How are you configuring BFD timers?

Jason Lixfeld jason+nanog at lixfeld.ca
Wed Mar 21 17:10:53 UTC 2018


A few years ago I did some testing and found that the time between the transceiver detecting LOS and the routing protocol (ISIS in this case) being informed that the link was down (triggering the recalculation) took longer than it took BFD to signal ISIS to recalculate.

> On Mar 21, 2018, at 12:35 PM, Bryan Holloway <bryan at shout.net> wrote:
> 
> Wouldn't any tangible problem on a dark-fiber link result in an interface shutdown, ostensibly creating the trigger one would need to begin re-convergence?
> 
> 
> On 3/21/18 11:31 AM, Alex Lembesis wrote:
>> 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 at 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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