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

Joseph Touch <> Thu, 29 July 2021 15:21 UTC

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From: Joseph Touch <>
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Date: Thu, 29 Jul 2021 08:21:01 -0700
Cc: tirumal reddy <>, tsv-art <>,,,
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To: "Joel M. Halpern" <>
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Subject: Re: [Tsv-art] [Last-Call] Tsvart last call review of draft-ietf-sfc-nsh-integrity-06
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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An IETF document should never attempt to redefine the word “transport” in a single sentence and refer to an unpublished draft (even mine) to explain.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 <> wrote:
> 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.

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.


> On 7/29/2021 12:41 AM, Joe Touch wrote:
>> Insufficient.
>>> On Jul 28, 2021, at 7:09 AM, tirumal reddy <> 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 < <>> wrote:
>>>    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
>>> <> 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).
>>> -- 
>>> last-call mailing list
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