Re: How are you configuring BFD timers?

[Youssef Bengelloun-Zahr <bengelly () gmail com>]

Using 200 ms / 200 ms / x3 on either metro dark fiber or longhaul waves
(Paris / Frankfurt / Amsterdam) successfully.

Best regards.

Y.



2018-03-21 16:11 GMT+01:00 Alex Lembesis <Alex.Lembesis () tevapharm com>:

> Using 250ms x 3 on fiber connecting Pennsylvania to Florida...
>
> Best regards,
>
>
>
> Alex
>
> -----Original Message-----
> From: NANOG [mailto:nanog-bounces () nanog org] On Behalf Of Jason Lixfeld
> (External)
> Sent: Wednesday, March 21, 2018 9:10 AM
> To: NANOG
> Subject: How are you configuring BFD timers?
>
> Hey,
>
> For those running BFD on your land-based point-to-point links, I’m
> interested in hearing about what factors you consider when deciding how to
> configure your timers and multiplier.
>
> On paper, BFD between two devices over a local or metro dark fibre or wave
> seems pretty trivial:  Assuming your gear can a) support echo mode b)
> hardware offloads echo processing c) automatically treats echos as vital
> and puts them into the appropriate high priority queue, then setting the
> timers down to their lowest possible values (3ms on some of the gear that
> I’ve seen) and some low multiplier seems more than reasonable.  But?
>
> From another angle, your link isn’t dark fibre or a wave but, for example,
> ethernet over some sort of IP based L2 Transport, and is still a low (sub
> 1ms) one-way latency local or metro link.  How do you set your timers, and
> what do you base that on?
>
> From yet another angle, what if your link is a long-haul wave, or for that
> matter a wave of any distance that imposes a one-way latency that is higher
> than the minimum tx and rx timers that are supported by your gear?  We’ll
> assume an unprotected wave, because I’m sure if it’s protected, you have no
> choice but to consider the one-way latency of the longest of the two
> segments.
>
> I made some assumptions above about support for echo mode and hardware
> offload, but what if (some of) your gear doesn’t support some or all of
> that stuff?  How do you factor your configuration decisions?
>
> Thanks!
>
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