Re: [Tsv-art] Tsvart telechat review of draft-ietf-sfc-oam-framework-13

"Joel M. Halpern" <jmh@joelhalpern.com> Wed, 20 May 2020 18:17 UTC

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To: "Frank Brockners (fbrockne)" <fbrockne@cisco.com>, "Nagendra Kumar Nainar (naikumar)" <naikumar@cisco.com>, "tsv-art@ietf.org" <tsv-art@ietf.org>
Cc: "sfc@ietf.org" <sfc@ietf.org>, "last-call@ietf.org" <last-call@ietf.org>, "draft-ietf-sfc-oam-framework.all@ietf.org" <draft-ietf-sfc-oam-framework.all@ietf.org>
References: <158861910132.5213.12389985411421411727@ietfa.amsl.com> <B12ACAA0-BFBC-40D6-85D2-A7E056027C68@cisco.com> <BYAPR11MB2584D5A59E020682810099EFDAB60@BYAPR11MB2584.namprd11.prod.outlook.com> <e83de1dc-1f39-6281-7687-b6dd52567685@joelhalpern.com> <BYAPR11MB258403E216B7396323CD836EDAB60@BYAPR11MB2584.namprd11.prod.outlook.com>
From: "Joel M. Halpern" <jmh@joelhalpern.com>
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Subject: Re: [Tsv-art] Tsvart telechat review of draft-ietf-sfc-oam-framework-13
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So the question now is whether the text Murray suggested suffices for 
you?  (We are still waiting to hear from Alvaro.)

Yours,
Joel

On 5/20/2020 1:41 PM, Frank Brockners (fbrockne) wrote:
> Thanks Joel. Per what I mentioned below, let's be clear that SF performance is out of scope for the doc.
> And I think this was Alvaro's point as well.
> 
> Cheers, Frank
> 
>> -----Original Message-----
>> From: Joel M. Halpern <jmh@joelhalpern.com>
>> Sent: Mittwoch, 20. Mai 2020 19:21
>> To: Frank Brockners (fbrockne) <fbrockne@cisco.com>om>; Nagendra Kumar Nainar
>> (naikumar) <naikumar@cisco.com>om>; tsv-art@ietf.org
>> Cc: sfc@ietf.org; last-call@ietf.org; draft-ietf-sfc-oam-framework.all@ietf.org
>> Subject: Re: Tsvart telechat review of draft-ietf-sfc-oam-framework-13
>>
>> Frank, regarding your comment about SF performance, I thought the document
>> was pretty clear that we consider that out of scope (c.f. the discussions with the
>> various ADs.)
>>
>> If you can see a place to add text, please propose text.
>>
>> Thank you,
>> Joel
>>
>> On 5/20/2020 1:10 PM, Frank Brockners (fbrockne) wrote:
>>> Hi Nagendra,
>>>
>>> Thanks for the detailed reply. Please see inline (..FB).
>>>
>>>> -----Original Message-----
>>>> From: Nagendra Kumar Nainar (naikumar) <naikumar@cisco.com>
>>>> Sent: Samstag, 16. Mai 2020 16:16
>>>> To: Frank Brockners (fbrockne) <fbrockne@cisco.com>om>; tsv-art@ietf.org
>>>> Cc: sfc@ietf.org; last-call@ietf.org;
>>>> draft-ietf-sfc-oam-framework.all@ietf.org
>>>> Subject: Re: Tsvart telechat review of
>>>> draft-ietf-sfc-oam-framework-13
>>>>
>>>> Hi Frank,
>>>>
>>>> Thank you for the review. Please see inline for the response..
>>>>
>>>>
>>>>       Reviewer: Frank Brockners
>>>>       Review result: Ready with Nits
>>>>
>>>>       This document has been reviewed as part of the transport area review
>> team's
>>>>       ongoing effort to review key IETF documents. These comments were
>> written
>>>>       primarily for the transport area directors, but are copied to the
>> document's
>>>>       authors and WG to allow them to address any issues raised and
>>>> also to the IETF
>>>>       discussion list for information.
>>>>
>>>>       When done at the time of IETF Last Call, the authors should consider this
>>>>       review as part of the last-call comments they receive. Please always CC
>>>>       tsv-art@ietf.org if you reply to or forward this review.
>>>>
>>>>       This document provides a reference framework for OAM for SFC.
>>>>
>>>>       Comments:
>>>>
>>>>       Section 3.1.1 SF availability: The text makes explicit reference to multiple
>>>>       instances of a SF. Consequently, it should be defined how availability of a
>> SF
>>>>       is computed/determined in case multiple instances are deployed.
>>>>
>>>> <Nagendra> This is already clarified in the section as below:
>>>>
>>>> "For cases where
>>>>      multiple instances of an SF are used to realize a given SF for the
>>>>      purpose of load sharing, SF availability can be performed by checking
>>>>      the availability of any one of those instances, or the availability
>>>>      check may be targeted at a specific instance."
>>>>
>>>> This further
>>>>       leads to the question, whether availability is always a "binary" state
>>>>       (available / not-available), or could a SF be e.g. 99% available?
>>>>
>>>> <Nagendra>The availability is measured as binary state. I am not sure
>>>> what is 99% available. If it means getting 99 responses for 100
>>>> probes sent, I think it falls under packet loss category which in turn is
>> performance measurement.
>>>
>>> ...FB: Thanks. Though I'm still not entirely following. If availability is binary and
>> I put the statements above together, what would be the availability of the
>> following setup: There is an SF that is made up of 100 instances. 99 of these
>> instances are powered down entirely. And the 1 instance that is "up" is
>> alternating between servicing requests for 10min followed by not servicing
>> requests for 10min. Would the SF be considered "available"?
>>>
>>>>
>>>> Section 3.1.2
>>>>       SF performance: What is the impact of a "multiple instance SF
>>>> deployment" on SF
>>>>       performance measurement?
>>>>
>>>> <Nagendra>I think we covered this in SF availability but not here.
>>>> Does the below updated text look better?
>>>>
>>>> OLD:
>>>> On the one hand, the performance of any specific SF can be quantified
>>>>      by measuring the loss and delay metrics of the traffic from SFF to
>>>>      the respective SF, while on the other hand, the performance can be
>>>>      measured by leveraging the loss and delay metrics from the respective
>>>>      SFs.  The latter requires SF involvement to perform the measurement
>>>>      while the former does not.
>>>>
>>>> NEW:
>>>> On the one hand, the performance of any specific SF can be quantified
>>>>      by measuring the loss and delay metrics of the traffic from SFF to
>>>>      the respective SF, while on the other hand, the performance can be
>>>>      measured by leveraging the loss and delay metrics from the respective
>>>>      SFs.  The latter requires SF involvement to perform the measurement
>>>>      while the former does not. For cases where
>>>>      multiple instances of an SF are used to realize a given SF for the
>>>>      purpose of load sharing, SF performance can be quantified by measuring
>>>>      the metrics for any one instance of SF or by measuring the metrics for
>>>>      a specific instance.
>>>>
>>>> The section only talks about loss and delay as
>>>>       performance criteria. It would be good to state that other
>>>> performance criteria
>>>>       (e.g. specific to the SF, throughput, etc.) exist.
>>>>
>>>> <Nagendra> We can add the below to Section 3.1.2:
>>>>
>>>> NEW:
>>>> "The metrics measured to quantify the performance of the SF component
>>>> is not just limited to loss and delay. Other metrics such as
>>>> throughout also exist and the choice of metrics for performance
>>>> measurement is outside the scope of this document."
>>>>
>>>> Section 3.2.1 SFC
>>>>       availability: The current definition is very focused on connectivity
>>>>       verification, i.e. it tries to answer the question: "Does my SFC transport
>>>>       packets?". IMHO we should also ask the question "Does my SFC process
>> the
>>>>       packets correctly?" - because if packets are not processed per the SFC
>>>>       definition, we might not call the SFC available.
>>>>
>>>> <Nagendra> I think this is already handled by SF availability. The
>>>> end-to-end SFC availability is verified by steering the OAM packet
>>>> over the ordered set of SFs within the SFC. This is more like daisy
>>>> chaining the availability of SFs within the SFC to determine
>>>> end-to-end SFC availability. If the derived solution verifies the SF
>>>> availability not just based on the uptime but based on the service
>>>> treatment, it also answers the question "Does my SFC process the packets
>> correctly". Let us know if there is any further clarity required.
>>>>
>>>> While 3.2.2 states that "any
>>>>       SFC-aware network device should have the ability to make performance
>>>>       measurements" a similar statement isn't found in 3.2.1. IMHO the ability
>> for
>>>>       availability checks is probably a prerequisite for performance
>> measurement.
>>>>
>>>> <Nagendra> The ability to perform end-to-end or partial SFC
>>>> availability verification is already mentioned in section 3.2.1 as below:
>>>>
>>>> " In order to perform service connectivity verification of an SFC/SFP,
>>>>      the OAM functions could be initiated from any SFC-aware network
>>>>      devices of an SFC-enabled domain for end-to-end paths, or partial
>>>>      paths terminating on a specific SF, within the SFC/SFP"
>>>>
>>>> Please let us know if you have any suggestion to improve if there is
>>>> a lack of clarity.
>>>>
>>>>       Section 3.2.2 SFC performance measurement: The section only
>>>> mentions the need
>>>>       for performance measurement. It misses the definition of what
>>>> SFC performance
>>>>       measurement is.
>>>>
>>>> <Nagendra>
>>>
>>> ...FB: Thanks for the suggested updates, which would definitively improve the
>> text. One problem about SFC performance remains though IMHO.
>>> All the text so far is focused on the connectivity within a SFC - not the service
>> itself. I.e. If you'd consider a "laundry service" - we focus a lot on how long it
>> takes to get the clothes shipped to and from the washing machine, but we don't
>> focus on how well the washing machine washes the clothes.
>>> IMHO we should either expand on the performance of the SFC and SF wrt/ the
>> service (especially given that you define a service layer in section 2) - or clearly
>> state that the framework would just focus on connectivity between SFs.
>>>
>>>
>>>>
>>>> Section 3.3. Classifier component: The section mentions the
>>>>       need for the ability to perform performance measurement of the classifier
>>>>       component. What is performance measurement of the classifier? What
>> does
>>>>       performance measurement of the classifier component comprise?
>>>>
>>>> <Nagendra>We can add the below text:
>>>>
>>>> OLD:
>>>> Any SFC-aware network device should have the ability to perform
>>>>      performance measurement of the classifier component for each SFC.
>>>>
>>>> NEW:
>>>> Any SFC-aware network device should have the ability to perform
>>>>      performance measurement of the classifier component for each SFC.
>>>>       The performance can be quantified by measuring the performance
>>>> metrics of the
>>>>        traffic from the classifier for each SFC/SFP.
>>>>
>>>> Section 3.4. /
>>>>       3.5. Availability/PM of the underlay and overlay network: It would be good
>> to
>>>>       add a sentence that states that the mechanisms for availability/PM which
>> are
>>>>       offered by the technologies used by the overlay/underlay are
>>>> used, rather than
>>>>       new methods specifically for SFC would be defined.
>>>>
>>>> <Nagendra>Yes, that makes sense. Please check the below text:
>>>>
>>>> OLD:
>>>> Any SFC-aware network device may have the ability to perform
>>>>      availability check or performance measurement of the overlay network.
>>>>
>>>> NEW:
>>>> Any SFC-aware network device may have the ability to perform
>>>>      availability check or performance measurement of the overlay network.
>> Any
>>>>      existing OAM tools and techniques can be leveraged for this purpose.
>>>>
>>>> Section 4. SFC OAM
>>>>       Functions: It would be good, if examples in section 4 could also include
>> more
>>>>       "recent" methods such as OWAMP/TWAMP (RFC4656, RFC 5357).
>>>>
>>>> <Nagendra>
>>>>
>>>> OLD:
>>>> Delay within an SFC could be measured based on the time it takes for
>>>>      a packet to traverse the SFC from the ingress SFC node to the egress
>>>>      SFF.  As SFCs are unidirectional in nature, measurement of one-way
>>>>      delay [RFC7679] is important.  In order to measure one-way delay,
>>>>      time synchronization MUST be supported by means such as NTP, PTP,
>>>>      GPS, etc.
>>>>
>>>> NEW:
>>>> Delay within an SFC could be measured based on the time it takes for
>>>>      a packet to traverse the SFC from the ingress SFC node to the egress
>>>>      SFF.  Measurement protocols such as One-way Active Measurement
>>>>       Protocol (OWAMP) [RFC4656], Two-way Active Measurement Protocol
>>>>      (TWAMP) [RFC5357] can be used to measure the characteristics. As
>>>>      SFCs are unidirectional in nature, measurement of one-way
>>>>      delay [RFC7679] is important.  In order to measure one-way delay,
>>>>      time synchronization MUST be supported by means such as NTP,
>>>> Precision Time Protocol (PTP),
>>>>      GPS, etc.
>>>>
>>>> Section 4.4.
>>>>       Performance Measurement: Focus is entirely on the PM of the
>> connectivity,
>>>>       rather than on the SF. How about covering PM for the SF as well?
>>>>
>>>> <Nagendra> I am not sure I understand what is missing. Do you have
>>>> any suggestion for the text improvement?.
>>>
>>> ...FB: See above. This would be about adding a capability to assess how well
>> the washing machine washes my laundry.
>>>
>>>>
>>>> Section 5.1
>>>>       OAM Tool Gap Analysis:
>>>>        - Not sure what "NVo3 OAM" refers to. Could that be explained
>>>> below the table
>>>>        and in section 1.2.1?
>>>>
>>>> <Nagendra> Combining this with other below queries as they appears to
>>>> be related.
>>>>
>>>> - E-OAM needs to be detailed. Is seems that CFM
>>>>        (802.1ag) and not 802.3ah is refered to here.
>>>>
>>>> <Nagendra> Per my understanding, 802.ah is 1-hop while 802.3ag can be
>>>> more than 1 hop and both uses Ethernet frames. So I think both are
>> applicable here.
>>>> My response regarding E-OAM details in this section is combined below.
>>>
>>> ...FB: Maybe I missed it - but I don't see text that refers to CFM or EFM OAM.
>> Where is this covered? IMHO we would need references to IEEE standards to
>> avoid confusion.
>>>
>>>>
>>>> - "Trace" in the "Trace" column
>>>>        need to be extended on. Is this traceroute? Paris-Traceroute?
>>>> IOAM- Loopback?
>>>>
>>>>        IPPM needs to be detailed, because IPPM is not a tool as such
>>>> but an IETF WG.
>>>>        Does this refer to OWAMP/TWAMP/etc. as defined by IPPM?
>>>>
>>>> <Nagendra> Combining the above queries.
>>>>
>>>> OLD:
>>>> There are various OAM tool sets available to perform OAM functions
>>>>      within various layers.  These OAM functions may be used to validate
>>>>      some of the underlay and overlay networks.  Tools like ping and trace
>>>>      are in existence to perform connectivity check and tracing of
>>>>      intermediate hops in a network.  These tools support different
>>>>      network types like IP, MPLS, TRILL, etc.  There is also an effort to
>>>>      extend the tool set to provide connectivity and continuity checks
>>>>      within overlay networks.  BFD is another tool which helps in
>>>>      detecting data forwarding failures.  Table 3 below is not
>>>> exhaustive
>>>>
>>>> NEW:
>>>> There are various OAM tool sets available to perform OAM functions
>>>>      within various layers.  These OAM functions may be used to validate
>>>>      some of the underlay and overlay networks.  Tools like ping and trace
>>>>      are used to perform connectivity check and tracing of
>>>>      intermediate hops in a network.  These tools are already available for
>>>>      different types of networks such as IP, MPLS, TRILL, etc.
>>>>
>>>> E-OAM offers OAM mechanisms such as an Ethernet continuity check for
>>>> Ethernet links. There is an effort around NVO3 OAM to provide
>>>> connectivity and continuity checks for networks that use NVO3.  BFD
>>>> is used for the detection of data plane forwarding failures.
>>>
>>> ...FB: Check whether NVO3 WG will indeed deliver a solution and "NVO3 OAM"
>> indeed existis. If in doubt, it might be better to avoid forward looking
>> references. Per my note above, it would be good to explicitly refer to IEEE
>> standards as opposed to introducing a new term like "E-OAM".
>>>
>>>>
>>>> The IPPM framework [RFC 2330] offers tools such as OWAMP [RFC4656]
>>>> and TWAMP [RFC5357] (collectively referred as IPPM in this section)
>>>> to measure various performance metrics. MPLS Packet Loss Measurement
>>>> (LM) and Packet Delay Measurement (DM) (collectively referred as
>>>> MPLS_PM in this section) [RFC6374] offers the ability to measure
>> performance metrics in MPLS network.
>>>>
>>>> Table 3 below is not exhaustive.
>>>>
>>>> Section 6.4.3 IOAM:
>>>>       - The section states that IOAM "may be used to perform various SFC OAM
>>>>       functions as well". It would be good to expand on this statement: E.g.
>> IOAM
>>>>       Trace-Option Type could be leveraged for SFC tracing. IOAM
>>>> Direct-Export Option
>>>>       Type could be leveraged. - How would we deal with the IOAM Active Flag
>>>>       (draft-ietf-ippm-ioam-flags-01) when used with SFC OAM?
>>>>
>>>> <Nagendra> The intention of the section is to highlight the
>>>> applicability of different OAM toolsets for OAM functions at service
>>>> layer. I am not sure if we really should try explaining all the
>>>> possible options within each tool. But I agree that it is worth
>>>> clarifying the availability of IOAM options for tracing. think we can
>>>> clarify that different IOAM Option-Types are available for OAM functions
>> such as SFC tracing. Can you check if the below looks ok?
>>>>
>>>> OLD:
>>>> [I-D.ietf-sfc-ioam-nsh] defines how In-Situ OAM data fields are
>>>>      transported using NSH header.  [I-D.ietf-sfc-proof-of-transit]
>>>>      defines a mechanism to perform proof of transit to securely verify if
>>>>      a packet traversed the relevant SFP or SFC.  While the mechanism is
>>>>      defined inband (i.e., it will be included in data packets), it may be
>>>>      used to perform various SFC OAM functions as well.
>>>>
>>>> NEW:
>>>> [I-D.ietf-sfc-ioam-nsh] defines how In-Situ OAM data fields are
>>>>      transported using NSH header.  [I-D.ietf-sfc-proof-of-transit]
>>>>      defines a mechanism to perform proof of transit to securely verify if
>>>>      a packet traversed the relevant SFP or SFC.  While the mechanism is
>>>>      defined inband (i.e., it will be included in data packets), IOAM Option-Types
>>>>     such as IOAM Trace Option-Types can also be used to perform other
>>>> SFC OAM function
>>>>     such as SFC tracing.
>>>>
>>>> - The text states
>>>>       "In-Situ OAM could be used with O bit set": Why would IOAM be used with
>> the
>>>>       overflow bit set for SFC OAM? For details on IOAM's O-bit, see section
>> 4.4.1 in
>>>>       https://tools.ietf.org/html/draft-ietf-ippm-ioam-data-09.
>>>>
>>>> <Nagendra> The O bit referred here is not the O bit in IOAM but the
>>>> one in NSH/Overlay header. To avoid any confusion, this can be updated as
>> below:
>>>>
>>>> OLD:
>>>> In-Situ OAM could be used with O bit set to perform SF availability
>>>>      and SFC availability or performance measurement.
>>>>
>>>> NEW:
>>>> In-Situ OAM could be used with O bit in the overlay header set, to
>>>> perform SF availability
>>>>      and SFC availability or performance measurement.
>>>
>>> ... FB: Ah, ok. Given that this section is about IOAM and not NSH, I'd rather
>> explicitly refer to NSH here. E.g. If SFC is realized using NSH, then the O-bit in the
>> NSH header could be used to indicated OAM traffic. You could refer to
>> https://tools.ietf.org/html/draft-ietf-sfc-ioam-nsh-03#section-4.2 explicitly.
>>>
>>>>
>>>> Section 6.4.4 SFC
>>>>       Traceroute: - This section refers to an expired draft (even calling out the
>>>>       fact that the draft has exipred), but also mentions that functionality is
>>>>       available and implemented in OpenDaylight. Consider removing the
>>>> references to
>>>>       the expired draft and rather add references to OpenDaylight
>>>> documents. - IOAM
>>>>       Loopback (see draft-ietf-ippm-ioam-flags-01) could apply SFC
>>>> Traceroute as well.
>>>>
>>>> <Nagendra>Ok. Let me check if I can find some reference for ODL.
>>>>
>>>>       Detailed set of nits that I encountered while reading through
>>>> the document ([x]
>>>>       references line number x) – hope that they are helpful in further improving
>> the
>>>>       doc:
>>>>
>>>> <Nagendra> Yes of course (.
>>>>
>>>>       [global] s/an SF/a SF/ -- and similarly SFC/SFF
>>>>
>>>> <Nagendra>Other RFCs uses "an SF/SFF". So the draft is updated
>>>> accordingly. If your suggestion is to substitute "a SF" to "an SF",  it is done (.
>>>>
>>>>       [176] "OAM Controller" not defined
>>>>
>>>> <Nagendra>We can change it as below:
>>>>
>>>> OLD:
>>>> OAM controllers are assumed to be within the same administrative
>>>>      domain as the target SFC enabled domain.
>>>>
>>>> NEW:
>>>> OAM controllers are SFC-aware network devices that are capable of
>>>> generating OAM packets. They are assumed to be within the same
>>>> administrative domain as the target SFC enabled domain.
>>>>
>>>>       [202] Why just Virtual Machines and no containers? Suggest to make
>> things
>>>>       generic and talk about virtual and physical entities.
>>>>
>>>> <Nagendra> We changed this as virtual entities.
>>>>
>>>>             This comment applies throughout the document.
>>>>       [216] Ethernet OAM: Add reference. Do you refer to physical
>>>> layer Ethernet OAM
>>>>       (802.3ah) or CFM (802.1ag)?
>>>>
>>>> <Nagendra> The response was provided in the above comment section.
>>>>
>>>> [243] s/uses the overlay network/uses the overlay
>>>>       network layer/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [246] Could we add a few examples of "various overlay network
>>>>       technologies"? For the underlay network layer several examples are listed.
>>>>
>>>> <Nagendra> Ok.
>>>>
>>>>       [248] What does "mostly transparent" mean?
>>>>
>>>> <Nagendra> The data plane elements connecting the overlay layer nodes
>>>> may not always process the overlay header.
>>>
>>> ...FB: How about we explain this in the document?
>>>
>>>>
>>>> [254] What does "tight coupling"
>>>>       between the link layer and the physical technology mean?
>>>>
>>>> <Nagendra>I am not sure I understand the nit here. Do you see any
>>>> difficulty in parsing the sentence?
>>>
>>> ...FB: Not sure what "tight coupling" means here. Could you clarify what is
>> "tight coupling" vs. "not tight coupling"?
>>>
>>>>
>>>> [255] Suggest to avoid
>>>>       terms like "popular" - popularity can change, standards stay
>>>>
>>>> <Nagendra> Ok. This is changed as "Ethernet is one such choice..."
>>>>
>>>> [256] Acronyms
>>>>       "POS" and "DWDM" are not defined
>>>>
>>>> <Nagendra> Added.
>>>>
>>>> [274] Link start/end-points don't seem to
>>>>       always align with the underlay network in the diagram
>>>>
>>>> <Nagendra> Fixed it.
>>>>
>>>> [287] s/may comprise
>>>>       of/may consist of/
>>>>
>>>> <Nagendra>We fixed it as "may comprise"..
>>>>
>>>> [288] s/but not shown/but is not shown/
>>>>
>>>> <Nagendra> We fixed this as "intermediate nodes not shown...:
>>>>
>>>> [307]
>>>>       s/devices/device/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [308] What is a "controller"?
>>>>
>>>> <Nagendra> We discussed this in the above comment section.
>>>>
>>>> [314] s/includes/include/
>>>>
>>>> <Nagendra>Done.
>>>>
>>>> [319]
>>>>       Add hSFC to list of acronyms in section 1.2.1
>>>>
>>>> <Nagendra> This is expanded in the respective section. We added it in
>>>> the acronym section as well.
>>>>
>>>> [320] Add IBN to list of acronyms
>>>>       in section 1.2.1
>>>>
>>>> <Nagendra> Ok, Done.
>>>>
>>>> [325] s/includes/include/
>>>>
>>>> <Nagendra> Done.
>>>> [359] The function/term "controller"
>>>>       requires definition.
>>>>
>>>> <Nagendra> Done, as mentioned in the above comment section.
>>>>
>>>> [383] s/?./?/
>>>>
>>>> [398] s/get the got/got/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>>    [461]
>>>>       s/devices/device/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>>    [469] Does it have to be equal cost multipath at the service
>>>>       layer, or could unequal cost multipath also be an option for load-
>> balancing?
>>>>
>>>> <Nagendra>I didn’t see any discussion specific to ECMP/UCMP in the
>>>> architecture RFC.
>>>
>>> ...FB: Hmm. I did not see that RFC7665 is only about equal cost multipath.
>>>>
>>>>    [521] Not sure whether the overlay network establishes the service plane.
>> Isn't
>>>>       it that the overlay network establishes connectivity for the SFC-related
>>>>       functions in the service plane?
>>>>
>>>> <Nagendra> The service layer is established over the overlay network
>>>> layer. I am not sure if it is right to say overlay network provides
>>>> connectivity for service layer (.
>>>
>>> ...FB: Overlay network is one component of the service layer, isn't it. So it is
>> required but not sufficient.
>>>
>>>>
>>>> [531] s/components/component/ [545] remove
>>>>       "underlay"
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [595] s/devices/device/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [600] s/action/an action/
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [601] Expand on
>>>>       "TTL or other means" (TTL also needs to be added to acronyms in 1.2.1). Is
>> this
>>>>       specific to NSH? Or specific to IPv4?
>>>>
>>>> <Nagendra> TTL is listed as well-known abbrev in https://www.rfc-
>>>> editor.org/materials/abbrev.expansion.txt and so we left it as it is.
>>>> TTL in this document refers to NSH TTL field.
>>>
>>> ...FB: Let's ensure we refer to NSH TTL in this case. Given that SFC can be done
>> with other means than NSH, implicit reference to NSH might be a problem.
>>>>
>>>>    [630] Mention that for "approximation of
>>>>       packet loss for a given SFC can be derived" to be applicable, SFC OAM
>> packets
>>>>       would need to be forwarded the same as live user traffic.
>>>>
>>>> <Nagendra> As it is intending to derive the approximate loss value, I
>>>> am not sure if we need this additional consideration that the OAM
>>>> packet would need to follow the live user traffic. Let me know if you think
>> otherwise.
>>>
>>> ...FB: IMHO we should - given that it is one potential complication.
>>>
>>>>
>>>>    [636] Is uppercase
>>>>       "MUST" applicable to an informational document? Especially given that
>>>>       RFC2119/RFC8174 is explicitly referenced by the draft.
>>>>
>>>> <Nagendra> Based on various reviewer comments, we removed the use of
>>>> any normative statement.
>>>>
>>>> [666] Add MPLS, TRILL to
>>>>       acronyms in 1.2.1
>>>>
>>>> <Nagendra> Ok. Done.
>>>>
>>>> [678] s/exhaustive/exhaustive./
>>>>
>>>> <Nagendra> Done.
>>>>
>>>> [720] Is uppercase "SHOULD" applicable to an informational document?
>>>>       Especially given that RFC2119/RFC8174 is explicitly referenced by the
>> draft.
>>>>
>>>> <Nagendra> Based on various reviewer comments, we removed the use of
>>>> any normative statement.
>>>>
>>>> [722] Is uppercase "MAY" applicable to an informational document?
>> Especially
>>>>       given that RFC2119/RFC8174 is explicitly referenced by the draft.
>>>>
>>>> <Nagendra> Based on various reviewer comments, we removed the use of
>>>> any normative statement.
>>>>
>>>> [754]
>>>>       s/packet/packets/
>>>>
>>>> [755] s/to next node/to the next node/
>>>>
>>>>    [771] How does this
>>>>       requirement align with the earlier paragraph, e.g. in case a
>>>> node sends an ICMP
>>>>       reply? It would probably make sense to scope the statement to e.g. NSH.
>>>>
>>>> <Nagendra> As mentioned in the statement, the node that initiates the
>>>> OAM packet must set the marker and so this statement is applicable
>>>> for the initiating node.
>>>>
>>>> [806]
>>>>       s/function/functions/
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [809] s/from relevant node/from the relevant node/
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [810]
>>>>       s/generate ICMP/generate an ICMP/
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [812] s/from last/from the last/
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [830]
>>>>       s/perform continuity/perform the continuity/
>>>>
>>>> <Nagendra> Done
>>>>
>>>>    [834] s/with relevant/with the
>>>>       relevant
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [835] s/perform partial SFC availability./perform a partial SFC
>>>>       availability check./
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [851] For "In-Situ OAM data fields" add a normative
>>>>       reference to draft-ietf-ippm-ioam-data
>>>>
>>>> [905] Add "CLI" to section 1.2.1
>>>>       acronyms
>>>>
>>>> <Nagendra> Done
>>>>
>>>> [920] Add a reference for NETCONF ->RFC6241
>>>>
>>>> <Nagendra> Done
>>>>
>>>> Once again, thanks a lot for the great comments.
>>>>
>>>> Regards,
>>>> Nagendra
>>>
>>> Thanks again for considering the comments in great detail. Much appreciated.
>>>
>>> Cheers, Frank
>>>>
>>>>
>>>>
>>>