Routing flaps, was Re: Ping flooding

Fri Jul 12 16:34:58 UTC 1996

Forgot to throw one more item in here...

On Fri, 12 Jul 1996, Paul Ferguson wrote:

> I'm sorry, but I'm afraid that you're missing the point here.
> 
> In most larger ISP backbones, the behavior of their IGP is indeed
> visible to the public, since in most instances, most of the Internet
> traffic relies on the stability of these interior (an esoteric term)
> networks. Therefore, whether interior or exterior flap is really of
> no relevance in this context.
> 
> In smaller ISPs, where not a great deal of public traffic is transiting
> their (interior) backbone, granted, it is of lesser importance and
> visibility.

What I forgot to say is that I fully agree with what you are saying here- 
I doubt that a large provider such as Sprint or MCI or Agis or any other 
major internet backbone is going to be able to hide much of their 
internal route flapping, as their internal routes ARE their external routes.

My original note was intended to reply to the specific case of using 
dynamic routing to distribute routes which could just as easily be done 
with static routes - I.E. where there is one and only one path to the 
destination.  In this case, it is sometimes desirable and necessary to 
run some sort of interior routing protocol, but it is not desirable that 
flaps caused by a break along the one and only one path be propogated to 
the outside world, but instead the packets should be null0'd at the point 
of path convergence.

-forrestc at imach.com