Re: [Tsv-art] Tsvart telechat review of draft-ietf-sfc-oam-framework-13
Joel Halpern Direct <jmh.direct@joelhalpern.com> Fri, 22 May 2020 15:17 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> <e2b4f43f-4732-7276-f449-f62c1b97c259@joelhalpern.com> <BYAPR11MB2584A602FA170F2D85D4DC67DAB40@BYAPR11MB2584.namprd11.prod.outlook.com> <17ce4af7-054e-226c-a97f-d37a2c9480f3@joelhalpern.com> <BYAPR11MB258416CFBC777A163B892BBCDAB40@BYAPR11MB2584.namprd11.prod.outlook.com>
From: Joel Halpern Direct <jmh.direct@joelhalpern.com>
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Subject: Re: [Tsv-art] Tsvart telechat review of draft-ietf-sfc-oam-framework-13
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Thanks Frank. Both for the review, and the discussion. Yours, Joel On 5/22/2020 11:03 AM, Frank Brockners (fbrockne) wrote: > Per what I mentioned below - the below is my personal take, taking the position of a reader, who might not be aware of WG structures, WG scopes etc. Personally, I don't think that a reader of the SFC OAM framework document would expect the SFC WG to address all of the dimensions of SFC OAM, even if the document lays them out. > > That said, I do understand your concern about WG structures and scope. Looks like we (sadly) need to follow Conway's law ... > So in general terms, I'm ok with Nagendra's approach. > > Cheers, Frank > > >> -----Original Message----- >> From: Joel M. Halpern <jmh@joelhalpern.com> >> Sent: Freitag, 22. Mai 2020 16:49 >> To: Frank Brockners (fbrockne) <fbrockne@cisco.com>; Nagendra Kumar Nainar >> (naikumar) <naikumar@cisco.com>; 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 >> >> My basic concern is that if we go down the path you outline, it would suggest to >> the reader that the SFC working group expected to address the SF dimensions of >> the problem. I grant that they are real problems. But the SFC working group has >> neither the charter nor the expertise to address those problems. As far as I can >> tell, ART may have the expertise, and may not. And has shown no interest in the >> problem. So I am very reluctant to put a lot of verbiage into the RFC on SF >> monitoring. >> >> Given the above, can you live with Nagendra's text that you quote? >> >> Yours, >> Joel >> >> On 5/22/2020 5:33 AM, Frank Brockners (fbrockne) wrote: >>> Joel, >>> >>> Nagendra suggested "The task of evaluating the true availability of a >>> Service Function is a complex activity, currently having no simple, >>> unified solution. There is currently no standard means of doing so. >>> Any such mechanism would be far from a typical OAM function, so it is >>> not explored as part of the analysis in Sections 4 and 5." in the >>> related thread for discussion on availability. >>> https://mailarchive.ietf.org/arch/msg/sfc/1ZsLw6m1OeJRJfHW2TygxOyKPJk/ >>> >>> It could well be that my expectations for a framework document differ from >> that of others. So please take this as a personal perspective. >>> My expectation for a framework document is that it identifies and >>> describes the components for a solution. It can optionally also hint >>> at potential approaches to a solution (independently whether these >>> solution are already in scope of the WG or not), but does not have to >>> provide these solutions. The document does a good job at most of these >>> - but misses out on those things, where we currently don't really have >>> a solution available, which are questions like >>> * How do we define availability for a SFC at service level? How do we define >> availability for a SF? >>> * How do we define performance for a SFC at service level? How do we define >> performance for a SF? >>> Right now the document focuses on those pieces of SF/SFC availability and >> performance that are connectivity related ("Packets traverse it"). >>> >>> A potential approach could be to decompose the problem, using the structure >> the document lays out - and put this into the context of SLA definitions. >>> >>> Why can we just say for e.g. SFC performance that SFC performance is a >>> composite of >>> * link layer performance, >>> * underlay performance, >>> * overlay performance, >>> * service layer performance. >>> A SFC OAM solution needs to consider the performance measures across all >> those layers. >>> Consequently, for the performance of a SF, one needs to consider the aspects >> at each layer: >>> * link layer - Example "how well is the SF connected at e.g. Ethernet >>> layer?" -> example: Leverage ITU-T Y.1731 >>> * underlay - Example "how well is the SF connected at e.g. IP layer?" >>> -> example: Leverage OWAMP/TWAMP >>> * overlay - Example "how well is the SF connected at e.g. NSH layer?" >>> * service layer - Example "how well does the SF meet the criteria of an SLA?" >>> So e.g. 3.1.2 and 3.2.2 could explicitly expand on these aspects and state that >> apart from connectivity level measures (loss, throughput), service level criteria, >> typically defined as part of an SLA, are included in SFC performance >> characterization. IMHO this is a better approach, than either say "SF availability >> is a hard problem" (which is what Nagendra says in the above statement - and >> which is of course true) or just define the service aspects as out of scope for SFC >> OAM ("how clean are the clothes when returned from the laundry?"). >>> >>> My 2cents.. >>> >>> Cheers, Frank >>> >>> >>>> -----Original Message----- >>>> From: Joel M. Halpern <jmh@joelhalpern.com> >>>> Sent: Mittwoch, 20. Mai 2020 20:17 >>>> To: Frank Brockners (fbrockne) <fbrockne@cisco.com>; Nagendra Kumar >>>> Nainar >>>> (naikumar) <naikumar@cisco.com>; 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 >>>> >>>> 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>; Nagendra Kumar >>>>>> Nainar >>>>>> (naikumar) <naikumar@cisco.com>; 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>; >>>>>>>> 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 >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>
- [Tsv-art] Tsvart telechat review of draft-ietf-sf… Frank Brockners via Datatracker
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Nagendra Kumar Nainar (naikumar)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Frank Brockners (fbrockne)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Joel M. Halpern
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Carlos Pignataro (cpignata)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Frank Brockners (fbrockne)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Joel M. Halpern
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Nagendra Kumar Nainar (naikumar)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Frank Brockners (fbrockne)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Frank Brockners (fbrockne)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Joel M. Halpern
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Frank Brockners (fbrockne)
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Joel Halpern Direct
- Re: [Tsv-art] Tsvart telechat review of draft-iet… Nagendra Kumar Nainar (naikumar)