Hi Tony,

Thanks for jumping in and the explanation. I support the idea of tradeoffs 
between pefection and simplicity. Analysis about the change of topology can be 
tricky, especially when adding links, and for a distributed algorithm it’s more 
important to achieve a definitive result. Maybe it’s easier to optimize some 
cases in a centralized-mode, but we always need to consider benefit-cost ratio.

The text in the draft is “MUST be”, so I thought I’d ask to confirm.

Thanks,
Yingzhen

From: Tony Li <[email protected]> on behalf of "[email protected]" 
<[email protected]>
Date: Friday, June 5, 2020 at 2:56 PM
To: Yingzhen Qu <[email protected]>
Cc: "Acee Lindem (acee)" <[email protected]>, "[email protected]" 
<[email protected]>, Huaimo Chen <[email protected]>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - 
draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call


Hi,



I have a question regarding the draft. At the end of section 3, it says if 
there is any change in the base topology, the flooding topology MUST be 
re-computed. So in case of a link failure in the base topo, it’s possible that 
the link is not part of the flooding topology (e.g. one of the multiple links 
between two nodes), it might be optimal if we can figure it out and save 
recalculation here.


This comment isn’t specific to this algorithm, so you’ll pardon me if I jump in.

Always recomputing the flooding topology is always a safe thing to do and for 
the case of a distributed algorithm is probably the safest design choice.

Doing the analysis about the change is not exactly trivial and computing the 
flooding topology is not that hard.  We are typically not short of CPU cycles 
and recomputing the flooding topology is outside of the critical convergence 
window, so while there is some theoretical benefit, it’s not at all clear that 
it’s of great practical benefit.  But it is up to those specifying the 
algorithm.

Regards,
Tony



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