Re: [Lsr] Open issues with Dynamic Flooding

tony.li@tony.li Tue, 05 March 2019 16:17 UTC

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Date: Tue, 05 Mar 2019 08:16:57 -0800
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To: Peter Psenak <ppsenak@cisco.com>
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Subject: Re: [Lsr] Open issues with Dynamic Flooding
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Peter,

>>    (a) Temporarily add all of the links that would appear to remedy the partition. This has the advantage that it is very likely to heal the partition and will do so in the minimal amount of convergence time.
> 
> I prefer (a) because of the faster convergence.
> Adding all links on a single node to the flooding topology is not going to cause issues to flooding IMHO.


Could you (or John) please explain your rationale behind that? It seems counter-intuitive.



> given that the flooding on the LAN in both OSPF and ISIS is done as multicast, there is currently no way to enable flooding, either permanent or temporary, towards a subset of the neighbors on the LAN. So if the flooding is enabled on a LAN it is done towards all routers connected to the it.


Agreed.


> Given that all links between routers are p2p these days, I would vote for simplicity and make the LAN always part of the FT.


I’m not on board with this yet.  Our simulations suggest that this is not necessarily optimal.  There are lots of topologies (e.g., parallel LANs) where this blanket approach is suboptimal.

Tony