Subject: Re: Summarization but still unnecessary new LSAs

From: "Jeyanath Minto J - CTD, Chennai." <[email-masked]>
Date: Wed, 16 Jul 2003 13:29:25 +0530

hi Juergen ,
        u only  originate summary LSA , when there is real a change , its
including the cost. otherwise no need to originate Summary LSA. Moreover, a
unchanged LSA (may be a new instance  )into a area , never tirgger the SPF.
see section 16.5 of the RFC 2328.

Cheers
Minto Mascarenhas
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-----Original Message-----
From: Juergen Arlt [mailto:[email-masked]]
Sent: Wednesday, July 16, 2003 12:57 PM
To: [email-masked]
Subject: Summarization but still unnecessary new LSAs

In a very basic config a router is ABR with one interface in Area 0.0.0.0
and two interfaces in area 0.0.0.1. For those two interfaces I manually
configured a summary to get only one LSA Type 3 into the backbone area. (the
interfaces are 192.168.1.1/24 and 192.168.2.1/24 with a summarization of
192.168.0.0/16).
Now I found that whenever there is a change on those two interfaces (one
going down or up) a new summary LSA is generated into the backbone area. It
does not contain new information, only the sequence number is incremented.
In the worst case (like link flapping) the router would create new LSAs
permanently that would be flooded into the backbone area. Although no SPF
would be started the number of LSAs to process would force unnecessary CPU
load on the backbone devices.
I did not find an RFC stating how this summarization should be implemented
but the way I found this router working is probably not the best.
Can someone point me to a document if there is one?
Regards
Juergen

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From: "Jeyanath Minto J - CTD, Chennai." <[email-masked]>
Date: Wed, 16 Jul 2003 14:45:19 +0530

hi Juergen ,
  ignore my last mail. Sorry to group.

Cheers
Minto Mascarenhas

-----Original Message-----
From: Jeyanath Minto J - CTD, Chennai.
[mailto:[email-masked]]
Sent: Wednesday, July 16, 2003 1:29 PM
To: [email-masked]
Subject: Re: Summarization but still unnecessary new LSAs

hi Juergen ,

Cheers
Minto Mascarenhas

---

From: "Pat Murphy - (650)329-4044" <[email-masked]>
Date: Wed, 16 Jul 2003 10:07:32 -0700

Juergen,

>RFC 2328, Section 12.4.3 states

  At most a single Type 3 summary-LSA is originated for each
  range.

The implication of this statement is clear. If the local router
has already originated a summary-LSA for a range, subsequent
re-originations caused by other networks subsumed by the range
should be skipped. As long as the set of networks subsumed by a
range is non-empty, the summary-LSA should undergo normal
aging. It would have been nice if this had been stated more
explicity, but "it is common sense".

Pat