Re: [sfc] Regarding last call for draft-ietf-sfc-multi-layer-oam

["Carlos Pignataro (cpignata)" <[e-mail]>]

Hi Joel,

Sorry if I was not clear — I did not mean infer from a packet payload the function type. I meant: look at the O-bit. If set, it is OAM. The NP says how that OAM is encapsulated, which can include IP->ICMP.

Based on that, what part of the definition you feel is unclear? 

From RFC 8300:

   O bit:  Setting this bit indicates an OAM packet (see [RFC6291]).
…
      The O bit MUST be set for OAM packets and MUST NOT be set for
      non-OAM packets.  The O bit MUST NOT be modified along the SFP.


This seems to match what I understand is also your preference.

What exactly is needed to be updated on the definition of the O-bit?

Best,

Carlos.


> On Dec 18, 2021, at 7:48 PM, Joel Halpern Direct <[e-mail]> wrote:
> 
> Just commenting on one aspect of your note.  I think the definition of the SFC NSH header O bit is unclear.  It never occurred to me that one would expect an SFC classifier to not that an inncoming packet was carrying ICMP, look at the ICMP type, decide it was an OAM packet, and set the O bit in the SFC NSH header.  No, nothing in the OAM framework prohibits that.  But nothing leads one to expect it either.
> 
> Thus, I think it is helpful to clarify the meaning of the O-bit. Personally, I rather like saying that the NSH O bit is to indicate the presence of OAM for SFFs.  But my personal view is largely irrelevant.
> 
> It would be good to hear from others in the working group.
> 
> Yours,
> Joel
> 
> On 12/18/2021 5:41 PM, Carlos Pignataro (cpignata) wrote:
>> Dear Greg,
>> Thank you for the reply — please find inline my follow-ups (to the comments you responded to, even though there’s a few you missed or otherwise skipped)
>> As dialogue in this thread seem to be getting intertwined and hard to follow, with several weeks between responses, I will let the chairs (I believe there’s no shepherd assigned) track the issues and review comments (not sure if there’s an issue tracker)and take it from here.
>> Happy Holidays!
>>> 12/15/21 午後8:00、Greg Mirsky <[e-mail] <mailto:[e-mail]>>のメール:
>>> 
>>> Dear Carlos,
>>> please find my notes below in-line under the GIM2>> tag. Attached is the diff highlighting two editorial changes.
>>> 
>>> Regards,
>>> Greg
>>> 
>>> On Fri, Nov 26, 2021 at 8:18 PM Carlos Pignataro (cpignata) <[e-mail] <mailto:[e-mail]>> wrote:
>>> 
>>>    Dear Greg,
>>> 
>>>    I disagree. My perspective is that they go from not helpful to
>>>    plain harmful.
>>> 
>>>    Let’s look at those three aspects one-by-one (changing the
>>>    bulleted list into a numbered list for ease of tracking):
>>> 
>>>     1. This is no different than RFC 8300. The O bit specifies the
>>>        packet being OAM,
>>> 
>>> GIM2>> I don't know of a definition of an "OAM packet". Even more, RFC 8300 does not refer to any such definition, nor does it provide it.  draft-ietf-sfc-multi-layer-oam clarifies the use of O bit for the active SFC NSH OAM.
>> CMP2: I am not sure of the implication of you not knowing that definition, nor do I see this response moving alignment forward.
>> CMP2:From RFC8300:
>> CMP2:      The O bit MUST be set for OAM packets and MUST NOT be set for
>> CMP2:      non-OAM packets.  The O bit MUST NOT be modified along the SFP.
>> CMP2: And RFC8924 includes “OAM packet” 30 times.
>>>     1. the Next Protocol specifies the type of packet which can be
>>>        “Active SFC OAM”
>>>          * Stating however that the identification is based on a
>>>            combination of fields is incorrect.
>>>     2. This is not a generic behavior that needs specifying or
>>>        updating. It is part of the specific NSH Next Protocol value
>>>        behavior for the NSH Next Protocol being defined as “Active
>>>        SFC OAM”.
>>>     3. This is incorrect and a serious over-reach. Specifically:
>>>          * If the O bit is set and the Next protocol is not “Active
>>>            SFC OAM”, the definition is much beyond the scope of this
>>>            document — since this document specifies behaviors for one
>>>            specific SFC OAM protocol which is “One Active SFC OAM”
>>>            (name to be narrowscoped as per other pending thread)
>>> 
>>> GIM2>> I don't see why you re-name the Active SFC OAM protocol into "One Active SFC OAM". That is not what is in the draft. Are you preparing another draft that you believe will update draft-ietf-sfc-multi-layer-oam by introducing an additional active SFC OAM protocol?
>> CMP2: My point is that draft-ietf-sfc-multi-layer-oam is not the only Active SFC OAM protocol.
>> CMP2: RFC8924 includes ICMP, which by simply setting O=1 and NP as IP can be used.
>>>          * If the O bit is set and the Next protocol is not “Active
>>>            SFC OAM”, and this document somehow concludes that the OAM
>>>            is in the Context Header, then it is:
>>>              o Breaking other OAM protocols including other Active
>>>                SFC OAM protocols encapsulated in IPv4, in IPv6, SFC
>>>                Trace. It is valid to have O=1, NSH NP as IPv4, and an
>>>                OAM packet encapsulated. 
>>> GIM2>> Protocols that use IP/UDP encapsulation are not active SFM OAM protocols even though they might be used as such. I expect that if the payload of NSH is an ICMPv6 echo request, the O bit will be cleared and the Next Protocol set to IPv6 value.
>> CMP2: The first sentence is interesting:
>> CMP2: 1. please point to a reference that explains that using a specific encapsulation prevents specific functionality.
>> CMP2: 2. What is a protocol used as active OAM but not being active OAM?
>> CMP2: Regarding the second sentence, thanks for sharing what you expect — however that is different than what specs write :-) Why would encapsulation dictate the value of the O bit? Take for example BFD encapsulated in IP…
>>>              o Breaking the use of context headers, since they need
>>>                context that ought to equally apply to OAMs and to
>>>                data packets, as for example a Flow Label, a
>>>                Forwarding context, etc. Re-writing Context Headers
>>>                breaks that.
>>> 
>>> GIM2>> draft-ietf-sfc-multi-layer-oam does not include any processing that requires re-writing an NSH Context Header.
>> CMP2: Your document says the following:
>> CMP2:          - An SFC NSH Context Header(s) contain an OAM processing
>> CMP2:          instructions or data.
>> CMP2: which prevents using context header for spec’ed context header uses.
>>> 
>>>    I’d encourage the WG, shepherd, and WG Chairs to more closely
>>>    inspect and review this document, specifically whether is defining
>>>    one SFC Active OAM protocol, or breaking functionality while
>>>    redefining base RFC 8300 behavior.
>>> 
>>> 
>>> 
>>>    Although these were brought up before, highlighting a couple of
>>>    comments:
>>> 
>>> 
>>>    1.  Introduction
>>>       Also, this document updates Section 2.2 of [RFC8300] in part of
>>>    the
>>>       definition of O bit in the NSH.
>>> 
>>>    CMP: I do not see the need to redefine the O bit in the NSH.
>>> 
>>> 
>>>    4.  Active OAM Identification in the NSH
>>>       The O bit in the NSH is defined in [RFC8300] as follows:
>>>          O bit: Setting this bit indicates an OAM packet.
>>>       This document updates that definition as follows:
>>>          O bit: Setting this bit indicates an OAM command and/or data in
>>>          the NSH Context Header or packet payload.
>>> 
>>>    CMP: There is, as shown above, no need for this.
>>> 
>>> GIM2>> As a result of RFC 8300 not providing a reference or definition of an "OAM packet", this draft addresses that for the case of Active SFC OAM.
>> CMP2: Thank you for explaining the rational for the O-bit text in your document.
>> CMP2: Please search for “OAM packet” in existing RFCs going back to at least 15 years ago.
>> CMP2: draft-ietf-sfc-multi-layer-oam does not provide the definition (not needed frankly) of what you say needs defining.
>>> 
>>>       *  O bit set and the "Next Protocol" value does not match the value
>>>          Active SFC OAM (TBA1), defined in Section 9.1:
>>>             - An SFC NSH Context Header(s) contain an OAM processing
>>>             instructions or data.
>>> 
>>>    CMP: As shown above, this 1. breaks functionality (e.g., Flow
>>>    Label in context) and 2. has absolutely *no* need to be included
>>>    in this specific OAM protocol document.
>>> 
>>> GIM2>> If there's no NSH Context Header with OAM processing instruction or data, then the O bit will not be set. If one or more NSH Context Header includes OAM processing instructions or data, then, I assume, the O bit will be set. draft-ietf-sfc-multi-layer-oam does not change that. (I much appreciate Frank's comments and the discussion that helped clarify that scenario.)
>> CMP2: Can you please share a reference to OAM in NSH context headers?
>>> 
>>> 
>>>    5.  Active SFC OAM Header
>>> 
>>>       This document defines Active OAM Header
>>>       (Figure 2) to demultiplex active OAM protocols on an SFC.
>>> 
>>>    CMP: The identification of OAM protocols is already solved
>>>    directly in RFC 8300 by using the NSH Next Protocol.
>>>    CMP: This meta-header is redundant at best.
>>> 
>>>          Msg Type - six bits long field identifies OAM protocol,
>>>    e.g., Echo
>>>          Request/Reply or Bidirectional Forwarding Detection.
>>> 
>>>    CMP: First, why would BFD be carried as “One SFC Active OAM
>>>    protocol” -> G-ACh-like meta-header with BFD Msg Type?
>>> 
>>> GIM2>> draft-ietf-sfc-multi-layer-oam does not define how BFD to be carried in NSH environment. Will remove the reference to BFD in the next update.
>> CMP2: Whether you remove it from your draft, it is still another SFC Active OAM Protocol.
>>>    CMP: Second, I believe this also explains that what this document
>>>    is defining is the “Echo Request/Reply” Active OAM Protocol.
>>> 
>>>    CMP: Since the name of the active OAM protocol defined in this
>>>    document is "Echo Request/Reply”, could I please request to:
>>>    CMP: 1. Provide a more specific name (since Echo Request/Reply can
>>>    easily be confused with using ICMP)
>>> 
>>> GIM2>> Throughout the document, "Echo Request/Reply" and "SFC Echo Request/Reply" are used interchangeably. Will add an explicit note to that in the Terminology section.
>> CMP2: Whether there’s a global replace, ICMP can still be another SFC Active OAM Protocol.
>>>    CMP: 2. Rename the title of this document to clearly define its
>>>    scope for one specific SFC Active OAM protocol, by name, and not
>>>    all Active OAM Protocols?
>>> 
>>> GIM2>> The document provides the framework for Active SFC OAM and defines SFC Echo Request/Reply protocol. I will gladly update the title of the document, the WG decides that is necessary.
>> CMP2: What you write immediately above does not match the Abstract of draft-ietf-sfc-multi-layer-oam.
>> CMP2: And again, the only time the word “Framework appears in this draft is as part of the Citation for RFC8924! :-)
>> CMP2: No other framework needed.
>> CMP2: The Abstract says “requirements”, "an encapsulation”, "a mechanism to detect and localize defects”… you say now a “framework” and “a protocol”.
>> Best,
>> Carlos.
>>> 
>>> 
>>>    Best,
>>> 
>>>    Carlos.
>>> 
>>>>    On Nov 26, 2021, at 10:30 PM, Greg Mirsky <[e-mail]
>>>>    <mailto:[e-mail]>> wrote:
>>>> 
>>>>    Dear Carlos,
>>>>    I believe that the proposed new text clarifies several aspects of
>>>>    O bit:
>>>> 
>>>>      * active SFC NSH OAM packet is identified by the combination of
>>>>        O bit set and the value of the NSH' Next Protocol field is
>>>>        Active SFC OAM;
>>>>      * the combination of O bit clear and the Next Protocol set to
>>>>        the Active SFC OAM value - erroneous and must be reported;
>>>>      * O bit set and the Next Protocol is not Active SFC OAM -
>>>>        Context Header(s) include OAM processing instructions or data.
>>>> 
>>>>    Would you agree that these are helpful clarifications?
>>>> 
>>>>    Regards,
>>>>    Greg
>>>> 
>>>>    On Fri, Nov 26, 2021 at 7:10 PM Carlos Pignataro (cpignata)
>>>>    <[e-mail] <mailto:[e-mail]>> wrote:
>>>> 
>>>>        Thank you Frank and Greg — what is the actual behavioral
>>>>        change in the proposed redefinition of the O-bit from the
>>>>        processing and rules defined in RFC8300?
>>>> 
>>>>        Thanks,
>>>> 
>>>>        Carlos.
>>>> 
>>>>>        On Nov 26, 2021, at 4:09 PM, Frank Brockners (fbrockne)
>>>>>        <fbrockne=[e-mail]
>>>>>        <mailto:fbrockne=[e-mail]>> wrote:
>>>>> 
>>>>>        Hi Carlos,____
>>>>>        __ __
>>>>>        Personally I don’t see a strong need to evolve the
>>>>>        definition of the O-bit – but if the working group decides
>>>>>        to do so, IMHO it would be good to ensure that the O-bit
>>>>>        indeed signals the fact that active OAM information related
>>>>>        to NSH is carried.____
>>>>>        __ __
>>>>>        Cheers, Frank____
>>>>>        __ __
>>>>>        *From:*Carlos Pignataro (cpignata)
>>>>>        <cpignata=[e-mail]
>>>>>        <mailto:cpignata=[e-mail]>>
>>>>>        *Sent:*Tuesday, 23 November 2021 15:44
>>>>>        *To:*Frank Brockners (fbrockne) <[e-mail]
>>>>>        <mailto:[e-mail]>>
>>>>>        *Cc:*Greg Mirsky <[e-mail]
>>>>>        <mailto:[e-mail]>>; Gyan Mishra
>>>>>        <[e-mail] <mailto:[e-mail]>>;
>>>>>        James N Guichard <[e-mail]
>>>>>        <mailto:[e-mail]>>;[e-mail]
>>>>>        <mailto:[e-mail]>; Joel Halpern Direct
>>>>>        <[e-mail] <mailto:[e-mail]>>
>>>>>        *Subject:*Re: [sfc] Regarding last call for
>>>>>        draft-ietf-sfc-multi-layer-oam____
>>>>>        __ __
>>>>>        Frank, Greg,____
>>>>>        __ __
>>>>>        Do you see a reason to redefine the O-bit?____
>>>>>        __ __
>>>>>        Thanks,____
>>>>>        __ __
>>>>>        Carlos.____
>>>>> 
>>>>> 
>>>>>        ____
>>>>> 
>>>>>            11/23/21午前9:33、Frank Brockners (fbrockne)
>>>>>            <fbrockne=[e-mail]
>>>>>            <mailto:fbrockne=[e-mail]>>のメール:____
>>>>>            __ __
>>>>>            Hi Greg,____
>>>>>            ____
>>>>>            Thanks for the quick reply. Please see inline.____
>>>>>            ____
>>>>>            *From:*Greg Mirsky <[e-mail]
>>>>>            <mailto:[e-mail]>>
>>>>>            *Sent:*Monday, 22 November 2021 23:16
>>>>>            *To:*Frank Brockners (fbrockne) <[e-mail]
>>>>>            <mailto:[e-mail]>>
>>>>>            *Cc:*Carlos Pignataro (cpignata)
>>>>>            <cpignata=[e-mail]
>>>>>            <mailto:cpignata=[e-mail]>>; Gyan
>>>>>            Mishra <[e-mail]
>>>>>            <mailto:[e-mail]>>; James N Guichard
>>>>>            <[e-mail]
>>>>>            <mailto:[e-mail]>>;[e-mail]
>>>>>            <mailto:[e-mail]>; Joel Halpern Direct
>>>>>            <[e-mail]
>>>>>            <mailto:[e-mail]>>
>>>>>            *Subject:*Re: [sfc] Regarding last call for
>>>>>            draft-ietf-sfc-multi-layer-oam____
>>>>>            ____
>>>>>            Hi Frank,____
>>>>>            thank you for your comment describing an interesting
>>>>>            IOAM use case in SFC NSH. I've thought about this case
>>>>>            and I have several questions. I greatly appreciate your
>>>>>            help clarifying them to me:____
>>>>> 
>>>>>              * Is it envisioned that the IOAM can be part of NSH
>>>>>                payload but not to immediately follow the SFC NSH?
>>>>>                Perhaps such a case can be referred to as "IOAM
>>>>>                inside NSH payload" to differentiate from "IOAM on
>>>>>                top of NSH payload"? For example, assuming that the
>>>>>                client payload is IPv6, then NSH is followed by an
>>>>>                IPv6 packet, which, in turn, is followed by IOAM. ____
>>>>>              * If IOAM inside NSH payload is a viable use case,
>>>>>                which SFC element is the intended addressee - SFF or
>>>>>                SF/SF Proxy? If it is the former, what are the
>>>>>                requirements for an SFF to handle this scenario? If
>>>>>                it is the latter, what happens with the client
>>>>>                packet if an SF/SF Proxy does  not support IOAM in
>>>>>                NSH but only NSH per RFC 8300?____
>>>>> 
>>>>>            …FB: The scenario that you outline, i.e. NSH over “IPv6
>>>>>            with IOAM encapsulation”, sounds valid to me; and it
>>>>>            could even be that NSH would also leverage IOAM, in
>>>>>            which case, it would become a case of “IOAM Layering” as
>>>>>            described
>>>>>            inhttps://datatracker.ietf.org/doc/html/draft-ietf-ippm-ioam-deployment-00#section-7.2
>>>>>            <https://datatracker.ietf.org/doc/html/draft-ietf-ippm-ioam-deployment-00#section-7.2>.
>>>>>            As outlined in the draft-ietf-ippm-ioam-deployment,
>>>>>            IOAM-Data-Fields are specific to the layer (and the
>>>>>            associated protocol) that they’re encapsulated into. As
>>>>>            such, in the case of NSH over “IPv6 with IOAM
>>>>>            encapsulation” it would be the IPv6 forwarder that would
>>>>>            handle the IOAM processing. SFF/SF would be
>>>>>            orthogonal/ships-in-the night.____
>>>>>            I've looked through draft-ietf-sfc-ioam-nsh but I
>>>>>            couldn't find answers to these questions (I admit, I
>>>>>            could have missed it).____
>>>>>            Also, I think that your suggestion to avoid any
>>>>>            reference to a hybrid OAM protocol concentrating on the
>>>>>            active OAM identification in the update to O-bit
>>>>>            definition is logical and reasonable. Below, please find
>>>>>            the proposed update:____
>>>>>            OLD TEXT:____
>>>>>               *  O bit set and the "Next Protocol" value does not
>>>>>            match one of____
>>>>>                  identifying active or hybrid OAM protocols (per
>>>>>            classification____
>>>>>                  defined in [RFC7799]), e.g., defined in Section
>>>>>            9.1 Active SFC OAM____
>>>>>                  (TBA1).____
>>>>>            ____
>>>>>                     - a Fixed-Length Context Header or
>>>>>            Variable-Length Context____
>>>>>                     Header(s) contain an OAM command or data.____
>>>>>            ____
>>>>>                     - the "Next Protocol" field determines the type
>>>>>            of payload.____
>>>>>            ____
>>>>>               *  O bit set and the "Next Protocol" value matches
>>>>>            one of identifying____
>>>>>                  active or hybrid OAM protocols:____
>>>>>            ____
>>>>>                     - the payload that immediately follows the NSH
>>>>>            MUST contain an____
>>>>>                     OAM command or data.____
>>>>>            ____
>>>>>               *  O bit is clear:____
>>>>>            ____
>>>>>                     - no OAM in a Fixed-Length Context Header or
>>>>>            Variable-Length____
>>>>>                     Context Header(s).____
>>>>>            ____
>>>>>                     - the payload determined by the "Next Protocol"
>>>>>            field MUST be____
>>>>>                     present.____
>>>>>            ____
>>>>>               *  O bit is clear, and the "Next Protocol" field
>>>>>            identifies active or____
>>>>>                  hybrid OAM protocol MUST be identified and
>>>>>            reported as an____
>>>>>                  erroneous combination.  An implementation MAY have
>>>>>            control to____
>>>>>                  enable processing of the OAM payload.____
>>>>>            ____
>>>>>            NEW TEXT:____
>>>>>            ____
>>>>>            …FB: The new text looks better. Couple of additional
>>>>>            thoughts inline below.____
>>>>>            ____
>>>>>               *  O bit set and the "Next Protocol" value does not
>>>>>            match defined in____
>>>>>                  Section 9.1 Active SFC OAM (TBA1).____
>>>>>            ____
>>>>>            …FB: The above sentence doesn’t sound complete. Likely
>>>>>            you wanted to say something like “O bit set and the
>>>>>            "Next Protocol" value does not matchany of the SFC Next
>>>>>            Protocol values definedefined in Section 9.1 Active SFC
>>>>>            OAM (TBA1).”____
>>>>>            ____
>>>>>            ____
>>>>>                     - a Fixed-Length Context Header or
>>>>>            Variable-Length Context____
>>>>>                     Header(s) contain an OAM command or data.____
>>>>>            ____
>>>>>            …FB: Given that it applies to both, fixed and variable –
>>>>>            how about simplifying to “Context-header(s) that contain
>>>>>            active OAM commands and/or data.”____
>>>>>            ____
>>>>>                     - the "Next Protocol" field determines the type
>>>>>            of payload.____
>>>>>            ____
>>>>>               *  O bit set and the "Next Protocol" value matches
>>>>>            Active SFC OAM____
>>>>>                  (TBA1) value:____
>>>>>            ____
>>>>>                     - the payload that immediately follows the NSH
>>>>>            MUST be the____
>>>>>                     Active OAM Header (Section 5).____
>>>>>            ____
>>>>>               *  O bit is clear:____
>>>>>            ____
>>>>>                     - no OAM in a Fixed-Length Context Header or
>>>>>            Variable-Length____
>>>>>                     Context Header(s).____
>>>>>            …FB: Similar to the note above, “No Context-header(s)
>>>>>            that contain active OAM commands and/or data.” might be
>>>>>            simpler____
>>>>>            ____
>>>>>                     - the payload determined by the "Next Protocol"
>>>>>            field MUST be____
>>>>>                     present.____
>>>>>            ____
>>>>>            …FB: Isn’t this obvious? The reader might wonder why
>>>>>            this is even stated. IMHO we could safely remove this
>>>>>            bullet.____
>>>>>            ____
>>>>>               *  O bit is clear, and the "Next Protocol" field is
>>>>>            set to Active SFC____
>>>>>                  OAM (TBA1) MUST be identified and reported as an
>>>>>            erroneous____
>>>>>                  combination.  An implementation MAY have control
>>>>>            to enable____
>>>>>                  processing of the OAM payload.____
>>>>>            ____
>>>>>            …FB: Just cosmetic, but it would be good to stay with
>>>>>            the pattern of “condition: action” of this paragraph,
>>>>>            e.g.____
>>>>>            ____
>>>>>            * O but is clear andthe "Next Protocol" field is set to
>>>>>            Active SFC____
>>>>>                  OAM (TBA1):____
>>>>>            ____
>>>>>               - Erroneous combination. The combination MUST be
>>>>>            identified and reported.
>>>>> 
>>>>> 
>>>>>            ____
>>>>>            In addition, what would be good,  is to expand a bit on
>>>>>            how that reporting is supposed to happen – as well as
>>>>>            what is supposed to happen with the packet that contains
>>>>>            the erroneous combination. Is it going to be forwarded
>>>>>            or dropped? Is the node detecting the error supposed to
>>>>>            remove the active IOAM header, etc., …?____
>>>>>            ____
>>>>>            Thanks again, Frank____
>>>>>            ____
>>>>>            ____
>>>>>            I hope that the proposed update addresses your concern.____
>>>>>            ____
>>>>>            Regards,____
>>>>>            Greg____
>>>>>            ____
>>>>>            On Mon, Nov 22, 2021 at 11:56 AM Frank Brockners
>>>>>            (fbrockne) <[e-mail]
>>>>>            <mailto:[e-mail]>> wrote:____
>>>>> 
>>>>>                ____
>>>>>                Just saw this thread – and the section on the O-bit
>>>>>                in section 4 caught might attention.____
>>>>>                ____
>>>>> 
>>>>>                   *  O bit is clear, and the "Next Protocol" field
>>>>>                identifies active or____
>>>>> 
>>>>>                      hybrid OAM protocol MUST be identified and
>>>>>                reported as an____
>>>>> 
>>>>>                      erroneous combination.  An implementation MAY
>>>>>                have control to____
>>>>> 
>>>>>                      enable processing of the OAM payload.____
>>>>> 
>>>>>                Per what is mentioned below, the statement
>>>>>                contradicts the principles of IOAM operation. A
>>>>>                packet with O-bit cleared can very well have a
>>>>>                hybrid OAM protocol in the next protocol field. IOAM
>>>>>                is classified as a “Hybrid Type I” protocol per RFC
>>>>>                7799.
>>>>>                A key objective of IOAM is to trace packets through
>>>>>                the network as if they weren’t observed, i.e., the
>>>>>                packet forwarding operation of a packet with IOAM is
>>>>>                expected to be that of a plain packet, i.e., a
>>>>>                packet without IOAM. Consequently,
>>>>>                draft-ietf-sfc-ioam-nsh states clearly that the
>>>>>                O-bit isn’t changed when IOAM is added to an
>>>>>                NSH-tagged
>>>>>                packet:https://datatracker.ietf.org/doc/html/draft-ietf-sfc-ioam-nsh#section-4.2
>>>>>                <https://datatracker.ietf.org/doc/html/draft-ietf-sfc-ioam-nsh#section-4.2>____
>>>>>                ____
>>>>>                I’d strongly suggest to re-word section 4 to either
>>>>>                avoid the reference to “hybrid IOAM” entirely, or to
>>>>>                explicitly list which hybrid OAM approaches the
>>>>>                section applies to – and that way ensure, that IOAM
>>>>>                is not affected. An even simpler approach would be –
>>>>>                as discussed below – so simply avoid the
>>>>>                redefinition of the O-Bit.____
>>>>>                ____
>>>>> 
>>>>>                Thanks, Frank____
>>>>> 
>>>>>                ____
>>>>>                ____
>>>>>                *From:*sfc <[e-mail]
>>>>>                <mailto:[e-mail]>>*On Behalf Of*Carlos
>>>>>                Pignataro (cpignata)
>>>>>                *Sent:*Monday, 22 November 2021 00:52
>>>>>                *To:*Gyan Mishra <[e-mail]
>>>>>                <mailto:[e-mail]>>
>>>>>                *Cc:*James N Guichard
>>>>>                <[e-mail]
>>>>>                <mailto:[e-mail]>>; Greg
>>>>>                Mirsky <[e-mail]
>>>>>                <mailto:[e-mail]>>;[e-mail]
>>>>>                <mailto:[e-mail]>; Joel Halpern Direct
>>>>>                <[e-mail]
>>>>>                <mailto:[e-mail]>>
>>>>>                *Subject:*Re: [sfc] Regarding last call for
>>>>>                draft-ietf-sfc-multi-layer-oam____
>>>>>                ____
>>>>>                Hi, Gyan,____
>>>>>                ____
>>>>>                Thank you for your response!____
>>>>>                ____
>>>>>                On #1, I recall LIME (I co-chaired), but there’s no
>>>>>                “LIME” reference in draft-ietf-sfc-multi-layer-oam,
>>>>>                not I see the relationship. The draft you quote on
>>>>>                https://datatracker.ietf.org/doc/html/draft-ww-opsawg-multi-layer-oam-02
>>>>>                <https://datatracker.ietf.org/doc/html/draft-ww-opsawg-multi-layer-oam-02> seems
>>>>>                to have expired many years ago. ____
>>>>>                ____
>>>>>                Further, Greg Mirsky wrote that it was for
>>>>>                “Historical” reasons. Which one is it?____
>>>>>                ____
>>>>>                On #2, thanks for suggesting that section to be
>>>>>                added. I agree.____
>>>>>                ____
>>>>>                On #3, thanks for the description of the various
>>>>>                sections of draft-ietf-sfc-multi-layer-oam.____
>>>>>                ____
>>>>>                For the record I still do not see how foundational
>>>>>                changes like the O-bit redefinition are needed.____
>>>>>                While you write that "trace an SFP” is a new
>>>>>                functionality, there’s open source running code I-D
>>>>>                documented tools which do that.____
>>>>>                ____
>>>>>                Best,____
>>>>>                ____
>>>>>                Carlos.____
>>>>>                ____
>>>>> 
>>>>>                ____
>>>>> 
>>>>>                    11/20/21午前10:36、Gyan Mishra
>>>>>                    <[e-mail]
>>>>>                    <mailto:[e-mail]>>のメール:____
>>>>>                    ____
>>>>>                    Hi Carlos____
>>>>>                    ____
>>>>>                    Many Thanks for your feedback____
>>>>>                    ____
>>>>>                    Responses in-line____
>>>>>                    ____
>>>>>                    On Fri, Nov 19, 2021 at 11:39 PM Carlos
>>>>>                    Pignataro (cpignata) <[e-mail]
>>>>>                    <mailto:[e-mail]>> wrote:____
>>>>> 
>>>>>                        Dear Gyan,____
>>>>>                        ____
>>>>>                        I hope all is well!____
>>>>>                        ____
>>>>>                        Could I please ask three short clarifying
>>>>>                        questions, follow-ons on your statement
>>>>>                        below?____
>>>>>                        ____
>>>>>                        1. When you write "/with an
>>>>>                        Active Multi layer OAM model/”, can you
>>>>>                        please explain what exactly is “Multi layer”
>>>>>                        about this “OAM model”, and why is
>>>>>                        important? You highlight it in your top-post
>>>>>                        but I cannot find that text in the draft.____
>>>>>                        ____
>>>>>                        When I asked your co-author Greg Mirsky, he
>>>>>                        said:____
>>>>> 
>>>>>                                Additionally, I wonder: Why the file
>>>>>                                name “sfc-multi-layer-oam”?____
>>>>> 
>>>>>                            GIM>> It is historical. ____
>>>>> 
>>>>>                        OAM has historic connotations but for good
>>>>>                        technical reasons as called multi layer as
>>>>>                        it provides a different job of managing
>>>>>                        different layers of the network thus the
>>>>>                        nomenclature “multi layer”____
>>>>> 
>>>>>                    ____
>>>>>                    We can add some verbiage to the draft as we have
>>>>>                    the draft and file name with “multi layer” in
>>>>>                    the name.____
>>>>>                    ____
>>>>>                    LIME is a concluded WG on OAM that has discuss
>>>>>                    the OAM management of the various layers of the
>>>>>                    network.____
>>>>>                    ____
>>>>>                    https://datatracker.ietf.org/wg/lime/about/
>>>>>                    <https://datatracker.ietf.org/wg/lime/about/>____
>>>>>                    ____
>>>>>                    OPSWG has this draft which hones in on the multi
>>>>>                    layer OAM aspects of PM and Fault management of
>>>>>                    SFC. ____
>>>>>                    https://datatracker.ietf.org/doc/html/draft-ww-opsawg-multi-layer-oam-02
>>>>>                    <https://datatracker.ietf.org/doc/html/draft-ww-opsawg-multi-layer-oam-02>____
>>>>>                    ____
>>>>>                    This draft talks about a transport independent
>>>>>                    OAM where OAM mechanisms are data plane
>>>>>                    transport dependent thus the concept of multi
>>>>>                    layer OAM requirements of multiple discrete
>>>>>                    layers of OAM to map to each layer of the
>>>>>                    network. This document also talks about E2E OAM
>>>>>                    inter layer OAM considerations in SFC as the
>>>>>                    fault may occur with the service functions at
>>>>>                    different OSI layers being chained and different
>>>>>                     network layers.____
>>>>>                    ____
>>>>>                    ____
>>>>> 
>>>>>                        ____
>>>>>                        2. When you write "/fills a crucial gap for
>>>>>                        operators/”, are you aware of interoperable
>>>>>                        implementations (which I expect is what
>>>>>                        operators need for it to be useful in an
>>>>>                        actual deployment)? Perhaps an RFC 7942
>>>>>                        "Implementation Status” section could be
>>>>>                        added?____
>>>>> 
>>>>>                    ____
>>>>>                    Gyan> I am not aware of any implementations
>>>>>                    however Ican review with the authors on adding
>>>>>                    the section.  Thank you____
>>>>> 
>>>>>                        ____
>>>>>                        ____
>>>>>                        3. When you write “/for
>>>>>                        new OAM functionality/”, could you please
>>>>>                        clearly describe or explicitly enumerate the
>>>>>                        specific *new* functionality you refer to,
>>>>>                        on top of what existing OAMs provide, and
>>>>>                        how you find that crucial, specifically?____
>>>>> 
>>>>>                    ____
>>>>>                    Troubleshooting SFC is a complex tax for
>>>>>                    operators and having additional OAM capabilities
>>>>>                    that can provide value to operators in E2E SFC
>>>>>                    troubleshooting is a major gain for operators.____
>>>>>                    ____
>>>>>                    RFC 8924 defines the base specification for SFC
>>>>>                    OAM, requirements analysis and generically
>>>>>                    existing OAM mechanisms used at various layers
>>>>>                     and how they can apply to SFC defined in
>>>>>                    section 7. ____
>>>>>                    ____
>>>>>                    This draft provides a comprehensive SFC OAM
>>>>>                    solution and takes the base SFC OAM RFC 8924 and
>>>>>                    existing network layer mechanisms and applies
>>>>>                    them to SFC OAM localized SFC fault isolation
>>>>>                    with a  new Active OAM header, Authenticated
>>>>>                    Echo Request/Reply message and Source TLV. ____
>>>>>                    ____
>>>>>                    The new functionality in this draft is defining
>>>>>                    a new procedure  for Active OAM message on RSP
>>>>>                    in NSH updating NSH RFC 8300 definition of the O
>>>>>                    bit which indicates an OAM command and/or data
>>>>>                    in NSH header or packet payload discussed in
>>>>>                    section 4. ____
>>>>>                    ____
>>>>>                    Section 5  talks about the issue related to
>>>>>                    additional IP/UDP headers in an IPv6 network
>>>>>                    adds noticeable overhead and this draft defines
>>>>>                    a new active OAM header to demultiplex Active
>>>>>                    OAM protocols on an SFC.____
>>>>>                    ____
>>>>>                    Section 6 defines a new Active OAM based
>>>>>                    Authenticated  Echo Request/Reply message for
>>>>>                    SFC that addresses additional requirements, fate
>>>>>                    sharing, monitoring of continuity between SFPs,
>>>>>                    RDI by ingress to egress, connectivity
>>>>>                    verification, fault localization and tracing to
>>>>>                    discover RSP and finally on-demand FM with
>>>>>                    response back to initiator. ____
>>>>>                    ____
>>>>>                    This draft also provides OAM integrity check
>>>>>                    with authentication of request/reply message in
>>>>>                    conjunction with use of source TLV to prevent
>>>>>                    DDOS attack vector with SFC OAM.____
>>>>>                    ____
>>>>>                    The critical new functionality provided for
>>>>>                    operators with Active OAM is the honed in focus
>>>>>                    on troubleshooting continuity of an SFP, trace
>>>>>                    an SFP , consistency verification of SFP and
>>>>>                    fault isolation and localizing of a failure
>>>>>                    within an SFP as well as valuable SFF record
>>>>>                    TLV, SFF information TLV/Sub-TLV  for multiple
>>>>>                    SFs as hops of SFP or multiple SFs for load
>>>>>                    balancing using SFP consistency verification
>>>>>                    procedures.____
>>>>>                    ____
>>>>>                    Many Thanks!!____
>>>>>                    ____
>>>>>                    Gyan____
>>>>> 
>>>>>                        ____
>>>>>                        ____
>>>>>                        Many thanks in advance, I am just trying to
>>>>>                        understand.____
>>>>>                        ____
>>>>>                        Best,____
>>>>>                        ____
>>>>>                        Carlos.____
>>>>> 
>>>>>                        ____
>>>>> 
>>>>>                            11/19/21午後11:02、Gyan Mishra
>>>>>                            <[e-mail]
>>>>>                            <mailto:[e-mail]>>のメール:____
>>>>> 
>>>>>                            ____
>>>>>                            ____
>>>>>                            Dear Chairs & All ____
>>>>>                            ____
>>>>>                            As co-author I support publication of
>>>>>                            this draft. ____
>>>>>                            ____
>>>>>                            This specification fills a crucial gap
>>>>>                            for operators for new OAM functionality,
>>>>>                            with an Active Multi layer OAM model, by
>>>>>                            defining extensibility with
>>>>>                            Active OAM messages, in NSH,  to
>>>>>                            troubleshoot faults in the data
>>>>>                            plane SFC forwarding plane, SFP E2E path
>>>>>                            in the service plane framework.____
>>>>>                            ____
>>>>>                            Kind Regards ____
>>>>>                            ____
>>>>>                            Gyan____
>>>>>                            Verizon ____
>>>>>                            ____
>>>>>                            On Fri, Nov 19, 2021 at 8:33 PM Carlos
>>>>>                            Pignataro (cpignata)
>>>>>                            <cpignata=[e-mail]
>>>>>                            <mailto:[e-mail]>>
>>>>>                            wrote:____
>>>>> 
>>>>>                                Dear Greg,____
>>>>>                                ____
>>>>>                                Thank you for replying to my email.
>>>>>                                Please find a couple follow-ups
>>>>>                                inline, as I invite other WG
>>>>>                                interested parties to the
>>>>>                                discussion.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                    11/19/21午後7:11、Greg Mirsky
>>>>>                                    <[e-mail]
>>>>>                                    <mailto:[e-mail]>>
>>>>>                                    のメール:____
>>>>>                                    ____
>>>>>                                    Dear Carlos,____
>>>>>                                    thank you for your
>>>>>                                    thorough review and detailed
>>>>>                                    comments. Please find responses
>>>>>                                    in-lined below under the GIM>>
>>>>>                                    tag.____
>>>>>                                    ____
>>>>>                                    Regards,____
>>>>>                                    Greg (on behalf of the authors)____
>>>>>                                    ____
>>>>>                                    On Sat, Nov 13, 2021 at 11:50 PM
>>>>>                                    Carlos Pignataro (cpignata)
>>>>>                                    <[e-mail]
>>>>>                                    <mailto:[e-mail]>>
>>>>>                                    wrote:____
>>>>> 
>>>>>                                        Hello, WG,____
>>>>>                                        ____
>>>>>                                        In
>>>>>                                        reviewing draft-ietf-sfc-multi-layer-oam-16,
>>>>>                                        I find that the issues
>>>>>                                        listed below are such that I
>>>>>                                        cannot support publication.____
>>>>>                                        ____
>>>>>                                        Observing what appears to be
>>>>>                                        a single non-author response
>>>>>                                        to the original WGLC email,
>>>>>                                        and one more after this
>>>>>                                        extension, I also perceive
>>>>>                                        the energy level to work on
>>>>>                                        this to be low.____
>>>>>                                        ____
>>>>>                                        Please find some review
>>>>>                                        comments and observations, I
>>>>>                                        hope these are useful:____
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                                        Active OAM
>>>>>                                        for Service Function Chaining____
>>>>> 
>>>>>                                                                                                  draft-ietf-sfc-multi-layer-oam-16____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        Abstract____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           A set of requirements for
>>>>>                                        active Operation,
>>>>>                                        Administration, and____
>>>>> 
>>>>>                                           Maintenance (OAM) of
>>>>>                                        Service Function Chains
>>>>>                                        (SFCs) in a network is____
>>>>> 
>>>>>                                           presented in this
>>>>>                                        document.  Based on these
>>>>>                                        requirements, an____
>>>>> 
>>>>>                                           encapsulation of active
>>>>>                                        OAM messages in SFC and a
>>>>>                                        mechanism to detect____
>>>>> 
>>>>>                                           and localize defects are
>>>>>                                        described.____
>>>>> 
>>>>>                                        ____
>>>>>                                        First, a generic comment on
>>>>>                                        the whole document: Even
>>>>>                                        though the WG produces an
>>>>>                                        SFC OAM framework
>>>>>                                        in rfc8924, I cannot find
>>>>>                                        exactly how
>>>>>                                        draft-ietf-sfc-multi-layer-oam
>>>>>                                        follows or maps to such
>>>>>                                        framework.____
>>>>> 
>>>>>                                          * rfc8924 lists
>>>>>                                            requirements in S4, but
>>>>>                                            this document mentions
>>>>>                                            them in
>>>>>                                            passing. Instead, as per
>>>>>                                            the Abstract above, this
>>>>>                                            document creates new
>>>>>                                            requirements and based
>>>>>                                            on them creates a new
>>>>>                                            OAM protocol.____
>>>>> 
>>>>>                                    GIM>> We've followed the
>>>>>                                    requirements listed in RFC 8924
>>>>>                                    and used them when designing SFC
>>>>>                                    Echo Request/Reply. SFC Echo
>>>>>                                    Request/Reply addresses the
>>>>>                                    essential requirements in
>>>>>                                    Section 4 of RFC 8924.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: That’s an issue, those are not
>>>>>                                requirements for a new protocol.
>>>>>                                Neither for a single protocol to
>>>>>                                perform all functions.____
>>>>>                                ____
>>>>>                                CMP: Specifically, RFC 8924 says:____
>>>>>                                ____
>>>>> 
>>>>>                                CMP:   “7.  Candidate SFC OAM Tools”____
>>>>> 
>>>>>                                CMP: Why were candidates descarted?
>>>>>                                When it is shown how they can
>>>>>                                address some of the functions.____
>>>>>                                ____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                          * rfc8924 lists candidate
>>>>>                                            SFC OAM tools, but this
>>>>>                                            document does not
>>>>>                                            consider them. Or
>>>>>                                            compare requirements to
>>>>>                                            options. Perhaps I could
>>>>>                                            be pointed to the
>>>>>                                            discussion on the list?____
>>>>> 
>>>>>                                    GIM>> RFC 8924 already provides
>>>>>                                    the analysis and pointed out
>>>>>                                    gaps in listed protocols. RFC
>>>>>                                    8924 has concluded that none of
>>>>>                                    the available tools complies
>>>>>                                    with the requirements. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I do not see that conclusion in
>>>>>                                RFC 8924, perhaps you can quote /
>>>>>                                copy/paste the relevant text. The
>>>>>                                specific text that includes a
>>>>>                                conclusion. And specific text that
>>>>>                                says that none of the tools comply
>>>>>                                with the requirements.____
>>>>>                                ____
>>>>>                                CMP: In any case, there is also no
>>>>>                                implication that creating a new
>>>>>                                protocol for all requirements and
>>>>>                                ignoring the analysis of existing
>>>>>                                protocols that can be used or
>>>>>                                extended is in the best interest of
>>>>>                                SFC’s OAM.____
>>>>>                                ____
>>>>>                                CMP: Additionally, I did not see the
>>>>>                                discussion on the list of this
>>>>>                                comparison (since it does not exist
>>>>>                                in the draft).____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Additionally, I wonder: Why
>>>>>                                        the file name
>>>>>                                        “sfc-multi-layer-oam”?____
>>>>> 
>>>>>                                    GIM>> It is historical. ____
>>>>> 
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                           Active OAM tools,____
>>>>> 
>>>>>                                           conformant to the
>>>>>                                        requirements listed in
>>>>>                                        Section 3, improve, for____
>>>>> 
>>>>>                                           example, troubleshooting
>>>>>                                        efficiency and defect
>>>>>                                        localization in SFP____
>>>>> 
>>>>>                                           because they specifically
>>>>>                                        address the architectural
>>>>>                                        principles of____
>>>>> 
>>>>>                                           NSH.  For that purpose,
>>>>>                                        SFC Echo Request and Echo
>>>>>                                        Reply are specified____
>>>>> 
>>>>>                                           in Section 6.____
>>>>> 
>>>>>                                        ____
>>>>>                                        I do not fully follow these
>>>>>                                        cause-consequence pair of
>>>>>                                        sentences. They seem to be
>>>>>                                        foundational to the rational
>>>>>                                        of the document, is this why
>>>>>                                        a new OAM protocol is used?____
>>>>> 
>>>>>                                    GIM>> Indeed. Based on the
>>>>>                                    analysis in RFC 8924, we've
>>>>>                                    learned that none of the
>>>>>                                    available OAM tools can address
>>>>>                                    the requirements for active SFP
>>>>>                                    OAM. The SFC Echo Request/Reply
>>>>>                                    is specifically designed to
>>>>>                                    address these requirements.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: This is a very useful response.
>>>>>                                As I responded above, there’s no
>>>>>                                implication that if no existing
>>>>>                                tools address all requirements, the
>>>>>                                path is to create a brand new one
>>>>>                                ignoring the existing ones.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Specifically, I feel this
>>>>>                                        document over-reaches in
>>>>>                                        that it presumes that the
>>>>>                                        only “Active OAM” protocol
>>>>>                                        for NSH SFCs is this new
>>>>>                                        protocol, whereas some of
>>>>>                                        the existing protocols
>>>>>                                        listed in rfc8924 are also
>>>>>                                        “Active OAM”.____
>>>>> 
>>>>>                                    GIM>> I think that the document
>>>>>                                    is positioned not as a general
>>>>>                                    active OAM protocol but as one
>>>>>                                    of the active SFC NSH OAM
>>>>>                                    protocols.____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           This mechanism enables
>>>>>                                        on-demand Continuity Check,____
>>>>> 
>>>>>                                           Connectivity
>>>>>                                        Verification, among other
>>>>>                                        operations over SFC in____
>>>>> 
>>>>>                                           networks, addresses
>>>>>                                        functionalities discussed in
>>>>>                                        Sections 4.1, 4.2,____
>>>>> 
>>>>>                                           and 4.3 of [RFC8924].____
>>>>> 
>>>>>                                        ____
>>>>>                                        This could be well the case
>>>>>                                        — however many others
>>>>>                                        (including existing)
>>>>>                                        mechanisms also enable in
>>>>>                                        these broad terms all the
>>>>>                                        connectivity+continuity+trace functions.____
>>>>> 
>>>>>                                    GIM>> We are not questioning
>>>>>                                    that there are other solutions.
>>>>>                                    But these mechanisms are not
>>>>>                                    supported by specifications that
>>>>>                                    ensure independent interoperable
>>>>>                                    implementations. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Can you please point to
>>>>>                                independent interoperable
>>>>>                                implementations
>>>>>                                of draft-ietf-sfc-multi-layer-oam?____
>>>>>                                ____
>>>>>                                CMP: Part of my point is that any
>>>>>                                partial solution can be extended
>>>>>                                interoperably.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        At the same time, this
>>>>>                                        mechanisms is very complex. ____
>>>>>                                        I would like to see a study
>>>>>                                        of comparative benefits of
>>>>>                                        this added complexity
>>>>>                                        vis-a-vis existing
>>>>>                                        approaches that can be
>>>>>                                        extended.____
>>>>> 
>>>>>                                    GIM>> In the face of absence of
>>>>>                                    sufficient and up to date
>>>>>                                    documentation describing
>>>>>                                    proprietary solutions, I don't
>>>>>                                    see that any comparison can be
>>>>>                                    comprehensive.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I am not sure if you are
>>>>>                                answering a different question, but
>>>>>                                there’s no reference to any
>>>>>                                proprietary solutions.____
>>>>>                                ____
>>>>>                                CMP: ICMP, BFD, iOAM,
>>>>>                                SFC-Tracceroute, all documented in
>>>>>                                I-Ds and with open source
>>>>>                                implementations.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                           The ingress may be____
>>>>> 
>>>>>                                           capable of recovering
>>>>>                                        from the failure, e.g.,
>>>>>                                        using redundant SFC____
>>>>> 
>>>>>                                           elements.  Thus, it is
>>>>>                                        beneficial for the egress to
>>>>>                                        signal the new____
>>>>> 
>>>>>                                           defect state to the
>>>>>                                        ingress, which in this
>>>>>                                        example is the Classifier.____
>>>>> 
>>>>>                                           Hence the following
>>>>>                                        requirement:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                              REQ#3: SFC OAM MUST
>>>>>                                        support Remote Defect
>>>>>                                        Indication notification____
>>>>> 
>>>>>                                              by the egress to the
>>>>>                                        ingress.____
>>>>> 
>>>>>                                        ____
>>>>>                                        I see a gap between “it is
>>>>>                                        beneficial” and “MUST”. What
>>>>>                                        is "Remote Defect
>>>>>                                        Indication” in the context
>>>>>                                        of SFC OAM since it is not
>>>>>                                        in the OAM framework? Is
>>>>>                                        this "Remote Defect
>>>>>                                        Indication” the only way to
>>>>>                                        achieve the rerouting or
>>>>>                                        redundancy triggering?____
>>>>> 
>>>>>                                    GIM>> That is one of possible
>>>>>                                    solutions. Other mechanisms may
>>>>>                                    conform to the requirement using
>>>>>                                    different approach. ____
>>>>> 
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                        4.  Active OAM
>>>>>                                        Identification in the NSH____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           The O bit in the NSH is
>>>>>                                        defined in [RFC8300] as
>>>>>                                        follows:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                              O bit: Setting this
>>>>>                                        bit indicates an OAM packet.____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           This document updates
>>>>>                                        that definition as follows:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                              O bit: Setting this
>>>>>                                        bit indicates an OAM command
>>>>>                                        and/or data in____
>>>>> 
>>>>>                                              the NSH Context Header
>>>>>                                        or packet payload.____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           Active SFC OAM is defined
>>>>>                                        as a combination of OAM
>>>>>                                        commands and/or____
>>>>> 
>>>>>                                           data included in a
>>>>>                                        message that immediately
>>>>>                                        follows the NSH.  To____
>>>>> 
>>>>>                                           identify the active OAM
>>>>>                                        message, the "Next Protocol"
>>>>>                                        field MUST be____
>>>>> 
>>>>>                                           set to Active SFC OAM
>>>>>                                        (TBA1) (Section 9.1). ____
>>>>> 
>>>>>                                        ____
>>>>>                                        This is an example of
>>>>>                                        over-reach. A “Next
>>>>>                                        Protocol” pointing to IPv4,
>>>>>                                        in turn pointing to ICMP, in
>>>>>                                        turn pointing to Echo is
>>>>>                                        already one example of
>>>>>                                        “Active SFC OAM”. I wonder
>>>>>                                        if this new protocol might
>>>>>                                        be best served by choosing a
>>>>>                                        name that is not so generic?
>>>>>                                        It could be called “One of
>>>>>                                        many active SFC OAM
>>>>>                                        protocols” :-) ____
>>>>> 
>>>>>                                    GIM>> Will clarify that
>>>>>                                    throughout the document "active
>>>>>                                    OAM" and "active SFC OAM" refers
>>>>>                                    to specially constructed packets
>>>>>                                    that immediately follow the SFC
>>>>>                                    Active OAM Header (Figure 2).____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: The “SFC Active OAM Header” is
>>>>>                                therefore not part of the “active
>>>>>                                SFC OAM” packet?____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Otherwise, the “MUST” in the
>>>>>                                        last sentence seems to not
>>>>>                                        follow.____
>>>>>                                        ____
>>>>> 
>>>>>                                           The rules for____
>>>>> 
>>>>>                                           interpreting the values
>>>>>                                        of the O bit and the "Next
>>>>>                                        Protocol" field____
>>>>> 
>>>>>                                           are as follows:____
>>>>> 
>>>>>                                        ____
>>>>>                                        I am extremely concerned
>>>>>                                        about this attempted
>>>>>                                        re-definition (of the O-bit
>>>>>                                        and Protocol fields). On
>>>>>                                        several fronts as explained
>>>>>                                        below. During RFC8300 the WG
>>>>>                                        evaluated these and provided
>>>>>                                        a solution already.____
>>>>>                                        ____
>>>>> 
>>>>>                                           *  O bit set and the
>>>>>                                        "Next Protocol" value does
>>>>>                                        not match one of____
>>>>> 
>>>>>                                              identifying active or
>>>>>                                        hybrid OAM protocols (per
>>>>>                                        classification____
>>>>> 
>>>>>                                              defined in [RFC7799]),
>>>>>                                        e.g., defined in Section 9.1
>>>>>                                        Active SFC OAM____
>>>>> 
>>>>>                                              (TBA1).____
>>>>> 
>>>>>                                        This potentially breaks the
>>>>>                                        concept of nodes not
>>>>>                                        understanding OAM (i.e,.
>>>>>                                        Partial deployment of a new
>>>>>                                        protocol)____
>>>>> 
>>>>>                                    GIM>> Can you clarify what do
>>>>>                                    you mean by "nodes not
>>>>>                                    understanding OAM"? Partial
>>>>>                                    deployment is, in my opinion, an
>>>>>                                    operational issue. An operator
>>>>>                                    plans deployments of new
>>>>>                                    releases according to new
>>>>>                                    features and their intended use.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Apologies, I meant not
>>>>>                                s/understanding/parsing/.____
>>>>>                                ____
>>>>>                                CMP: I agree it is an operational
>>>>>                                issue — an issue of operations. Like
>>>>>                                the “O” in “OAM”. Should Operational
>>>>>                                Considerations be included as well?____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                 - a Fixed-Length
>>>>>                                        Context Header or
>>>>>                                        Variable-Length Context____
>>>>> 
>>>>>                                                 Header(s) contain
>>>>>                                        an OAM command or data.____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                 - the "Next
>>>>>                                        Protocol" field determines
>>>>>                                        the type of payload.____
>>>>> 
>>>>>                                        The semantic of Context
>>>>>                                        Headers is outside this
>>>>>                                        definition. For example the
>>>>>                                        types in MD Type 2 define
>>>>>                                        the variable headers. ____
>>>>>                                        ____
>>>>>                                        This potentially breaks also
>>>>>                                        OAM, since things like ECMP
>>>>>                                        can be encoded in context
>>>>>                                        headers that the OAM needs.
>>>>>                                        (e.g., "Flow ID”
>>>>>                                        from draft-ietf-sfc-nsh-tlv).____
>>>>> 
>>>>>                                    GIM>> As I understand it, MD
>>>>>                                    Type 2 Flow ID TLV is
>>>>>                                    recommended to identify a flow
>>>>>                                    in SFC NSH. The document makes
>>>>>                                    the use of this method. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: How?____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Further, is this describing
>>>>>                                        a Hybrid OAM use?____
>>>>> 
>>>>>                                    GIM>> No, the document does not
>>>>>                                    describe the use of hybrid OAM
>>>>>                                    (per RFC 7799). ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           *  O bit set and the
>>>>>                                        "Next Protocol" value
>>>>>                                        matches one of identifying____
>>>>> 
>>>>>                                              active or hybrid OAM
>>>>>                                        protocols:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                 - the payload that
>>>>>                                        immediately follows the NSH
>>>>>                                        MUST contain an____
>>>>> 
>>>>>                                                 OAM command or data.____
>>>>> 
>>>>>                                        This is also unclear — what
>>>>>                                        is an OAM command or data?
>>>>>                                        If the O-bit is set, it is
>>>>>                                        an OAM packet.____
>>>>> 
>>>>>                                    GIM>> What is an OAM packet? Is
>>>>>                                    an SFC NSH packet with IOAM an
>>>>>                                    OAM packet or not? If an SFC NSH
>>>>>                                    packet is part of flow under the
>>>>>                                    Alternate Marking, is it an OAM
>>>>>                                    packet because the Alternate
>>>>>                                    Marking method is an example of
>>>>>                                    the hybrid OAM? ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: This reads like not answering
>>>>>                                by asking questions. ____
>>>>>                                ____
>>>>>                                CMP: A user packet with marking,
>>>>>                                implicitly or explicitly, is not an
>>>>>                                OAM packet.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           *  O bit is clear:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                 - no OAM in a
>>>>>                                        Fixed-Length Context Header
>>>>>                                        or Variable-Length____
>>>>> 
>>>>>                                                 Context Header(s).____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                 - the payload
>>>>>                                        determined by the "Next
>>>>>                                        Protocol" field MUST be____
>>>>> 
>>>>>                                                 present.____
>>>>> 
>>>>>                                        It is unclear the rational
>>>>>                                        for this.____
>>>>> 
>>>>>                                    GIM>> Can you please clarify
>>>>>                                    your interpretation, so we can
>>>>>                                    look for ways to improve the
>>>>>                                    text?____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Same as above. It is unclear
>>>>>                                why these rules. It is not a matter
>>>>>                                of interpretation.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           *  O bit is clear, and
>>>>>                                        the "Next Protocol" field
>>>>>                                        identifies active or____
>>>>> 
>>>>>                                              hybrid OAM protocol
>>>>>                                        MUST be identified and
>>>>>                                        reported as an____
>>>>> 
>>>>>                                              erroneous
>>>>>                                        combination.  An
>>>>>                                        implementation MAY have
>>>>>                                        control to____
>>>>> 
>>>>>                                              enable processing of
>>>>>                                        the OAM payload.____
>>>>> 
>>>>>                                        This seems to break the
>>>>>                                        existing usage
>>>>>                                        in draft-ietf-sfc-ioam-nsh.
>>>>>                                        Section 4.2
>>>>>                                        of draft-ietf-sfc-ioam-nsh
>>>>>                                        says clearly:____
>>>>> 
>>>>>                                    GIM>> I don't see any problem.
>>>>>                                    In fact, both definitions are in
>>>>>                                    sync. According to
>>>>>                                    draft-ietf-sfc-ioam-nsh if the
>>>>>                                    Next Protocol field identifies a
>>>>>                                    use data payload, e.g., IPv6,
>>>>>                                    then O bit MUST NOT be set. If
>>>>>                                    the Next Protocol is set to
>>>>>                                    IOAM, then the O-bit MUST be
>>>>>                                    set.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Sorry, but you do not seem to
>>>>>                                be actually reading
>>>>>                                draft-ietf-sfc-ioam-nsh. Please
>>>>>                                refer to:____
>>>>>                                ____
>>>>>                                CMP:
>>>>>                                https://datatracker.ietf.org/doc/html/draft-ietf-sfc-ioam-nsh#section-4.2
>>>>>                                <https://datatracker.ietf.org/doc/html/draft-ietf-sfc-ioam-nsh#section-4.2>____
>>>>>                                ____
>>>>>                                CMP: 4.2.  IOAM and the use of the
>>>>>                                NSH O-bit____
>>>>>                                   [RFC8300] defines an "O bit" for
>>>>>                                OAM packets.  Per [RFC8300] the O____
>>>>>                                   bit must be set for OAM packets
>>>>>                                and must not be set for non-OAM____
>>>>>                                   packets.  Packets with IOAM data
>>>>>                                included MUST follow this____
>>>>>                                   definition, i.e. the O bit MUST
>>>>>                                NOT be set for regular customer____
>>>>>                                   traffic which also carries IOAM
>>>>>                                data and the O bit MUST be set for____
>>>>>                                   OAM packets which carry only IOAM
>>>>>                                data without any regular data____
>>>>>                                   payload.____
>>>>> 
>>>>>                                CMP: Please note the “MUST NOT” in
>>>>>                                the paragraph immediately above.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                    We agree in how O-bit works in
>>>>>                                    presence of IOAM that
>>>>>                                    accompanies user data and
>>>>>                                    without it.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I do not see that agreement.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        4.2.  IOAM and the use of
>>>>>                                        the NSH O-bit____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           [RFC8300] defines an "O
>>>>>                                        bit" for OAM packets.  Per
>>>>>                                        [RFC8300] the O____
>>>>> 
>>>>>                                           bit must be set for OAM
>>>>>                                        packets and must not be set
>>>>>                                        for non-OAM____
>>>>> 
>>>>>                                           packets.  Packets with
>>>>>                                        IOAM data included MUST
>>>>>                                        follow this____
>>>>> 
>>>>>                                           definition, i.e. the O
>>>>>                                        bit MUST NOT be set for
>>>>>                                        regular customer____
>>>>> 
>>>>>                                           traffic which also
>>>>>                                        carries IOAM data and the O
>>>>>                                        bit MUST be set for____
>>>>> 
>>>>>                                           OAM packets which carry
>>>>>                                        only IOAM data without any
>>>>>                                        regular data____
>>>>> 
>>>>>                                           payload.____
>>>>> 
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                        5.  Active SFC OAM Header____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           As demonstrated in
>>>>>                                        Section 4 [RFC8924] and
>>>>>                                        Section 3 of this____
>>>>> 
>>>>>                                           document, SFC OAM is
>>>>>                                        required to perform multiple
>>>>>                                        tasks.  Several____
>>>>> 
>>>>>                                           active OAM protocols
>>>>>                                        could be used to address all
>>>>>                                        the requirements.____
>>>>> 
>>>>>                                           When IP/UDP encapsulation
>>>>>                                        of an SFC OAM control
>>>>>                                        message is used,____
>>>>> 
>>>>>                                           protocols can be
>>>>>                                        demultiplexed using the
>>>>>                                        destination UDP port number.____
>>>>> 
>>>>>                                           But extra IP/UDP headers,
>>>>>                                        especially in an IPv6
>>>>>                                        network, add____
>>>>> 
>>>>>                                           noticeable overhead.                                         This document defines Active
>>>>>                                        OAM Header____
>>>>> 
>>>>>                                           (Figure 2) to demultiplex
>>>>>                                        active OAM protocols on an SFC.____
>>>>> 
>>>>>                                        ____
>>>>>                                        Does this paragraph imply
>>>>>                                        that the main reason for
>>>>>                                        this protocol is this
>>>>>                                        perceived overhead? If so,
>>>>>                                        experience seems to show
>>>>>                                        that in practice IP-encaped
>>>>>                                        OAM works fine (as e.g., for
>>>>>                                        LSP Ping). ____
>>>>> 
>>>>>                                    GIM>> Isn't IP/UDP
>>>>>                                    encapsulation, and IPv6 in
>>>>>                                    particular, is a larger
>>>>>                                    overhead? ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I am sorry Greg to call this
>>>>>                                out, but you are choosing again to
>>>>>                                not answer the question and instead
>>>>>                                ask another one.____
>>>>>                                ____
>>>>>                                CMP: I am happy to answer: it is
>>>>>                                larger. It also does not matter. And
>>>>>                                further it is proven to work in LSP
>>>>>                                Ping.____
>>>>>                                ____
>>>>>                                CMP: My question again: is the whole
>>>>>                                purpose of this new protocol to be
>>>>>                                overhead efficient? I am sure there
>>>>>                                are ways of encasulating that are
>>>>>                                more overhead-efficient
>>>>>                                than draft-ietf-sfc-multi-layer-oam.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Alternatively, “Next
>>>>>                                        Protocols” could be defined
>>>>>                                        for “raw” existing
>>>>>                                        protocols.____
>>>>>                                        ____
>>>>> 
>>>>>                                              Msg Type - six bits
>>>>>                                        long field identifies OAM
>>>>>                                        protocol, e.g., Echo____
>>>>> 
>>>>>                                              Request/Reply or
>>>>>                                        Bidirectional Forwarding
>>>>>                                        Detection.____
>>>>> 
>>>>>                                        ____
>>>>>                                        Why does BFD get
>>>>>                                        encapsulated in this new
>>>>>                                        protocol, as opposed to
>>>>>                                        using a “Next Protocol” for
>>>>>                                        it? That looks like
>>>>>                                        unnecessary overhead and
>>>>>                                        indirection.____
>>>>> 
>>>>>                                    GIM>> Are you proposing
>>>>>                                    assigning different Next
>>>>>                                    Protocol values for every
>>>>>                                    possible active OAM protocol? ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I am not proposing anything. I
>>>>>                                am simply asking a question.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                              Flags - eight bits
>>>>>                                        long field carries bit flags
>>>>>                                        that define____
>>>>> 
>>>>>                                              optional capability
>>>>>                                        and thus processing of the
>>>>>                                        SFC active OAM____
>>>>> 
>>>>>                                              control packet, e.g.,
>>>>>                                        optional timestamping. ____
>>>>> 
>>>>>                                        Does this timestamp conflict
>>>>>                                        with context header
>>>>>                                        timestamps? E.g., rfc8592
>>>>>                                        or draft-mymb-sfc-nsh-allocation-timestamp.____
>>>>> 
>>>>>                                    GIM>> What do you see as a
>>>>>                                    potential conflict? ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Two timestamps in different
>>>>>                                parts of a packet.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        6.  Echo Request/Echo Reply
>>>>>                                        for SFC____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           Echo Request/Reply is a
>>>>>                                        well-known active OAM
>>>>>                                        mechanism extensively____
>>>>> 
>>>>>                                           used to verify a path's
>>>>>                                        continuity, detect
>>>>>                                        inconsistencies between a____
>>>>> 
>>>>>                                           state in control and the
>>>>>                                        data planes, and localize
>>>>>                                        defects in the____
>>>>> 
>>>>>                                           data plane.  ICMP
>>>>>                                        ([RFC0792] for IPv4 and
>>>>>                                        [RFC4443] for IPv6____
>>>>> 
>>>>>                                           networks, respectively)
>>>>>                                        and [RFC8029] are examples
>>>>>                                        of broadly used____
>>>>> 
>>>>>                                           active OAM protocols
>>>>>                                        based on the Echo
>>>>>                                        Request/Reply principle.  The____
>>>>> 
>>>>>                                           SFC Echo Request/Reply
>>>>>                                        defined in this document
>>>>>                                        addresses several____
>>>>> 
>>>>>                                           requirements listed in
>>>>>                                        Section 3.  Specifically, it
>>>>>                                        can be used to____
>>>>> 
>>>>>                                           check the continuity of
>>>>>                                        an SFP, trace an SFP, or
>>>>>                                        localize the failure____
>>>>> 
>>>>>                                           within an SFP.  The SFC
>>>>>                                        Echo Request/Reply control
>>>>>                                        message format is____
>>>>> 
>>>>>                                           presented in Figure 3.____
>>>>> 
>>>>>                                        ____
>>>>>                                        This seems to be an
>>>>>                                        important paragraph — would
>>>>>                                        be useful to also understand
>>>>>                                        how other existing and
>>>>>                                        broadly used protocols
>>>>>                                        cannot fulfill requirements.____
>>>>> 
>>>>>                                    GIM>> RFC 8924 already provided
>>>>>                                    a comprehensive analysis and
>>>>>                                    concluded that none of the
>>>>>                                    available tools can fully
>>>>>                                    conform to the requirements
>>>>>                                    listed in Section 4. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: As per above, I do not see that
>>>>>                                conclusion.____
>>>>>                                ____
>>>>>                                CMP: And frankly even if that was
>>>>>                                the case, there’s no implication
>>>>>                                that using the existing pieces is
>>>>>                                not sufficient, or that it is not
>>>>>                                easier to extend the candidate
>>>>>                                protocols.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                              Length -
>>>>>                                        two-octet-long field equal
>>>>>                                        to the Value field's length in____
>>>>> 
>>>>>                                             octets.____
>>>>> 
>>>>>                                        ____
>>>>>                                        There are several nested
>>>>>                                        lengths defined in this
>>>>>                                        document — would be useful
>>>>>                                        to analyze that they do not
>>>>>                                        result in issues such as
>>>>>                                        piggybacking unaccounted
>>>>>                                        data.____
>>>>> 
>>>>>                                    GIM>> Do you see any scenario
>>>>>                                    when that might be the case? ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        6.3.1.  Source TLV____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           Responder to the SFC Echo
>>>>>                                        Request encapsulates the SFC
>>>>>                                        Echo Reply____
>>>>> 
>>>>>                                           message in IP/UDP packet
>>>>>                                        if the Reply mode is "Reply
>>>>>                                        via an IPv4/IPv6____
>>>>> 
>>>>>                                           UDP Packet".  Because the
>>>>>                                        NSH does not identify the
>>>>>                                        ingress node that____
>>>>> 
>>>>>                                           generated the Echo
>>>>>                                        Request, the source ID MUST
>>>>>                                        be included in the____
>>>>> 
>>>>>                                           message and used as the
>>>>>                                        IP destination address and
>>>>>                                        destination UDP____
>>>>> 
>>>>>                                           port number of the SFC
>>>>>                                        Echo Reply.  The sender of
>>>>>                                        the SFC Echo____
>>>>> 
>>>>>                                           Request MUST include an
>>>>>                                        SFC Source TLV (Figure 5).____
>>>>> 
>>>>>                                        ____
>>>>>                                        This seems to negate the
>>>>>                                        benefit of less overhead, if
>>>>>                                        the IP/UDP fields are
>>>>>                                        embedded as OAM TLVs.____
>>>>> 
>>>>>                                    GIM>> Only the Source ID is
>>>>>                                    required, not the whole set of
>>>>>                                    IP and UDP headers. ____
>>>>> 
>>>>>                                        ____
>>>>>                                        This also seems to be a bit
>>>>>                                        of an invitation for an
>>>>>                                        attack.____
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                        6.4.1.  Errored TLVs TLV____
>>>>> 
>>>>>                                        ____
>>>>>                                        I wonder at this point if it
>>>>>                                        is easier to use LSP Ping
>>>>>                                        directly instead of
>>>>>                                        re-define it.____
>>>>> 
>>>>>                                    GIM>> If someone wants to
>>>>>                                    explore that option, of course. ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        6.5.1.  SFC Reply Path TLV____
>>>>> 
>>>>>                                        …____
>>>>> 
>>>>>                                           *  Service Index: the
>>>>>                                        value for the Service Index
>>>>>                                        field in the NSH of____
>>>>> 
>>>>>                                              the SFC Echo Reply
>>>>>                                        message.____
>>>>> 
>>>>>                                        How is the service index in
>>>>>                                        a reply constructed?____
>>>>> 
>>>>>                                    GIM>> It is provided by the
>>>>>                                    sender of the SFC Echo Request. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Does this mean it skips hops?
>>>>>                                Apologies I do not understand.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>>                                        ____
>>>>> 
>>>>>                                        6.5.3.  SFC Echo Reply
>>>>>                                        Reception____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           An SFF SHOULD NOT accept
>>>>>                                        SFC Echo Reply unless the
>>>>>                                        received message____
>>>>> 
>>>>>                                           passes the following checks:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           *  the received SFC Echo
>>>>>                                        Reply is well-formed;____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           *  it has an outstanding
>>>>>                                        SFC Echo Request sent from
>>>>>                                        the UDP port that____
>>>>> 
>>>>>                                              matches destination
>>>>>                                        UDP port number of the
>>>>>                                        received packet;____
>>>>> 
>>>>>                                        ____
>>>>>                                        Is the demultiplexing based
>>>>>                                        on UDP, OAM handle, or
>>>>>                                        combination?____
>>>>> 
>>>>>                                    GIM>> The values of the Sender's
>>>>>                                    Handle and  Sequence Number
>>>>>                                    fields can be used.____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: I understand several values can
>>>>>                                be used.____
>>>>>                                CMP: Which one is actually used?____
>>>>>                                CMP: If the Handles and sequences
>>>>>                                match but not the port?____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        6.6.  Verification of the
>>>>>                                        SFP Consistency____
>>>>> 
>>>>>                                           *  Collect information of
>>>>>                                        the traversed by the CVReq
>>>>>                                        packet SFs and____
>>>>> 
>>>>>                                              send it to the ingress
>>>>>                                        SFF as CVRep packet over IP
>>>>>                                        network;____
>>>>> 
>>>>>                                        ____
>>>>>                                        What if NSH is not over IP?____
>>>>> 
>>>>>                                    GIM>> Then the operator will
>>>>>                                    specify another method using the
>>>>>                                    Reply mode. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Sorry that does not answer my
>>>>>                                question. The text in question is
>>>>>                                not contextual to a specified reply
>>>>>                                mode.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           SF Type: Two octets long
>>>>>                                        field.  It is defined in
>>>>>                                        [RFC9015] and____
>>>>> 
>>>>>                                           indicates the type of SF,
>>>>>                                        e.g., Firewall, Deep Packet
>>>>>                                        Inspection, WAN____
>>>>> 
>>>>>                                           optimization controller,
>>>>>                                        etc.____
>>>>> 
>>>>>                                        ____
>>>>>                                        Is RFC 9015 a hard
>>>>>                                        dependency to implement this
>>>>>                                        OAM? ____
>>>>> 
>>>>>                                    GIM>> RFC 9015 established the
>>>>>                                    IANA registry of SF Type and any
>>>>>                                    new SF types must be registered.____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           IANA is requested to
>>>>>                                        assign a new type from the
>>>>>                                        SFC Active OAM____
>>>>> 
>>>>>                                           Message Type sub-registry
>>>>>                                        as follows:____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                                                                         +=======+=============================+===============+____
>>>>> 
>>>>>                                                  | Value |                                                Description         |
>>>>>                                        Reference     |____
>>>>> 
>>>>>                                                                                         +=======+=============================+===============+____
>>>>> 
>>>>>                                                  | TBA2  | SFC Echo
>>>>>                                        Request/Echo Reply | This
>>>>>                                        document |____
>>>>> 
>>>>>                                                                                         +-------+-----------------------------+---------------+____
>>>>> 
>>>>>                                        ____
>>>>>                                        Is there a single value for
>>>>>                                        both Request and Reply?____
>>>>> 
>>>>>                                    GIM>> Yes, it is a single value.
>>>>>                                    Echo Request and Echo Reply are
>>>>>                                    identified in the Message Type
>>>>>                                    field (Figure 3). ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Is this document defining a
>>>>>                                full 64k space for a single value?
>>>>>                                If so it appears to be wasteful.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        9.2.1.  Version in the
>>>>>                                        Active SFC OAM Header____
>>>>> 
>>>>>                                        9.3.1.  SFC Echo
>>>>>                                        Request/Reply Version____
>>>>> 
>>>>>                                        ____
>>>>>                                        There seems to be a version
>>>>>                                        for the OAM and a version
>>>>>                                        for the msg type. Is this
>>>>>                                        correct? Are they
>>>>>                                        hierarchical versions? Or
>>>>>                                        independent? ____
>>>>>                                        This seems to overly
>>>>>                                        complicate parsing and
>>>>>                                        compliance.____
>>>>> 
>>>>>                                    GIM>> All versions are
>>>>>                                    independent. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: This seems like an operational
>>>>>                                unnecessary complexity, in keeping a
>>>>>                                matrix of supported combination of
>>>>>                                versions. If there was an
>>>>>                                Operational Considerations section,
>>>>>                                this should be included.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        9.3.3.  SFC Echo
>>>>>                                        Request/Echo Reply Message
>>>>>                                        Types____
>>>>> 
>>>>>                                        Does this mean that there’s
>>>>>                                        a protocol number for
>>>>>                                        “Active OAM” with a protocol
>>>>>                                        number for “Request/Reply”
>>>>>                                        with a protocol number for
>>>>>                                        either request or reply?____
>>>>> 
>>>>>                                    GIM>> These are not all protocol
>>>>>                                    numbers. Only the Active OAM is
>>>>>                                    a new protocol number. Others
>>>>>                                    are message types. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Apologies I was not clear.____
>>>>>                                CMP: The “SFC Active OAM” is
>>>>>                                actually a "SFC Next Protocol”.____
>>>>>                                CMP: My intention of using “protocol
>>>>>                                number” is in a generic way. To get
>>>>>                                to some OAM function, a node needs
>>>>>                                to recursively parse 3 TLVs.
>>>>>                                Correct? This seems overly complex.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                           Values defined for the
>>>>>                                        Return Codes sub-registry
>>>>>                                        are listed in____
>>>>> 
>>>>>                                           Table 14.____
>>>>> 
>>>>>                                        ____
>>>>>                                        Various values in this table
>>>>>                                        are not defined in the
>>>>>                                        document. The procedures
>>>>>                                        seem lacking.____
>>>>> 
>>>>>                                    GIM>> Other specifications may
>>>>>                                    define additional code points in
>>>>>                                    the registry. ____
>>>>> 
>>>>>                                ____
>>>>>                                CMP: Thank you. The procedures still
>>>>>                                seem lacking.____
>>>>>                                ____
>>>>>                                CMP: Best,____
>>>>>                                ____
>>>>>                                CMP: — Carlos.____
>>>>> 
>>>>>                                ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                        9.7.  SF Identifier Types____
>>>>> 
>>>>>                                        This document seems to be
>>>>>                                        creating a space for
>>>>>                                        identifying SFs — which I
>>>>>                                        thought was mostly outside
>>>>>                                        the scope of OAM to test
>>>>>                                        SFs. ____
>>>>> 
>>>>>                                    GIM>> The registry is of SF
>>>>>                                    Identifiers, not of SF Types
>>>>>                                    (that already exists). Hope that
>>>>>                                    clarifies the issue. ____
>>>>> 
>>>>>                                        ____
>>>>>                                        Does this further imply that
>>>>>                                        there’s a new requirement to
>>>>>                                        have unique identifiers
>>>>>                                        within the domain for all
>>>>>                                        SFs?____
>>>>>                                        ____
>>>>>                                        I hope these comments and
>>>>>                                        review questions and
>>>>>                                        concerns are useful for the
>>>>>                                        WG discussion and
>>>>>                                        consideration.____
>>>>>                                        ____
>>>>>                                        Thanks,____
>>>>>                                        ____
>>>>>                                        Carlos.____
>>>>>                                        ____
>>>>> 
>>>>>                                        ____
>>>>> 
>>>>>                                            Nov 1, 2021 2:50 PM、
>>>>>                                            Joel Halpern Direct
>>>>>                                            <[e-mail]
>>>>>                                            <mailto:[e-mail]>>
>>>>>                                            のメール:____
>>>>>                                            ____
>>>>>                                            I have received a polite
>>>>>                                            request with explanation
>>>>>                                            for delay asking for
>>>>>                                            more time to read and
>>>>>                                            review the subject
>>>>>                                            document.  Given the
>>>>>                                            state of the working
>>>>>                                            group, i want to
>>>>>                                            encourage any and all
>>>>>                                            review.  So I am
>>>>>                                            extending the last call
>>>>>                                            by two additional weeks.
>>>>> 
>>>>>                                            Please read and review
>>>>>                                            the document.
>>>>>                                            Also, if you are willing
>>>>>                                            to serve as shepherd for
>>>>>                                            this, please let the
>>>>>                                            chairs know.  (Don't
>>>>>                                            worry if you have not
>>>>>                                            shepherded a document
>>>>>                                            before.  The chairs are
>>>>>                                            more than happy to help
>>>>>                                            you with the process.)
>>>>> 
>>>>>                                            Thank you,
>>>>>                                            Joel
>>>>> 
>>>>>                                            _______________________________________________
>>>>>                                            sfc mailing list
>>>>>                                            [e-mail]
>>>>>                                            <mailto:[e-mail]>
>>>>>                                            https://www.ietf.org/mailman/listinfo/sfc
>>>>>                                            <https://www.ietf.org/mailman/listinfo/sfc>____
>>>>> 
>>>>>                                ____
>>>>>                                _______________________________________________
>>>>>                                sfc mailing list
>>>>>                                [e-mail] <mailto:[e-mail]>
>>>>>                                https://www.ietf.org/mailman/listinfo/sfc
>>>>>                                <https://www.ietf.org/mailman/listinfo/sfc>____
>>>>> 
>>>>>                            --____
>>>>>                            <image001.jpg> <http://www.verizon.com/>____
>>>>>                            *Gyan Mishra*____
>>>>>                            /Network Solutions Architect /____
>>>>>                            /[e-mail]
>>>>>                            <mailto:[e-mail]>/____
>>>>> 
>>>>>                            /M 301 502-1347/____
>>>>> 
>>>>>                            ____
>>>>> 
>>>>>                        ____
>>>>> 
>>>>>                    --____
>>>>>                    <image001.jpg> <http://www.verizon.com/>____
>>>>>                    *Gyan Mishra*____
>>>>>                    /Network Solutions Architect /____
>>>>>                    /[e-mail]
>>>>>                    <mailto:[e-mail]>/____
>>>>> 
>>>>>                    /M 301 502-1347/
>>>>> 
>>>> 
>>> 
>>> <Diff_ draft-ietf-sfc-multi-layer-oam-17.txt - draft-ietf-sfc-multi-layer-oam-18.txt.html>