Tony Li <tony1athome@gmail.com>
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Date: Thu, 7 May 2020 08:52:43 -0700
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To: "Les Ginsberg (ginsberg)" <ginsberg=40cisco.com@dmarc.ietf.org>
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Subject: Re: [Lsr] Flooding across a network
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Les,

 
> I have specifically used an example where “microloop avoidance” is not applicable. So I did not want to use the term “microloop” but rather used “loop” so as not to suggest that “microloop avoidance” is a potential solution for the sub-optimal behavior.
> Hope you can appreciate that point.
>  
> It would be easy enough to include more nodes in the topology which only support slow flooding. The end result would be the same.
> I have kept the example simple in the hopes we could more easily agree that what I describe can happen when not all nodes support faster flooding – which is the only point I am trying to make. Whether the ratio of Fast/Slow nodes is large or small or about the same doesn’t eliminate the possibility that the same behavior could be seen – though it might alter the location of the topology change which would be problematic.
>  
> From an operator’s POV, I am pretty sure that what you really care about is whether packets get successfully forwarded or not. I am demonstrating that it isn’t safe to assume forwarding behavior will be optimal when not all nodes support fast flooding.


Your point is well-made. There are certainly going to be topologies where making flooding faster would result in worse behavior.

However, the point is that there are also topologies where flooding faster would improve convergence. To support those, we must have faster flooding. Please focus on that goal.

Regards,
Tony