Subject: Éric Vyncke's Abstain on draft-ietf-bfd-vxlan-13: (with COMMENT)

From: Éric Vyncke via Datatracker <[email-masked]>
Date: Wed, 22 Jul 2020 05:28:14 -0700

Éric Vyncke has entered the following ballot position for
draft-ietf-bfd-vxlan-13: Abstain

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COMMENT:
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Thank you for the work put into this document and its update. I have cleared
one of my DISCUSS point about TTL = Hop Limit not being 255.

But, the authors and I are in an impasse about the use of IPv4-mapped IPv6
addresses but I do not want to block the document. I change my ballot to
"ABSTAIN" in the sense of "I oppose this document but understand that others
differ and am not going to stand in the way of the others".

BTW, I understood that the use a prefix rather than /32 or /128 was to allow
for entropy (to explore multiple ECMP/LAG paths). BTW2, the right wording is
"IPv4-mapped IPv6 address" and not "IPv4-mapped IPv4 address" as written twice
in the document.

Did you (or actually the authors) also investigate the use of the:
- ::/0 : unspecified address
- 100::/8 the discard prefix used for RTBH RFC 6666
- or even requesting a block out of the 2001::/23 (reserved for IETF special
use)

Previous COMMENTs for archive as they were on revision -09

RFC 5881 (BFD) states that it applies to IPv4/IPv6 tunnels, may I infer that
this document is only required to address the Ethernet encapsulation ? I.e.
specifying the Ethernet MAC addresses?

-- Section 3 --
At first sight, I was surprized by having a BFD session per VXLAN VNI as it
will create some scalability issue, but, I assume that this is to detect
misconfiguration as well. If so, perhaps worth mentionnig the reasoning behind?

In "the inner destination IP address SHOULD" it is unclear whether it is in the
all BFD packets, or only the request one or ... ?

-- Section 4 --
While probably defined in RFC7348, should "FCS" be renamed as "Outer Ethernet
FCS" for consistency with the "Outer Ethernet Header" in figure 2 ?

Why not using the Source MAC address as the Destination MAC address ? This
would ensure that there is no conflict at the expense of "forcing" the
transmission of the frame even if addressed to itself.

Please consider rewriting the section about TTL/Hop Limit as it is not easy to
parse/read.

-- Section 9 --

This section is mainly about IPv4 (RFC 1812). Please address IPv6 as well in
the explanation of packet not being forwarding when addressed to 127/8

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From: Jeffrey Haas <[email-masked]>
Date: Wed, 22 Jul 2020 12:30:43 -0400

Éric,

> draft-ietf-bfd-vxlan-13: Abstain
[...]

Thank you. This will let us continue toward broader IETF review.

> for entropy (to explore multiple ECMP/LAG paths).

This is one possible case, but primarily it is to let the receiving
application have something they can internally "catch" in their packet
intercept code.  Many router vendors implement unusual things in the
loopback network range.

>  BTW2, the right wording is

As noted in a separate thread, we'll address that correction.

> Did you (or actually the authors) also investigate the use of the:

This is my personal comment; the authors are requested to comment as well.

> - ::/0 : unspecified address

This often interacts oddly with socket libraries and likely would not be as
portable as one might want.

> - or even requesting a block out of the 2001::/23 (reserved for IETF special

As you comment in your private reply, the desire is that we never see the
prefix in question in routing.  The loopback network property encodes that
semantic quite nicely - it's completely local to the box in question.

---

I believe that when this thread concludes, we will have closed on last of
the open issues.  Once Greg has done the necessary updates to pull in the
last few issues, I'll update the shepherd report and resubmit to the IESG.

Thanks for your efforts.

-- Jeff