Robert –

Let’s please not introduce issues which are not relevant. ☺

Any flooding optimization solution only applies to a single LSDB – and the set 
of nodes/links which support flooding of that LSDB. This means (in IS-IS speak):

·         Level-1 is distinct from Level-2. I could choose to apply flooding 
optimizations to one level and not the other if I wished. Or use a different 

·         One MI instance is distinct from another

·         MT is not relevant since all the MT specific advertisements for all 
supported topologies are contained within a single LSDB (I.e., we do not 
support MT specific flooding)



From: Lsr <> On Behalf Of Robert Raszuk
Sent: Sunday, February 03, 2019 12:37 PM
To: Tony Li <>
Cc: Huaimo Chen <>;; David Allan I 
Subject: Re: [Lsr] Moving Forward [Re: Flooding Reduction Draft Redux]

I fully agree and support proceeding with  draft-li-dyanmic-flooding and to 
include protocol extensions in it for centralized topology propagation as well 
as basic hooks like "execute dynamic protocol number X" for distributed 

However one may observe that separate distributed algorithms may define their 
own protocol extensions and they should not break the above in any way.

Then there is already some requirements of building two disjoined topologies in 
any rich ECMP DC fabric one say for primary paths the other for backup flows. 
(Case of active-active dual streaming applications). Question arises if this 
would be addressed also as part of basic spec, be combined with one or many of 
distributed algorithms or will require yet one more document which in turn will 
"extend" all of the above ? And before anyone suggests multi instance approach 
with logical or physical link separation it is not the right direction here. If 
anything perhaps MTR or SR come a bit closer.

Kind regards,

On Sun, Feb 3, 2019 at 9:14 PM <<>> wrote:

I think that this discussion would be greatly clarified if we clearly separated 
the discussion between

a) the algorithm for computing the flooding topology, and
b) the signaling to indicate how to proceed.

I think that we are all in agreement that the algorithms can and should be 
separated from the signaling.

I think that we are all in agreement that each algorithm should be independent.

I’m of the opinion that the centralized signaling is a bit more extensive than 
the signaling for the distributed mode, but that there is also considerable 
overlap and that things would
be unnecessarily redundant if we were to separate them. I believe that we are 
not in disagreement about the basics for the distributed signaling.

If you disagree with this, please clearly articulate why you feel the signaling 
should be separated.

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