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

Joe Touch <> Thu, 29 July 2021 04:41 UTC

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From: Joe Touch <>
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Date: Wed, 28 Jul 2021 21:41:06 -0700
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To: tirumal reddy <>
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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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> 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).
> -- 
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