Subject: [mpls] Update on BFD Directed in MPLS network

From: Greg Mirsky <[email-masked]>
Date: Tue, 5 Dec 2017 08:15:58 -0600

Hi Nick, WG Chairs, Carlos, at. al,
we've reviewed Carlos presentation from the Prague meeting
<https://datatracker.ietf.org/meeting/99/materials/slides-99-mpls-sessa-08-2-comments-on-bfd-directed/>.
We greatly appreciate his contribution to improve the solution. Below is
the list of the resolutions to address technical comments:

   - FEC sub-TLVs. Carlos brought up question whether some sub-TLVs listed
   in the Sub-TLVs for TLV Types 1, 16, and 21 sub-registry are applicable:
      - Nil FEC - may be used;
      - PW FEC (FEC 128 and FEC 129) - though BFD over PW VCCV is addressed
      in RFC 5885, nothing precludes, in my opinion, use of PW by egress LSR to
      send BFD control packets;
      - multicast FECs - good point, I agree. To address we've added the
      following text:

   Multicast Target FEC Stack sub-TLVs, i.e. p2mp
   and mp2mp, SHOULD NOT be included into Reverse Path field.  If the
   egress LSR finds multicast Target Stack sub-TLV it MUST send echo
   reply with the received Reverse Path TLV, BFD Discriminator TLV and
   set the Return Code to "Inappropriate Target FEC Stack sub-TLV
   present" Section 3.3.

   - RFC 5884 does not specify Default
      - good point, agree. To address we've applied the following update:

OLD TEXT
If none sub-TLVs found in the BFD Reverse Path TLV, the
egress BFD peer MUST revert to using the default, i.e., over IP
network, reverse path.

NEW TEXT
If none sub-TLVs found in the BFD Reverse Path TLV, the
egress BFD peer MUST revert to using the local policy based
decision as described in Section 7 [RFC5884],
i.e., routed over IP network.

All the above mentioned updates are applied in the recently published
version -08. Appreciate your consideration to progress this document.

Regards,
Greg