Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call

Gyan Mishra <hayabusagsm@gmail.com> Sat, 23 May 2020 20:44 UTC

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In-Reply-To: <331DE9C9-BF8A-483D-B4D5-366D3FBF4C22@tony.li>
From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Sat, 23 May 2020 16:43:49 -0400
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To: tony.li@tony.li
Cc: "Acee Lindem (acee)" <acee@cisco.com>, Huaimo Chen <huaimo.chen@futurewei.com>, "lsr@ietf.org" <lsr@ietf.org>
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Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call
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On Fri, May 22, 2020 at 9:02 PM <tony.li@tony.li> wrote:

>
> Hi Gyan,
>
> I think with clos spine leaf the mesh is much more intensive and
> problematic with ECMP then a circular topology nodal mesh that results in
> duplicate redundant flooding that slows down convergence.  With spine leaf
> it’s like an X horizontal width axis and then depth is spine to leaf
> links.  With spine leaf as you grow sideways and the spine expand the
> redundant ECMP grows and redundant flooding grows exponentially and is much
> worse then circular nodal mesh.
>
>
> One very nice thing about dynamic flooding is that it computes a flooding
> topology at the node level.  If the adjacency between A and B is on the
> flooding topology, then any single link between them may be used for
> flooding.  If you have 128 way parallel links, this is an immediate 128x
> improvement in flooding overhead.  What’s more, A and B do not need to
> agree on which link they are using and can use different links, resulting
> in an asymmetric situation, without any loss of correctness or performance.
>

   Gyan>. Agreed.  The dynamic flooding really helps with X way ECMP
prevalent in high density data center clos multi tier leaf spine parial
mesh topologies that scale massive bandwidth breadth wise horizontally for
E-W flows.

>
> Regards,
> Tony
>
> --

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*Gyan Mishra*

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