OSPF performance/SPF calculations

Ondrej Zajicek santiago at crfreenet.org
Fri Apr 23 14:09:50 CEST 2010


On Fri, Apr 23, 2010 at 12:38:59PM +0200, Joakim Tjernlund wrote:
> > > But this won't fix multiple ptp I/Fs between the same two routes and
> > > I don't think it will work if one end is unnumbered and the other one is not.
> >
> > Our algorithm (in the git tree) works well for multiple ptp ifaces between
> > the same two routers (because both the SPF and the calc_next_hop() chooses
> > the same (cheapest) ptp link.

> Even if all local PtoP I/Fs have the same IP address or no IP address?

Yes, for the version in the git tree.

Or more precisely, it works for links having the same ptp address.
(a link with ptp/peer addresses is considered unnumbered).

If there is really no IP address on the link, it will not work, but
for several completely different reasons - BIRD core would not accept
such route.

> What does this comment in calc_next_hop mean?
>  /*
>      * Remaining cases - local neighbours.
>      * There are two problems with this code:
>      * 1) we use IP address from HELLO packet
>      *    and not the one from LSA (router or link).
>      *    This may break NBMA networks
>      * 2) we use find_neigh_noifa() and does not
>      *    take into account associated iface.
>      *    This breaks neighbors connected by more links.
>      */

This is an old code, which has some bugs i fixed a two weeks ago:

The current version is here:

http://git.nic.cz/bird/browser/proto/ospf/rt.c

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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