Subject: Re: [OSPF] Request for a slot for LSA Correlation discussion

From: Anton Smirnov <[email-masked]>
Date: Sat, 01 Nov 2008 14:15:52 +0100

Hi Mukul,
   I don't plan attending Minneapolis meeting so I went through the
paper now.
   Academic papers investigating possibility of considering reduced set
of nodes during recalculation in link state routing protocols were done
I believe in 80-th years of the last century. And identifying scope of
changes and need to do recalculation is obviously integral part of each
such algorithm.
   Furthermore, those algorithms typically consider not only the fact
that vertex (i.e. 'node' in your paper) or edge ('link') went down but
also if that element was actually computed as part of shortest path tree
during last recalculation. Idea is that if 'link' was not used last time
then tree wouldn't change if that link went down, so no need to do any
recalculation.
   Sorry to sound unenthusiastic but it seems to me your work is not
only 20 years late but it is also covering just portion of those works.
The only novelty is that it is being packed as Informational RFC...

   Thanks,

Anton

Mukul Goyal wrote:
> Hi Acee/Abhay
> 
> I recently posted a ID on LSA correlation:
> 
> http://www.cs.uwm.edu/~mukul/draft-goyal-ospf-lsacorr-00.txt
> 
> I was wondering if I can get a presentation slot at the Minneapolis meeting?
> 
> Thanks
> Mukul
> 
> _______________________________________________
> OSPF mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/ospf
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---

From: Mukul Goyal <[email-masked]>
Date: Mon, 3 Nov 2008 07:00:03 -0600 (CST)

Hi Anton

Thanks for your comments. The LSA correlation is not an incremental SPF algorithm. It simply means - correlate the LSAs to identify the topology change and use this event (the topology change identification) as the trigger to the state machine that determines when a routing table calculation will be done. At present, OSPF uses a new LSA as this trigger.

>From your message I got the impression that some of the incremental SPF algorithms published in 1980s had LSA correlation like approach as an integral part. I would really appreciate some pointers. In my literature search, I was not able to find any previous use of an LSA Correlation like approach.

Regards
Mukul
 
----- Original Message -----
From: "Anton Smirnov" <[email-masked]>
To: "Mukul Goyal" <[email-masked]>
Cc: [email-masked]
Sent: Saturday, November 1, 2008 8:15:52 AM GMT -06:00 US/Canada Central
Subject: Re: [OSPF] Request for a slot for LSA Correlation discussion

   Hi Mukul,

   Thanks,

Anton

---

From: Anton Smirnov <[email-masked]>
Date: Mon, 03 Nov 2008 23:20:43 +0100

Hi Mukul,
   as I wrote, SPF on subset of LSAs must somehow determine subset of
LSAs affected by a change. This by definition requires analysis of
change in the LSA, i.e. comparing 'old' and 'new' LSAs. In this sense
"LSA correlation" is integral part of incremental SPF.

   I don't have pointers ready but try searching for papers by McQuillan
& Rosen.
   Thanks,

Anton