Re: [Idr] draft-spaghetti-idr-bgp-sendholdtimer - Feedback requested

[Robert Raszuk <[e-mail]>]

Hi Jeff,

> So what we are discussing is breaking data plane just because control
> plane
> > has experienced 15 min (or worse recommended 4 min) inability to send
> > keepalives.
>
> A good analogy is the negative impacts of stale routes when you use
> Graceful
> Restart for BGP.  Can you live with the routes in that flavor of stale for
> that long?
>

Unfortunately the answer is "it depends". If my stale route is single
default to the world with working data plane I think the answer is clearly
YES.

So that IMHO sort of raises the question if this should be the default
behaviour.

Then honestly I am not quite clear how it should be handled on sessions
which are setup with draft-ietf-idr-long-lived-gr-00

> * Should we perhaps test data plane before declaring peer's failure and
> > before we reset the session ? (I understand that the paramount motivation
> > is BGP consistency here though - but this is one of those cases where one
> > size may not fit all).
>
> In many of these scenarios, BFD or ping would show the interface up.  It's
> the TCP session that is stalled out.
>

True.

I was rather thinking about checking data plane not to the subject peer but
beyond it (through it). For iBGP - testing next hops. For eBGP some known
test servers in yr network or in the Internet.



> > * Should we first withdraw received routes from our peers before
> resetting
> > the session ? At least data plane will have a chance to converge to a
> > different set of links with no sudden packet drops.
>
> Would you describe the drain scenario with the involved parties and what
> the
> congestion state is as part of that?  I don't think I'm understanding the
> above point.



If I know I will bring BGP sessions down to you (in any case not only with
this draft) I should withdraw paths from all of my peers received over such
session and previously advertised (as best or as add-paths) before
resetting it. So the control plane clears before we touch the data plane.
Just to make the end to end reachability with no or minimal data plane
impact.

 Thx,
R.