Re: How are you configuring BFD timers?

[Saku Ytti <saku () ytti fi>]

Why does DWDM imply need of BFD?

DWDM has no problem propagating loss-of-signal and asserting remote failure.

It is of course possible to configure DWDM so that this does not
happen, particularly if you buy protected circuit you might not want
it to happen. But as per usual, you should test that vendor delivers
what you buy.


I think the problem probability of not detecting failure on waves,
dark fibres and copper connections are smaller than the probability of
having issue caused by presence of BFD. I think you need very
unreliably failing link to capitalise on BFD. Radio is good candidate,
switch masked liveliness is good candidate.

Of course you also need to be sure you don't kill your BGP's fast
external failover, by using eBGP multihop on your point-to-point
circuit.

On 21 March 2018 at 18:37, Luke Guillory <lguillory () reservetele com> wrote:
> He's asking because if it was dark the interface would go down when the link was lost and the router would pull 
> routes. But PA to FL would lead me to believe it'll be a wave from some type of DWDM gear which brings us to BFD.
>
>
>
>
>
>
> Luke Guillory
> Vice President – Technology and Innovation
>
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> -----Original Message-----
> From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Alex Lembesis
> Sent: Wednesday, March 21, 2018 11:31 AM
> To: Job Snijders (External); Youssef Bengelloun-Zahr
> Cc: NANOG
> Subject: RE: How are you configuring BFD timers?
>
> To speed up BGP routing convergence.  The (2x) dark fiber links from PA to FL are being used as Layer3 datacenter 
> interconnects, where each datacenter has its own AS.  The DF is also carrying FCIP traffic, so we need failover to be 
> as fast as possible.
>
> Best regards,
>
>
>
> Alex
>
>
>
> -----Original Message-----
> From: Job Snijders (External) [mailto:job () instituut net]
> Sent: Wednesday, March 21, 2018 12:25 PM
> To: Youssef Bengelloun-Zahr
> Cc: Alex Lembesis; NANOG
> Subject: Re: How are you configuring BFD timers?
>
> Silly question perhaps, but why would you do BFD on dark fiber?
>
> Kind regards,
>
> Job
>
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-- 
  ++ytti