Subject: Re: [Technical Errata Reported] RFC4443 (6153)

From: Töma Gavrichenkov <[email-masked]>
Date: Wed, 21 Oct 2020 03:00:04 +0300

Peace,

On Fri, May 1, 2020 at 2:04 PM RFC Errata System
<[email-masked]> wrote:
> The following errata report has been submitted for RFC4443,
> "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification".

Folks, we're all busy and that's fine, but it's been early May, any follow-ups?

--
Töma

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From: Fernando Gont <[email-masked]>
Date: Wed, 21 Oct 2020 04:09:46 -0300

Здравствуйте, Toma,

> Folks, we're all busy and that's fine, but it's been early May, any follow-ups?

FWIW, it would seem to me this erratum should be approved.

One might argue that the "It should say" part could be simplified by 
simply s/scope/scope zone/, since RFC4443 need not rehash what's in 
RFC4007. But that's mostly a matter of personal preference, and doesn't 
affect the correctness of the erratum you've submitted.

Thanks!

Cheers,
-- 
Fernando Gont
e-mail: [email-masked] || [email-masked]
PGP Fingerprint: 7809 84F5 322E 45C7 F1C9 3945 96EE A9EF D076 FFF1

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From: 神明達哉 <[email-masked]>
Date: Wed, 21 Oct 2020 21:58:44 -0700

At Wed, 21 Oct 2020 04:09:46 -0300,

> affect the correctness of the erratum you've submitted.

I don't have a strong opinion on whether to approve the erratum, but
if we do so, I'd keep this part of the original text: "This condition
can occur only when the scope of the source address is smaller than
the scope of the destination address (e.g., when a packet has a
link-local source address and a global-scope destination address)".
Technically, this text is not necessary to implement this ICMPv6 code
correctly, but it will still help the understanding.

Also, if the motivation of this erratum is this:

  Consider a case when the source IP is link-local and the destination
  is global, yet the routing happens in the same VLAN. Per RFC 4007,
  the packet should be transmitted; however, RFC 4443 allows for an
  ambiguity which is already causing vendors to reject packets in this
  case.

then I'm skeptical about how much the new text helps improve the
situation.  The misunderstanding that "a packet with link-local src or
dst address can never be forwarded by a router in any way" (it can, as
long as the packet would still stay in the same link zone) is quite
common, but I suspect the current text of RFC4443 Section 3.1 is not
the main source of this misunderstanding.  Even if so, I suspect the
new text will help correct the misunderstanding very much; if
correcting the well-known confusion is the purpose of the erratum, I'd
rather make the erratum text more explicit about that point.

--
JINMEI, Tatuya

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From: Töma Gavrichenkov <[email-masked]>
Date: Fri, 23 Oct 2020 00:00:38 +0300

Peace,

On Thu, Oct 22, 2020 at 7:58 AM 神明達哉 <[email-masked]> wrote:
> the scope of the destination address

This particular phrase is actually incorrect.  Scope zone is not
scope, and per 4007 zones, not scopes, should be considered.

--
Töma

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From: 神明達哉 <[email-masked]>
Date: Thu, 22 Oct 2020 14:36:43 -0700

At Fri, 23 Oct 2020 00:00:38 +0300,

> scope, and per 4007 zones, not scopes, should be considered.

RFC 4007 also defines the "size" of the concept of scopes:

   There is a size relationship among scopes:

   o  For unicast scopes, link-local is a smaller scope than global.

   o  For multicast scopes, scopes with lesser values in the "scop"
      subfield of the multicast address (Section 2.7 of [1]) are smaller
      than scopes with greater values, with interface-local being the
      smallest and global being the largest.

The text in RFC4443 I sited perfectly makes sense to me in this
regard.

In any case, whether we compare "scopes" or "scope zones", my point is
that the note of this text is useful and IMO its sense should be kept.

--
JINMEI, Tatuya