Re: Service Redundancy using BFD

[Ashesh Mishra <[e-mail]>]

Hi Ankur,

This is a good proposal to pursue within the BFD-wg.

Couple of comments:

-          BFD can only signal this diag code for the interface that it is monitoring (the IP next hop, MPLS LSP, etc.). You mention per-service (which I assume means per-service-per-interface) failover in the draft but it may be worthwhile defining behavior on per-service-type-per-interface as well.

-          There still needs to be a method for the primary and backup pairs (two BFD end-points on primary service and two on backup service) to communicate with each other (primary-to-primary and backup-to-backup) if the service is active or standby. This is useful in the scenario when the primary cannot communicate with backup nodes (it is a failure condition after all).

Again, at 10k ft, I like the idea of signaling active/standby using BFD.

Cheers,
Ashesh

From: Rtg-bfd <[e-mail]> on behalf of Ankur Dubey <[e-mail]>
Date: Monday, November 27, 2017 at 9:47 PM
To: "[e-mail]" <[e-mail]>
Cc: Reshad Rahman <[e-mail]>, Sami Boutros <[e-mail]>
Subject: Service Redundancy using BFD

Hi all,

Please review and provide comments for the following draft:

https://datatracker.ietf.org/doc/draft-adubey-bfd-service-redundancy/



Summary of draft:

This draft proposes a new BFD diag code via which a node running a BFD session with another node, can inform the other node after a BFD session times out, that it didn’t go down and did live through the failure.

Such notification is useful for a set of nodes providing Active/Standby redundancy. When these nodes are running multiple L2/L3/L4-L7 services  in non-revertive mode of redundancy, the standby node taking over as active for non-revertive services after BFD times out needs to indicate in the BFD packet that it outlived the other failed old active node. The new diag code will be used for this purpose. When this diag code is set in the BFD packets, it will provide an indication to the failed old active node that it MUST NOT activate the non-revertive services when it comes up.

For providing a per service level failover, a node activating certain non-revertive services needs to indicate that it is Active ONLY for those non-revertive services. This can be done by using a unique bitmap where each bit position is uniquely identifying a service. This unique bitmap is configured on all nodes by a network controller. When there is at least one non-revertive service for which a node is not active AND it is active for at least 1 non-revertive service, this node will set bits identifying the active services in the bitmap and send it in the payload of the BFD packet.


Thanks,
--Ankur