Re: [pim] AD Review of draft-ietf-pim-bfd-p2mp-use-case-05

[Alvaro Retana <[e-mail]>]

On August 31, 2021 at 4:51:17 PM, Jeffrey Haas wrote:

Jeff:

Hi!  Thanks for looking at this document!


...
> If I were to re-state the longer version of the draft's name, this is
> effectively "using BFD-MP to let PIM hello procedures fail faster". If
> that's an adequate assessment, perhaps the title might be adjusted a bit.
>
> I think Alvaro's point is that this is really covering a small bit of
> PIM procedure and it sounds like it's intended to be a lot more broad from
> the document title.

Yup, that's the point. :-)


...
> My second concern is shorter. Section 2.3 recommends that the p2mp BFD
> sessions use a TTL of 255 and reference the GTSM procedures in RFC 5881.
> However, since the destination address is a multicast group and the
> underlying PIM protocol uses a TTL of 1 for its messages, I'm not sure the
> 255 is appropriate for this use case.

The draft originally (-05) required using a TTL of 1, but I asked Greg
to change it because both rfc5880/rfc5881 require the use of GTSM --
they don't talk about any exceptions, and rfc8562 doesn't mention TTL
at all.

I find it very hard to justify a change in the BFD requirements; the
BFD documents specify what the BFD behavior is, independent of the
application.  In this case, PIM just benefits from it.

I'm not saying that the requirements can't be changed -- but if we
were going to do that we would need some more discussion in the BFD
WG.


Thanks!

Alvaro.