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

tirumal reddy <> Wed, 28 July 2021 14:08 UTC

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From: tirumal reddy <>
Date: Wed, 28 Jul 2021 19:38:24 +0530
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To: Joseph Touch <>
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Subject: Re: [Tsv-art] Tsvart last call review of draft-ietf-sfc-nsh-integrity-06
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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].



On Mon, 26 Jul 2021 at 10:34, Joseph Touch via Datatracker <>

> 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
> 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,
> 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
> 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).