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

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

For this usage https://datatracker.ietf.org/doc/html/rfc8924#section-7.1, the O-bit should be set. For any “vanilla” ICMP in traffic is not.

On Dec 20, 2021, at 8:07 PM, Joel Halpern Direct <[e-mail]<mailto:[e-mail]>> wrote:

from what I read, the example you provided was of an underlying ICMP Echo packet.
As I understood your email, you want SFC to mark that as OAM in the NSH header.
I would not have expected that behavior from the existing texts.

As such, whichever way we want it to work, we would seem to need to clarify our collective expectation.

More generally, I assumed the O bit of the SFC NSH header was concerned with OAM related to SFC.  I think, although I could be wrong, that you read it more generally.  Again, if different folks read it differently, we benefit from clarity.

Yours,
Joel

On 12/20/2021 8:01 PM, Carlos Pignataro (cpignata) wrote:
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]<mailto:[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]> <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]> <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]>
   <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]> <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]>
       <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]>
       <mailto:cpignata=[e-mail]>>
       *Sent:*Tuesday, 23 November 2021 15:44
       *To:*Frank Brockners (fbrockne) <[e-mail]<mailto:[e-mail]>
       <mailto:[e-mail]>>
       *Cc:*Greg Mirsky <[e-mail]<mailto:[e-mail]>
       <mailto:[e-mail]>>; Gyan Mishra
       <[e-mail]<mailto:[e-mail]> <mailto:[e-mail]>>;
       James N Guichard <[e-mail]<mailto:[e-mail]>
       <mailto:[e-mail]>>;[e-mail]<mailto:[e-mail]>
       <mailto:[e-mail]>; Joel Halpern Direct
       <[e-mail]<mailto:[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]>
           <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]>
           <mailto:[e-mail]>>
           *Sent:*Monday, 22 November 2021 23:16
           *To:*Frank Brockners (fbrockne) <[e-mail]<mailto:[e-mail]>
           <mailto:[e-mail]>>
           *Cc:*Carlos Pignataro (cpignata)
           <cpignata=[e-mail]<mailto:cpignata=[e-mail]>
           <mailto:cpignata=[e-mail]>>; Gyan
           Mishra <[e-mail]<mailto:[e-mail]>
           <mailto:[e-mail]>>; James N Guichard
           <[e-mail]<mailto:[e-mail]>
           <mailto:[e-mail]>>;[e-mail]<mailto:[e-mail]>
           <mailto:[e-mail]>; Joel Halpern Direct
           <[e-mail]<mailto:[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]>
           <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]>
               <mailto:[e-mail]>>*On Behalf Of*Carlos
               Pignataro (cpignata)
               *Sent:*Monday, 22 November 2021 00:52
               *To:*Gyan Mishra <[e-mail]<mailto:[e-mail]>
               <mailto:[e-mail]>>
               *Cc:*James N Guichard
               <[e-mail]<mailto:[e-mail]>
               <mailto:[e-mail]>>; Greg
               Mirsky <[e-mail]<mailto:[e-mail]>
               <mailto:[e-mail]>>;[e-mail]<mailto:[e-mail]>
               <mailto:[e-mail]>; Joel Halpern Direct
               <[e-mail]<mailto:[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]>
                   <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]>
                   <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]>
                           <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: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]>
                                   <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]>
                                   <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]>
                                           <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

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                           --____
                           <image001.jpg> <http://www.verizon.com/>____
                           *Gyan Mishra*____
                           /Network Solutions Architect /____
                           /[e-mail]<mailto:[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]>
                   <mailto:[e-mail]>/____

                   /M 301 502-1347/



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