Re: [sfc] New Version Notification for draft-ietf-sfc-multi-layer-oam-03.txt

[Greg Mirsky <[e-mail]>]

Hi Carlos,
please find responses to your questions in-line and tagged GIM>>.

Regards,
Greg

On Fri, May 10, 2019 at 7:53 PM Carlos Pignataro (cpignata) <
[e-mail]> wrote:

> Hi, Greg, SFC,
>
> In order to understand the positioning of draft-ietf-sfc-multi-layer-oam,
> please find 3 high-level yet very important questions and associated
> comments for consideration.
>
> To avoid potential misinterpretation and to be explicit on this note's
> intention: this email does not imply interest in this draft, does not mean
> support, I have not read the document fully.
>
> But a quick note for completeness:
>
> 1. “Implementation Status” Section.
>
> The authors seem to selectively respond to comments.
>
> I asked for an “Implementation Status” Section [RFC7942] at least two or
> three times:
> * March 29, 2018, on draft-wang-sfc-multi-layer-oam
> https://mailarchive.ietf.org/arch/msg/nvo3/eNRV-7GLWO_lLeeXwI97HhTrtBo
> * October 27, 2018, on adoption
> https://mailarchive.ietf.org/arch/msg/sfc/wuK4MiyeOMNbXrRIYjiW7zCtZ70
>
> Instead, this drafts seems to be inventing a full blown protocol without
> implementation practice.
>
> SFC Chairs, could we please follow-up on repeated comments made on the
> list and track a disposition? These are over a year old, and part of an
> adoption call.
>
> Request: Can we please add an “Implementation Status” section?
>
GIM>> As usual, the implementation status will be reflected in the Shepherd
write-up.

>
>
> 2. New protocol invention outside of / rogue to an SFC OAM Framework.
>
> draft-ietf-sfc-multi-layer-oam does not reference any other SFC I-Ds. It
> does not build upon existing work in progress, and instead invents a new
> protocol with RFC8300 as the only Normative reference from SFC.
>
GIM>> Isn't it a contradiction between your statements
"draft-ietf-sfc-multi-layer-oam does not reference any other SFC I-Ds" and
"RFC8300 as the only Normative reference from SFC"?
On the state of the SFC OAM Framework document. I don't recall a discussion
of the draft at any recent SFC WG meeting. Indeed, there were many updates,
plenty of information added that should be reviewed by the WG. At the same
time, contributions to draft-ietf-sfc-multi-layer-oam are always welcome.
Will be glad to discuss them.

>
> The draft-ietf-sfc-oam-framework at
> https://tools.ietf.org/html/draft-ietf-sfc-oam-framework-06 takes a
> holistic approach of including an analysis (selecting only some section
> titles):
> 4.  SFC OAM Functions . . . . . . . . . . . . . . . . . . . . . .   8
> 5.  Gap Analysis  . . . . . . . . . . . . . . . . . . . . . . . .  11
> 5.1.  Existing OAM Functions  . . . . . . . . . . . . . . . . .  11
> 5.2.  Missing OAM Functions . . . . . . . . . . . . . . . . . .  12
> 6.4.  OAM Toolset applicability . . . . . . . . . . . . . . . .  13
>        6.4.1.  ICMP Applicability  . . . . . . . . . . . . . . . . .  13
>
> This analysis ought to guide protocol definition.
>
GIM>> draft-ietf-sfc-oam-framework has not been discussed by the SFC WG
since even though much of material has been added to it.

>
> Question: Can this draft consider existing protocols and gap performed
> before re-inventing? Specifically Normatively cite the SFC OAM Framework
> and see where reuse is best?
>
GIM>> SFC OAM Framework has Informational document track and I don't see a
good reason of making it Normative reference for
draft-ietf-sfc-multi-layer-oam.

>
>
> 3. Existing implementation of OAM functions.
>
> Hows does this draft work with existing OAM functions with existing
> implementation, such as
> https://tools.ietf.org/html/draft-penno-sfc-trace-03 ? The fact that the
> draft is expired does not mean the implementation is uncoded.
>
GIM>> How it can interwork with something that is not fully documented,
which state is unknown, uncertain? The goal of writing, developing
standards is to ensure interoperability among implementations. If someone
is not committed to the development of their solution for the interoperable
multi-vendor environment, then what we can do in such case? You are the
co-author of the draft and I encourage you to re-start the work, bring to
WG for the discussion.

>
>
> Many thanks,
>
> — Carlos Pignataro
>
> On May 9, 2019, at 1:31 AM, Greg Mirsky <[e-mail]> wrote:
>
> Dear All,
> the update to the draft addresses the comment received from Joel at the
> meeting in Prague:
> - Joel: if we get an echo request we can't parse, how do we know that it
> is an echo request, and do we have the information to return it to the
> correct source?
> - Greg: we will clarify this in the draft. It has to practical so the
> sender can understand the situation.. We introduced two classes of TLVs:
> mandatory and optional. Will add clearer text.
>
> A new TLV, Errored TLVs, introduced to be optionally used to pass in an
> echo reply mandatory TLVs that were not understood because either the
> implementation on the receiver does not support them or couldn't parse them
> correctly.
>
> Also, please review the update to the interpretation of O-bit and the
> value of the Next Protocol field to address Adrian's comments at the
> meeting in Bangkok:
> The rules of
>    interpreting the values of O bit and the Next Protocol field are as
>    follows:
>
>    o  O bit set, and the Next Protocol value is not one of identifying
>       active or hybrid OAM protocol (per [RFC7799] definitions), e.g.,
>       defined in this specification Active SFC OAM - a Fixed-Length
>       Context Header or Variable-Length Context Header(s) contain OAM
>       command or data.  and the type of payload determined by the Next
>       Protocol field;
>
>    o  O bit set, and the Next Protocol value is one of identifying
>       active or hybrid OAM protocol - the payload that immediately
>       follows SFC NSH contains OAM command or data;
>
>    o  O bit is clear - no OAM in a Fixed-Length Context Header or
>       Variable-Length Context Header(s) and the payload determined by
>       the value of the Next Protocol field;
>
>    o  O bit is clear and the Next Protocol value is one of identifying
>       active or hybrid OAM protocol MUST be identified and reported as
>       the erroneous combination.  An implementation MAY have control to
>       enable processing of the OAM payload.
>
>    From the above-listed rules follows the recommendation to avoid
>    combination of OAM in a Fixed-Length Context Header or Variable-
>    Length Context Header(s) and in the payload immediately following the
>    SFC NSH because there is no unambiguous way to identify such
>    combination using the O bit and the Next Protocol field.
>
> Regards,
> Greg
>
> ---------- Forwarded message ---------
> From: <[e-mail]>
> Date: Wed, May 8, 2019 at 10:21 PM
> Subject: New Version Notification for draft-ietf-sfc-multi-layer-oam-03.txt
> To: <[e-mail]>, Gregory Mirsky <[e-mail]>, Bhumip
> Khasnabish <[e-mail]>, Wei Meng <[e-mail]
> <meng.wei2@zte..com.cn>>, Cui(Linda) Wang <[e-mail]>
>
>
>
> A new version of I-D, draft-ietf-sfc-multi-layer-oam-03.txt
> has been successfully submitted by Greg Mirsky and posted to the
> IETF repository.
>
> Name:           draft-ietf-sfc-multi-layer-oam
> Revision:       03
> Title:          Active OAM for Service Function Chains in Networks
> Document date:  2019-05-08
> Group:          sfc
> Pages:          18
> URL:
> https://www.ietf.org/internet-drafts/draft-ietf-sfc-multi-layer-oam-03.txt
> Status:
> https://datatracker.ietf.org/doc/draft-ietf-sfc-multi-layer-oam/
> Htmlized:
> https://tools.ietf.org/html/draft-ietf-sfc-multi-layer-oam-03
> Htmlized:
> https://datatracker.ietf.org/doc/html/draft-ietf-sfc-multi-layer-oam
> Diff:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-sfc-multi-layer-oam-03
>
> Abstract:
>    A set of requirements for active Operation, Administration and
>    Maintenance (OAM) of Service Function Chains (SFCs) in networks is
>    presented.  Based on these requirements an encapsulation of active
>    OAM message in SFC and a mechanism to detect and localize defects
>    described.  Also, this document updates RFC 8300 in the definition of
>    O (OAM) bit in the Network Service Header (NSH) and defines how the
>    active OAM message identified in SFC NSH.
>
>
>
>
> Please note that it may take a couple of minutes from the time of
> submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> The IETF Secretariat
>
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