[c-nsp] OSPF per-prefix LFA

[George Giannousopoulos]

Hi Mohammad,

It's not one or the other..
With OSPF tuning you improve convergence for sure and as others said, it's
a good practice to do so.
If you also implement LFA, you have an extra bonus in convergence time.

On Tue, Jun 2, 2015 at 11:36 AM, Mohammad Khalil <eng_mssk at hotmail.com>
wrote:

> Hi all
> Thanks for the replies
> Yes Adam it's supported , am using it on a virtual machine :)
> I guess me using virtualized environment might caused the LFA not to work
> the way it should , but what am confused about now is to use LFA or to just
> manipulate the timers ?
>
> Thanks again
>
> BR,
> Mohammad
>
> From: Adam.Vitkovsky at gamma.co.uk
> To: eng_mssk at hotmail.com
> CC: cisco-nsp at puck.nether.net
> Subject: RE: [c-nsp] OSPF per-prefix LFA
> Date: Thu, 28 May 2015 13:43:39 +0000
>
> Hi Mohammad,
>
>
>
> I have never had to tune IGP to get sub 50ms LFA failover times.
>
> The failover times have nothing to do with IGP.
>
> Actually the switchover itself (from primary to backup path) is done in
> couple of usec (microseconds).
>
> So what you need to fight against is actually the time it takes the HW to
> realize there's no light on the link.
>
> As it was suggested already tuning the "carrier-delay down" to 0 is an
> absolute must.
>
>
>
> Yes tuning:
>
> timers throttle lsa,
>
> timers lsa arrival,
>
> timers pacing flood
>
> - is vital to propagate the information across the backbone as fast as
> possible so BGP can switch to backup NH ASAP if primary NH is unreachable.
>
> But that's a different story altogether.
>
>
>
> I think it's really hard to tell what's actually going on in virtual
> environments.
>
> Looks like in your case LFA is really slow so SFP kicks in sooner than LFA
> that's why tuning SPF got you better results.
>
> You might want to check how your virtual environment reports link failures
> (at what time intervals).
>
> Is LFA actually supported on CSR?
>
>
>
> adam
>
>
>
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