No Announce: thanks, we agree

Well, given LSP flooding is unrelible as well it seems no better and no worse 
if we RTX. The PSNP bits will be hanging there and I guess we have to put it on 
a RTX mechanism or we rely on CSNP. Good comment.

Yes, the PSNPs are _in addition_ so yes, I agree also here we can fall back on 
those. I kind of prefer those since it doesn’t change protocol behavior further 
than it already does by sending the additional PSNP

Thanks


  *   Tony

From: Les Ginsberg (ginsberg) <[email protected]>
Date: Friday, 29 July 2022 at 15:08
To: Antoni Przygienda <[email protected]>, [email protected] <[email protected]>
Subject: Comments on draft-white-lsr-distoptflood-03
[External Email. Be cautious of content]


Tony (and everyone) -

Following up on the brief discussion about this draft at today's WG meeting...

I withdraw the comment regarding having to announce use of the algorithm. After 
rereading I agree this is not necessary.

Regarding my second comment about the use of PSNPs as a recovery mechanism in 
cases where topology changes temporarily compromise the optimized 
flooding...the draft says in Section 2.3

<snip>
o  Set a short timer; the default should be one second

   o  When the timer expires, send Partial Sequence Number Packet (PSNP)
      of all LSPs that have not been reflooded during the timer runtime
      to all neighbors unless an up-to-date PSNP or CSNP has been
      already received from the neighbor
<end snip>

Given that PSNPs are unreliable, how can you guarantee that the neighbor has 
received the PSNP(s) required by the most recent set of LSP updates which were 
NOT flooded to that neighbor?

The traditional way of closing this gap is to send periodic CSNPs on interfaces 
where flooding may have been suppressed. In this way you guarantee the 
reliability of the update process.
The recovery time may be a bit slower as sending CSNPs every second is 
excessive - but I do not see how you guarantee reliability without periodic 
transmissions.

Or do you mean to say send the PSNP once IN ADDITION to periodic CSNPs?? This 
would allow quicker recovery in most cases while using a slower periodic timer 
for the CSNPs as protection in case the PSNP was lost.

   Les


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