Re: [Lsr] New Version Notification for draft-white-lsr-distoptflood-00.txt

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> I agree with Les. While you might get some flooding reduction out of
> this, it wouldn’t be hard to better with a flooding next-neighbor
> algorithm that was more well-thought (e.g., RFC 5614). Here are my
> concerns:

We are trying to avoid the LLS work in OSPF ... 

In testing, this shows a dramatic decrease in the amount of flooding in 3 and 5 stage fabrics. Of course, this would also work for any random topology (even MANET networks), so it's not really limited to DC fabric use.

> 1.	It seems that while it is a distributed algorithm, the change of
> flooding scope makes it somewhat quasi-centralized as you are making the
> flooding decision for your neighbor. Perhaps, these parts of the
> algorithm were developed with different Email addresses 😉

I switched off gmail ... which is probably a good thing. 😊

> 2.	I don’t like the fact that IS-IS routers are changing the
> flooding scope of an LSP that they didn’t originate themselves (Les’s
> concern). This flooding scope modification could be removed but then
> that would take away the novelty of the algorithm.

This, it seems to me, is always going to be true of any flooding optimization -- unless you have the originator "mark" where each LSP "should go," something like a BIER bitfield embedded in the packet. This is true, btw, of the centralized flood reduction mechanisms I've seen, and is even true of 5614.

> 3.	The mechanisms for recovering from flooding failures is pretty
> brute force…. A CNSP with every neighbor at sub-second intervals? Seems
> this could negate much of what you are saving in flooding.

It's not constant subsecond CSNPs, but rather a single additional CSNP. 

> 4.	The way the document is written, the flooding decision is made
> independently for every LSP. This seems unnecessary and it be per
> neighbor (or even less granular) with no loss of optimization.

I don't think it's implemented this way ... perhaps Shraddha can comment on how she implemented it. The FR/R implementation is not per LSP, either, AFAIK, but I can poke at the code again.

😊 /r