Thanks a lot for your help Atif.

I will test the configuration in my lab environment and post the results.

Thanks again for your help.

Jose

Hi,

and results?

How was the test and have you got sub-second failover?

I am trying to achieve fast convergence with IP fast reroute (IP FRR) without MPLS TE.

The problem is that I don't know how to test it. With ICMP I don't get any packets lost when I shut down the interface

that is forwarding the traffic. But I don't know how to find out the time for reconvergence.

I am using BFD, too, but looks like that I get the same failover time without BFD.

The OSPF timers are these on CRS8 IOS-XR 4.0.3:

timers throttle lsa all 0 20 5000

timers throttle spf 24 24 5000

timers lsa min-arrival 20

Hello,

I you want convergence times of 10-20ms you need MPLS TE.

we also change OSPF timers to have fast IGP convergence, this is the configuration we use based on Cisco recommendations:

!

router ospf

ispf

nsf ietf

mpls ldp sync

timers throttle lsa all 0 20 5000

timers throttle spf 50 50 5000

timers lsa arrival 15

timers pacing flood 15

!

mpls ldp igp sync holddown 60000

!

hope this helps.

Thank you for the config.

We have similar timers, but I deleted timers pacing flood because I read that it is not recommended to change it.

Do you lose a packet after a failover? When I do an ICMP test and after I administravly shut down the forwarding interface no packets get lost, but when I simulate a link down so that I shut down the interface on the other side I lose one packet.

Maybe my understanding of sub-second convergence is wrong, maybe it is ok that a packet gets lost!

OSPF needs only 28msec to steer the traffic over the backup path but I can not measure the link down time detection. 

Hello,

You have to combine other things like:

ip routing protocol purge interface (global configuration)

interface GigabitEthernet x/y

carrier-delay up msec 500

carrier-delay down msec 0

let me know how that works.

Hi,

still one packet loss. I typed carrier-delay on both routers IOS and IOS-XR but "ip routing protocol purge interface" only on IOS because I could not find it on IOS-XR.

I have to say that the router are connected via DWDM and distance is maybe 30km, not sure if this is that important?