[c-nsp] BGP Fast-external-fallover

[Stephen J. Wilcox]

On Sun, 13 Mar 2005, David Barak wrote:

> 
> --- Daniel Roesen <dr at cluenet.de> wrote:
> > On Sat, Mar 12, 2005 at 09:43:59PM -0800, David
> > Barak wrote:
> > > Wait, your provider is dampening you, their
> > customer? 
> > > Something's not right here - generally dampening
> > is
> > > used toward peers, not customers, because
> > dampening is
> > > the converse of the SLA approach.  Personally, I
> > > wouldn't pay for service from a provider which
> > would
> > > willfully permit me to remain down...
> > 
> > Actually, your provider does a service to you. When you fixed your flapping
> > for good, you can call your provider and have him reset the damping
> > holddown.
> 
> So the burden goes from the provider to the customer?  As Randy Bush used to
> say, I encourage my competitors to do this.

if you're flapping you will get dampened somewhere, better your upstream does it 
than the rest of the internet imho. and assuming you are redundant and your 
other upstream isnt affected this will ensure traffic is flowing over the most 
stable path.

Steve

> 
> > If he would pass this flapping
> > on, all/most/many
> > peers/upstreams of him would have your prefix
> > dampened, and almost
> > nothing he can do about it. You stay down until all
> > their reuse
> > timers expire.
> > 
> 
> But if you postulate an enterprise with N locations,
> the other N-1 locations will find the location with
> the flapping circuit completely unreachable, rather
> than only partially unreachable.  
> 
> > Propagating the instability hurts more than damping
> > it early at the
> > source.
> 
> Dampening, like bogon filtering, is something which is
> a good idea in theory, but in practice, can do far
> more harm than good, unless it's very, very carefully
> managed.  
> 
> 
> David Barak
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> 
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