Re: LSDB Overflow Limitation?

[Charles Liang <[e-mail]>]

Mitchell,

It sounds like we prefer to pre-allocate the resource,
rather than process the overflow conditions?!
I also belive that the number has to be matched with
the limit counts, and pre-allocating the resource
should be a pratical solution.

What I concerned is the exception? from RFC1765.
If we have to implement this feature, we'd like
to make sure the implementation works for all
the possible cases.  Otherwise, shouldn't we prefer
to announce that my OSPF router will NEVER fall
into LSDB overflow state.

Therefore, I'm wondering that
(1) Is my realization about RFC1765 correct?
(2) Will the problem that I described happen?
(3) Is there any side effect if I use a reserved
and unused field in HELLO-Option?
(4) Is it worth of implemeting RFC1765?

Charles

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Charles,

The number really has to do with
the number of non default AS-external
LSAs.

These are believed to represent the
maj of LSAs in the LSDB.

In my experience, this only occurs
with memory limited routers and
routers within the same area are
normally set to the same values.

Realize that in memory limited routers,
you are pre-allocating enough memory
to cover the limit and that memory will
not be available for other functions.

Mitchell Erblich
-----------------

> Charles Yi-tung Liang wrote:
>
> Hi,
>
> Here below is my understanding from RFC1765
> to process lsdb overflow condition.
>
> Goal: Make every OSPF router to be awared of
> the overflow state, and thus reduce the number
> of lsdb.  That's why we required all the OSPF
> routers setup the same limited lsdb threshold.
>
> Process: As mentioned in RFC1765.
>
> Limitation?/Problem?:
> Since the new LSA update from someone triggers
> overflow state (when currentLSACount == limitedLSACount)
> via flooding, there is chance that certain OSPF router
> will miss such a critial event.  Moreover, the following
> premature actions may make someone else believing
> there is not yet an overflow event.  Why don't we just set
> up a beacon bit to notify everyone?  For example,
> using a reserved filed in HELLO-Option to notify
> overflow.  Afterward, when all the neighbors acked
> with overflow beacon-bit, reset (clear) such a bit.
>
> Could anyone help clearing my doubt?
>
> BTW, if the overflow process needs to be applied
> to Inter-AS LSAs (Area-Oriented), what kind of
> LSA is suggested to be prematured?  Can I leave
> RTRLink, NetLink, and ASSummary alone?
> Will OSPF WG include the overflow process as
> a part of OSPFv3?
>
> Thanks in advance.
>
> Charles