Re: ospf limits...

[Rohit Gupta <[e-mail]>]

A draft by Amir Hermelin
(draft-ietf-isis-ext-lsp-frags-02.txt) now changes
that and we can have LSP fragments > 256

Rohit

--- klara moser <[e-mail]> wrote:
> I think that the limit for the ISIS topologies comes
> from the fact that
> there could be only 256 LSPs generated and this is
> for all route types.
> It is still very big database (256 x 1470bytes)...
>
> Klara
>
> Rohit Gupta wrote:
>
> > I remember reading somewhere that ISIS can support
> > bigger areas than OSPF though i am not sure as to
> how
> > exactly, given that both are link state and almost
> > similar.
> >
> > So if you cant scale well with OSPF then you can
> > consider ISIS also.
> >
> > ----- Original Message -----
> > From: "klara moser" <[e-mail]>
> > To: <[e-mail]>
> > Sent: Thursday, March 06, 2003 11:41 PM
> > Subject: Re: ospf limits...
> >
> > > Hi Ravi,
> > >
> > > As far as I know the OSPF protocol has only one
> > limitation on the topologies
> > > size - the Network and Router LSA size. The max
> is
> > 64KB. This limits the number
> > > of links the router can have in a single area,
> > because it has to advertise them
> > > in a single Router LSA. You can do the math. It
> is
> > something like 5 000 links.
> > >
> > > Klara
> > >
> > > Quaizar Vohra wrote:
> > >
> > > > I think the main factor is the amount of
> flooding
> > a router has to do
> > > > which depends on how many adjacencies you have
> and
> > how many LSAs you
> > > > have to flood to each adjacency. So it is
> useful
> > to divide your
> > > > network into multiple areas so as to reduce
> > flooding. Also large
> > > > no. of adjacencies in a single area can result
> in
> > rather large router
> > > > LSAs which causes a lots of fragmentation and
> adds
> > to the flooding
> > > > load.
> > > >
> > > > Quaizar
> > > >
> > > >  > I am in the midst of redesigning an OSPF
> > network to accommodate
> > > >  > significant growth, especially in the Area
> 0
> > backbone. There has been
> > > >  > some concern about the size of the OSPF
> > topology that would result and
> > > >  > whether the routing protocol would remain
> > robust, able to handle the odd
> > > >  > flapping link or memory leak. The network
> in
> > question is using high-end
> > > >  > routers with high speed links (at least
> DS-3).
> > > >  >
> > > >  > Are there any heuristics that someone has
> which
> > may give us an idea of
> > > >  > the comfort zone in terms of the database
> size,
> > number of neighbors,
> > > >  > routers, etc?
> > > >  >
> > > >  > Or, could someone share information on the
> size
> > of large OSPF
> > > >  > implementations that they are aware of?
> > > >  >
> > > >  > I know that this issue is rather vague
> (clouded
> > in too many unknowns)
> > > >  > and may only result in rather ambiguous
> > > >  > answers, but, one never knows.
> > > >  >
> > > >  > Thanks,
> >
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