link monitoring and BFD in SDN networks

Ronald van der Pol Ronald.vanderPol at
Wed Jan 21 17:22:56 UTC 2015

On Mon, Jan 19, 2015 at 22:55:04 +0000, Dave Bell wrote:

> ""

The 802.1ag code used is open source and available on:

> Of course if you want fast failover, you need to send packets very
> rapidly. Every 250ms is not unreasonable. This is going to cause the
> control plane to get very chatty. Typically on high end routers,
> processes such as BFD are actually ran on line cards as opposed to on
> the routing engine. When a failure is detected this reports up into
> the control plane to trigger a reconvergence event. I see no reason
> why this couldn't occur using SDN.

Exactly. This is something you want to do in hardware, especially
if you want to do fast reroute with the OpenFlow group table.
Problem is that many 1U OpenFlow switches do not support 802.1ag.
We made the propotype mentioned above to show and investigate the
benefits of OAM. The closed "open" networking foundation is supposed
to be working on this, but I don't know the status because their
mailing lists are closed.

In SDN/OpenFlow I think a couple of things are needed:
- configure 802.1ag on the interfaces (via ofconfig?)
- configure OpenFlow paths (e.g. primary and backup) and also create
  forwarding entries for 802.1ag datagrams along those paths
- configure fast reroute with the group table (ofconfig?)
By doing this detection and failover are handled in hardware.


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