OSPF/BFD reaction time under 1 second

[Patrik Rehuš]

Hello,

In my topology I have 2 parallel connections from one host to the same
destination. The goal is to switch route to another one under 1 second (in
case of broken link). For this I used OSPF with BFD. BFD use 40ms interval
and multiplier is 5, so theoretical switching time to another link should
be 200ms. In the measurements I find out that sometimes it is OK but
sometimes it takes approximately 1 second longer (based on Wireshark it
takes approx. 1,2s to switch). I think that it is due to tick parameter in
OSPF settings, because base on the documentation „The routing table
calculation and clean-up of areas' databases is not performed when a single
link state change arrives. To lower the CPU utilization, it's processed
later at periodical intervals of num seconds. The default value is 1“.

So, in my case I think that this feature destroys ability of BFD to switch
link under 1 second. Is it correct? If yes, is it possible to set lower
value than 1 second or completely disable this feature?

Thank you for your help.



With best regards,

Patrik Rehus
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