Re: How are you configuring BFD timers?

[Thomas Bellman <bellman () nsc liu se>]

On 2018-03-21 17:24, Job Snijders wrote:

> Silly question perhaps, but why would you do BFD on dark fiber?

Simple paranoia perhaps?  Just because you only have layer 1 equipment
(transponders) right now, doesn't guarantee that you won't need to stick
in a layer 2 switch in the path tomorrow, and if you already have BFD
running, you won't forget to add it at that time.

As a real-life example: we have dark fiber from our main campus to
another campus in the neighbouring city, and from there we have dark
fiber to a partner a few kilometers further away.  We run wavelengths
the entire way from the main campus to our partner (being demuxed and
muxed back at the sub-campus).  At one point, the fiber needed to be
rerouted, and then the attenuation became to high for one of the CWDM
wavelengths.  Solution: put an ethernet switch at our sub-campus to
act as a kind of amplifier for that wavelength.

(This was using 120km CWDM gigabit transceivers directly in the routers
at each end.  We have since retired those and use 10 gigabit DWDM with
transponders and EDFA amplifiers.)

Yes, it was a duct-tape solution, but it was cheap and got the work
done. :-)


        /Thomas Bellman

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