Re: BFD stability follow-up from IETF-91

[Manav Bhatia <[e-mail]>]

>
> Hi Marc,
>


> > For the echo mechanism to work, do you agree that you would have to
> > continuously send Echos so that you can detect the issue?
>
> that's what I had in mind, yes
>

.. and i dont like this. Are you saying that for each BFD session now you
will run a parallel BFD echo session that would carry the debug data? Your
scaling just went for a toss !!


>
> > Or are you suggesting that once BFD flaps we will start sending Echoes
> > overloaded with debug information to detect the issue?
>
> interesting idea - that would be an alternative use, collecting forensic
> data. Maybe we should support that too!
>

This would help if the flap is deterministic-ally reproducible. If its not,
then how long do you run the Echo BFD? And what happens to the original BFD
session? You run the two parallel-ly?

Cheers, Manav


>
> My biggest problem with the echo idea is so far BFD-over-LAG. But maybe it
> is
> not a real problem, any echo stamping/updating in the forwarding path would
> require an hardware update (or reprogramming, if your hardware allows) and
> in
> this case one could boldly state that the echo packet must leave via the
> ingress port :-)
>
>
> Regards, Marc
>
>
>
>
>
> On Mon, 8 Dec 2014 09:33:05 +0530, Manav Bhatia wrote:
> > Hi Marc,
> >
> >>
> >>
> >> * Greg's echo idea is of course do-able - when you think timestamping in
> >> hardware can be done then it can be done in the forwarding path for
> echos
> >> as
> >> well. Depends on your hardware :-) and on an agreed (minimal) format for
> >> echo. As mentioned BFD echo is not defined/used for multiple BFD
> features,
> >> which limits it's use though.
> >>
> >
> > For the echo mechanism to work, do you agree that you would have to
> > continuously send Echos so that you can detect the issue?
> >
> > Or are you suggesting that once BFD flaps we will start sending Echoes
> > overloaded with debug information to detect the issue?
> >
> > I'd like to understand this before the mailing list sees a barrage of
> > emails. Alternatively, we can also take it offline and only report the
> > summary of our discussion to the list.
> >
> > Cheers, Manav
>