Subject: [Last-Call] Tsvart last call review of draft-ietf-sfc-nsh-integrity-06

From: Joseph Touch via Datatracker <[email-masked]>
Date: Sun, 25 Jul 2021 22:04:48 -0700

Reviewer: Joseph Touch
Review result: Not Ready

This document has been reviewed as part of the transport area review team's
ongoing effort to review key IETF documents. These comments were written
primarily for the transport area directors, but are copied to the document's
authors and WG to allow them to address any issues raised and also to the IETF
discussion list for information.

When done at the time of IETF Last Call, the authors should consider this
review as part of the last-call comments they receive. Please always CC
[email-masked] if you reply to or forward this review.

It was very difficult to review this document for IETF transport protocol
considerations.

Although "transport encapsulation" is indicated repeatedly, it is never
referred to directly or described either in this document or its citations. It
appears to be using this term in the sense of RFC8300, which too never defines
it, but uses examples that are more accurately referred to in the IETF as link
layer protocols or either network or link tunnel protocols (IP in IP, GRE,
VXLAN, Ethernet).

Regardless of the fact that this confusion originates in RFC8300, it needs to
be addressed here and corrected before this document can be reviewed to
determine if there are any IETF transport area issues.

The remainder of these notes provide detail of this issue.

-----

The document refers back to RFC8300 to define the NSH itself; that document
discusses transport issues just as vaguely (never mentioning a particular
transport protocol), and when it discusses fragmentation, it refers to section
9 of a document (draft-ietf-rtgwg-dt-encap-02 from 2017) that had expired prior
to the publication of RFC8300.  Because transport fragmentation is, IMO, a
normative issue, this should not have been permitted.

Further, Section 9 of that draft incorrectly recommends reliance on ICMP
feedback to address MTU failures when not under a single operator’s management.
That was widely known even then to be insufficient due to blackholing; this had
motivated PLPMTUD in RFC4821 a full decade earlier. RFC8300 compounds this
error by simply asserting that the operator should ensure that ICMPs are not
blocked, overlooking the need to address when this is not the case.

This document cannot ignore that issue and simply refer to RFC8300 on this
issue.

Note that one of the only places an actual encapsulation protocol is mentioned
is RFC8300, in which Section 5 mentions IP and  Section 6.1 Table 1 describes
VXLAN-GPE, GRE, and Ethernet – all of which are described as “transport
encapsulation”.

If, in fact, IETF transport protocols are being used, at some point the use of
an actual IETF transport protocol should be described (e.g., TCP, UDP, SCTP,
DCCP). At that point, the transport issues would be reviewable. As the document
currently stands, it completely ignores such transport issues and should not
proceed until this is addressed and re-reviewed.

If instead, as I suspect, the term “transport encapsulation” actually refers to
“network layer encapsulation” or “link layer encapsulation” and really implies
some sort of tunnel, there would be no transport area issues to review unless
that tunnel were to include a transport protocol as part of the layers of
encapsulation. If that is the case, the document should be revised to replace
the term “transport” with something that more accurately describes VXLAN-GPE,
GRE, Ethernet, and IP encapsulation using IETF terminology. Note that
draft-ietf-intarea-tunnels never uses the term “transport” except when
referring to the use of IETF transport protocols as a tunnel layer, e.g. (i.e.,
the last sentence of Sec 8 of this doc is incorrect in implying otherwise).

(I would also note that neither this doc nor RFC8300 define “transport
encapsulation” in their terminology; even if they would, they should not
attempt to define it in a way inconsistent with widespread use in the IETF).

---

From: tirumal reddy <[email-masked]>
Date: Wed, 28 Jul 2021 19:38:24 +0530

Thanks Joseph for the detailed comment and explanation. We plan to add the
following text to address the issue:

Note that the term “transport encapsulation” used in this document is
equivalent to the term “tunnel encapsulation” used In [ietf-intarea-tunnel].

Cheers,

-Tiru

---

From: Joe Touch <[email-masked]>
Date: Wed, 28 Jul 2021 21:41:06 -0700

Insufficient.

> On Jul 28, 2021, at 7:09 AM, tirumal reddy <[email-masked]> wrote:
> 
> 
> Thanks Joseph for the detailed comment and explanation. We plan to add the following text to address the issue:
> 
> Note that the term “transport encapsulation” used in this document is equivalent to the term “tunnel encapsulation” used In [ietf-intarea-tunnel]. 
> 
> Cheers,
> -Tiru
> 
>> On Mon, 26 Jul 2021 at 10:34, Joseph Touch via Datatracker <[email-masked]> wrote:
>> Reviewer: Joseph Touch
>> Review result: Not Ready
>> 
> -- 
> last-call mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/last-call

---

From: "Joel M. Halpern" <[email-masked]>
Date: Thu, 29 Jul 2021 11:01:39 -0400

If you want the terminology usage clarified, then what they have 
proposed is sufficient.

If you want to change RFC 8300, this is not the place to do that.

Yours,
Joel

On 7/29/2021 12:41 AM, Joe Touch wrote:
>> On Mon, 26 Jul 2021 at 10:34, Joseph Touch via Datatracker 
>> <[email-masked] <mailto:[email-masked]>> wrote:
>>
>>     Reviewer: Joseph Touch
>>     Review result: Not Ready
>>
>>     [email-masked] <mailto:[email-masked]> if you reply to or
>>     forward this review.
>>

---

From: Joseph Touch <[email-masked]>
Date: Thu, 29 Jul 2021 08:21:01 -0700

Joel,

I performed this review for the transport area.

An IETF document should never attempt to redefine the word “transport” in a single sentence and refer to an unpublished draft (even mine) to explain. It takes more than that.

> On Jul 29, 2021, at 8:01 AM, Joel M. Halpern <[email-masked]> wrote:
> 
> If you want the terminology usage clarified, then what they have proposed is sufficient.
> 

Agreed, but we cannot continue to propagate the error. At a minimum, the sentence should clarify that the term is being used inconsistently with the rest of IETF as a whole and explain what it means in a stand-alone way. That either warrants a separate (even if brief) section or at least a terminology section entry.

Additionally, it is not feasible to review how their approach - which makes packets bigger, necessarily - without understanding how that tunneling works.

Joe

>>> On Mon, 26 Jul 2021 at 10:34, Joseph Touch via Datatracker <[email-masked] <mailto:[email-masked]>> wrote:
>>> 
>>>    Reviewer: Joseph Touch
>>>    Review result: Not Ready
>>>

---

From: "Joel M. Halpern" <[email-masked]>
Date: Thu, 29 Jul 2021 11:44:42 -0400

"Insufficient" is not an acceptable answer from a reviewer.  it is not 
even an acceptable answer from an AD.

I do understand that your review is on behalf of the TSV Area Directors. 
  If you are not willing to be more clear about what (within the 
constraints that we are NOT rewriting 8300) is going to be helpful, then 
we will leave it to the Transport ADs.

We will not play "fetch a rock" / "no not that rock" until you are happy.

Yours,
Joel

On 7/29/2021 11:21 AM, Joseph Touch wrote:
> _______________________________________________
> sfc mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/sfc
>

---

From: Joseph Touch <[email-masked]>
Date: Thu, 29 Jul 2021 09:33:04 -0700

Joel,

> On Jul 29, 2021, at 8:44 AM, Joel M. Halpern <[email-masked]> wrote:
> 
> "Insufficient" is not an acceptable answer from a reviewer.  it is not even an acceptable answer from an AD.

My review is commensurate with the response.

> I do understand that your review is on behalf of the TSV Area Directors.  If you are not willing to be more clear about what (within the constraints that we are NOT rewriting 8300) is going to be helpful, then we will leave it to the Transport ADs.

I did below, when I received engagement commensurate with the review I provided.

> We will not play "fetch a rock" / "no not that rock" until you are happy.

That is your decision; it is mine as to what constitutes a single sentence followup on a review that already provided much more detail than “fetch a rock”. 

Nor will I play “ignore the review and redefine the very term that defines the area providing that review”.

Joe

---

From: "Joel M. Halpern" <[email-masked]>
Date: Thu, 29 Jul 2021 12:45:02 -0400

Authors.  If there is something you see as reasonable and consistent 
with the working groups work that you think would help, please do taht. 
  Otherwise, we will leave this reiew situation for the transport ADs to 
resolve.

Yours,
Joel