link monitoring and BFD in SDN networks

Mon Jan 19 22:01:40 UTC 2015

Hi,

Routers connected back to back often rely on BFD for link failures. Its
certainly possible that there is a switch between two routers and hence a
link down event on one side is not visible to the other side. So, you run
some sort of an OAM protocol on the two routers so that they can detect
link flaps/failures.

How will this happen in SDN networks where there is no control plane on the
routers. Will the routers be sending a state of all their links to a
central controller who will then detect that a link has gone down. This
just doesnt sound good. I am presuming that some sort of "control plane"
will always be required.

Any pointers here?

Is there any other reason other than link events for which we would need a
control plane on the routers in SDN?

Thanks,
Glen