[mpls] Comment on draft-chen-mpls-p2mp-ingress-protection

["Nobo Akiya (nobo)" <[e-mail]>]

Hi Authors,

I didn't get a chance to comment on your draft at the WG session today, so sending to the list. My concern is similar to what Greg Mirsky stated. Simply running 2 independent BFD sessions (as described in the slides) will have issues.

> 3.  Ingress Failure Detection
> 
>   Exactly how the failure of the ingress (e.g.  R1 in Figure 1) is
>   detected is out of scope for this document.

I believe, at least, definition of the "failure" should be defined in the draft. Without it, it can be interpreted by readers as complete node outage, outage of all involved links, outage of just primary-backup link, or even something else. And without defining what the "failure" is, it's difficult to figure out the right techniques to detect the failure. And that can easily result in deviating detection implementations for described solution to not kick off in expected manner.

-Nobo