[c-nsp] Forcing BGP to propagate only after route is in the FIB

[heasley]

Thu, Sep 15, 2016 at 03:08:18PM +0300, Saku Ytti:
> Hey Octavio,
> 
> > We are noticing our ASR 1002 is propagating BGP-learned routes to its
> > neighbors after the path is chosen but before the route gets installed
> > in the FIB.
> >
> > With the increasing size of the BGP table, this is causing race
> > conditions that turn into traffic loops during convergence. The router
> > attracts traffic but returns it back to somebody else because the route
> > is not yet in the FIB or it is outdated in the FIB.
> >
> > Is there a way to force the router to wait until a route is installed
> > all the way in the FIB before having it propagated to the neighbors?
> 
> I don't think so. This is issue which has plagued Juniper RPD for years.
> 
> Technically I believe fix would be to add flag to FIB entries
> signalling HW presence. Then when HW installs it, it should raise
> interrupt or such, to get this flag inserted. But it might be that HW
> does not support this (At any reasonable performance).

increasing the advertisement-interval might improve the probability that
routes are installed before being adverstised...but will increase AS-wide
convergence time.