Faster OSPF convergence on FortiGate FGCP cluster fail-over

I've been testing a few configuration tweaks in order to reduce my OSPF routing convergence to the bone, a sub second fail-over.

Here are the optimal FortiGate Cluster Protocol settings I've found out:

    config system ha
            ...
            set route-ttl 60
            set route-wait 60
            set route-hold 60
            set hb-interval 1
            set hb-lost-threshold 3
            set hello-holddown 5
            set arps 50
            set arps-interval 1
            set session-pickup enable
            set session-pickup-connectionless enable
            set session-pickup-delay enable
            set link-failed-signal enable
            ...

You will find all the needed information of each parameters here:

https://docs.fortinet.com/document/fortigate/6.0.0/handbook/947938/failover-performance

https://docs.fortinet.com/document/fortigate/6.0.0/handbook/184962/routing-graceful-restart

Graceful restart has to be setup at your dynamic routing protocol, on this lab, OSPF over IPsec is used.

config router ospf
    set router-id 9.9.9.9
    set restart-mode graceful-restart
    config area
        edit 0.0.0.0
        next
    ...

Below is a view behind a Spoke FortiGate reaching the FGCP OSPF router through an IPsec tunnel. The FGCP is conducting a failover due to port10 being brought down on the Master node.

That's it..