Re: [Anima] Rtgdir last call review of draft-ietf-anima-autonomic-control-plane-24

[Toerless Eckert <[e-mail]>]

Thanks, Joel,

Wrt L2: Always good to explicitly suggest text when that's what you're after.

Not sure why i didn't include this sentence. I guess i didn't even had the
idea that one cuold enable/dible ACP separately on different L2 ports ;-)

Cheers
    Toerless

On Sat, Jul 04, 2020 at 08:59:57PM -0400, Joel M. Halpern wrote:
> My apologies for the delay in responding to these comments.
> The changes seem to nicely address all of my comments.  I hope that I will
> recall this well enough to avoid introducing triple-jeopardy by accident.
> (Having said that, it appears that my pushing on some of these issues a
> second time contributed to your finding good resolutions of the issues.)
> 
> On the 7.2 comments, my primary comment was a mistake on my part.  The only
> configuration required is the same configuration that is required for ACP
> nodes, namely turning on ACP.  (Which may or may not be a default setting,
> but is clearly a configurable behavior.)
> 
> On the comment about a corner case, I was looking for text saying roughly
> "An L2 node that supports ACP and is enabled to participate SHOULD do so on
> all its L2 interfaces.  I grant this is not a big deal. My concern is if the
> L2 link selection is a partial / proper subset of the intended L3
> adjacencies, problems could easily result due to traffic not arriving at all
> desired places.
> 
> Thank you,
> Joel
> 
> On 6/23/2020 10:35 PM, Toerless Eckert wrote:
> > Thanks a lot, Joel
> > 
> > Personal diff with just the fixes for you, otherwise feel free to compare -25 against
> > -25, it has more fixes for Russ Housley and IPsec proto detail enhancements/fixes.
> > 
> > http://tools.ietf.org/tools/rfcdiff/rfcdiff.pyht?url1=https://raw.githubusercontent.com/anima-wg/autonomic-control-plane/0caa400fd1c554ece49fddc7dabe8140195aa5bf/draft-ietf-anima-autonomic-control-plane/draft-ietf-anima-autonomic-control-plane.txt&url2=https://raw.githubusercontent.com/anima-wg/autonomic-control-plane/ae9e6cd856ab2706e8b38cc2552f2e77f6b676a5/draft-ietf-anima-autonomic-control-plane/draft-ietf-anima-autonomic-control-plane.txt
> > 
> > Cheers
> >      toerless
> > 
> > On Thu, Apr 09, 2020 at 07:16:16PM -0700, Joel Halpern via Datatracker wrote:
> > > Reviewer: Joel Halpern
> > > Review result: Not Ready
> > > 
> > > Hello,
> > > 
> > > I have been selected as the Routing Directorate reviewer for this draft. The
> > > Routing Directorate seeks to review all routing or routing-related drafts as
> > > they pass through IETF last call and IESG review, and sometimes on special
> > > request. The purpose of the review is to provide assistance to the Routing ADs.
> > > For more information about the Routing Directorate, please see
> > > ???http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir
> > > 
> > > Although these comments are primarily for the use of the Routing ADs, it would
> > > be helpful if you could consider them along with any other IETF Last Call
> > > comments that you receive, and strive to resolve them through discussion or by
> > > updating the draft.
> > > 
> > > Document: draft-ietf-anima-autonomic-control-plane-24.txt
> > > Reviewer: Joel Halpern
> > > Review Date: 9-April-2020
> > > IETF LC End Date: N/A
> > > Intended Status: Proposed Standard
> > > 
> > > Summary:
> > >      I have two major concern about this document that I think should be
> > >      resolved before publication.  The are also a number of minor items that
> > >      warrant attention.
> > > 
> > > Comments:
> > > 
> > > While quite long, the draft is significantly improved from earlier versions.
> > > It does provide significant explanation of its design choices, which is helpful
> > > and appreciated.  Sometimes this seems to end up more as marketing or promotion
> > > instead of explanation, but this is mostly harmless.
> > 
> > Any pointers to specific text that sounds to be too marketing wise
> > always welcome. Happy to review that. I thought i had eliminated all
> > the ones... i did see myself.
> > 
> > > In particular, I would like to thank the authors and editors for the addition
> > > of section 9.3 and its careful discussion of the many issues there.
> > 
> > Thank you.
> > 
> > > Major Issues:
> > > 
> > >      Section 6.10.3.1 on the use of Zone-IDs seems, from the material in A.10.1,
> > >      to be dependent upon either configuration (which ACP is supposed to avoid)
> > >      or completely unspecified magic.  Having an addressing and routing scheme
> > >      standardized that is impossible to use seems at variance with appropriate
> > >      practice.  It would be fine to say that provision is made for non-zero
> > >      Zone-IDs in the hope that future work can find ways to scale further using
> > >      this.  But pretending it is well-defined, but not actually defining it,
> > >      seems unacceptable.
> > 
> > You brought up this issue in your -13 review and we had a longer thread about
> > it which ended in i think this statement of yours:
> > 
> > | <[e-mail]>
> > | My perspective is that I would have preferred to see the system designed such
> > | that when Zones are needed, they can be added in a way that does not assume
> > | system-wide knowledge of the layout choices.
> > |
> > | I think you could have achieved that.  I understand that the working group
> > | didn't do that.  And beause it is the WG decision, I can live with it.  I wish
> > | it were better.
> > 
> > No protection against double jeopardy in IETF ?
> > Maybe its a good thing except for expediency of completion of the draft,
> > because i had to rethink the issue again, and while it took a while i
> > hope the result is especially good to help with initial ACP adoption
> > challenges:
> > 
> > The included text in the discussion up to -24 is now also in my opinion not very
> > useful, it also had technical issues.
> > The core issue that was combination of your ask for complete removal
> > of the ACP zone address scheme and the (bad) solution of attempting to guess
> > at a future way how to provide the final full benefits for the zone address
> > scheme in 6.10.3.1. And that guesswork in 6.10.3.1 was not good, which is
> > why 6.10.3.1 is now gone in -25.
> > 
> > [Side note: I think i have the zone solution for a future RFC kinda worked out:
> > we would have some manual or autonomic zone edges, grasp announcements within each
> > zone announcing the Zone-ID and then nodes with ACP-Zone addresses that
> > attach into a zone would update the Zone-ID of their ACP address accordingly.
> > E-voila: zone-mobility by updating the zone-id field]
> > 
> > However, the main disconnect was that this longer term goal alone is not
> >   good reason to keep Zone-ID. Instead the main reason to keep it was and is
> > the ability to support better partial and incremental adoption of ACP,
> > and for that one we do actually have good pre-standard implementation
> > experience.
> > 
> > But i didn't want this in the normative part of the spec, and i either
> > didn't get the idea that it could go into the operational part (section 9),
> > or i felt such text would be too difficult or too much subject to additional
> > review attacks.
> > 
> > But given how i think it is really an important option for initial
> > deployments of ACP in large networks, i finally wrote that, it is
> > now a new section 9.4. Pls check it out.
> > 
> > >      Section 6.12.5.1 on loopback interface is factually wrong.
> > >      It conflates one particular form of loopback interface with
> > >      the definition of loopback interfaces.
> > > 
> > >      This also leads to the error in the definition section (see
> > >      minor comment below).
> > 
> > Let me move this here so we can have a cohesive discussion about that section.
> > 
> > >      6.12.5.1 refers to the ACP addresses as node addresses.  Technically, the
> > >      IPv6 architecture requires that all addresses are associated with
> > >      interfaces rather than nodes.  I would prefer that this draft not
> > >      needlessly claim to violate that.
> > 
> > In practice the term node address is often used, maybe less
> > in RFC, but more in practice. And its often done
> > interchangably with loopback addresses because without changing
> > the actual IPv6 functionality, loopback interfaces are the
> > main way to achieve the function operators typically associate
> > with a node address.
> > 
> > Be that as it may, i have tried to end the rewrite of the section
> > with a paragraph that is trying to bring the use of the word "Node"
> > in-line with the way RFC8402 does it.
> > 
> > >     (Loopback Interfaces were used long before RFC 4291,
> > 
> > Yepp, was just bad english to connect something that was meant to be
> > read in he context of IPv4 with an example about IPv6.
> > 
> > >      and on routers were often used for external communication.  This was itself
> > >      a repurposing of the original loopback interface, 127.0.0.1, which was
> > >      indeed for internal use.)
> > 
> > Yepp.
> > 
> > So, i ended up rewriting the whole section also because EricV asked
> > in his review earlier this year if it would not be better to use a new
> > term instead of loopback.
> > 
> > Whe i reviewed existing normaive references it became clear to me that
> > loopback is actually a very good logical name for the function we
> > need for addresses we want to behave as what non-dogmatic people
> > would call a node address. So i hope the explanation in the new
> > text for loopback to well justify the naming choice.
> > 
> > I have also added a bullet list for justifying the loopback address
> > use. Really nothing new, but common operational practice, alas, i
> > wasn't able to find a list like this in other docs and this
> > is an ongoing reason for questions from readers of ACP that do not
> > have a background in running IP router networks.
> > 
> > So hopefully, while this point too took me a lot of time to
> > rewrite, it is all for the better.
> > 
> > > Minor Issues:
> > > 
> > >     It seems distinctly unfortunate that the definition for Data Plane in
> > >     section 2 explicitly states that this definition is different from that used
> > >     in other work, including other routing work.  This seems a recipe for both
> > >     confusion and mis-communication among technologists.
> > 
> > Actually, IMHO the term data-plane has always been badly defined in the
> > face of the inline-signaling model of IP networks. Are IGP/BGP signaling
> > packets data-plane or control-plane ? How about routers connecting via
> > L2 unbeknownst to them and their STP packets ? Even if you have an
> > opininon, do you have a normative RFC to support your definition ?
> > What is the difference between data and forwarding plane ?
> > 
> > Don't answer... rethoric questions...
> > 
> > I have replaced two existing paragraphs in the intro with the following
> > text that explains the terminology better and shows how in the vision
> > of autonomic networks the term is very logical, and that it is just
> > existing non-autonomous networks in which there is more to the data-plane
> > than what you might expect, but i think that is perfectly fine, especially
> > when considering the layering example from above, where one layers (L2, ethernet)
> > control and forwarding plane are just considered to be part of a higher layers
> > data-plane.
> > 
> > New text:
> > <t>In a fully autonomic network node without legacy control or management functions/protocols, the Data-Plane would be for example just a forwarding plane for "Data" IPv6 packets, aka: packets that are not forwarded by the ACP itself because they are control or management plane packets. In such networks/nodes, there would be no non-autonomous control or non-autonomous management plane. Routing protocols for example would be built inside the ACP as so-called autonomous functions via autonomous service agents, leveraging the ACPs functions instead of implementing them seperately for each protocol: discovery, automaticically established authenticated and encrypted local and distant peer connectivity for control and managemenet traffic and common control/management protocol session and presentation functions.</t>
> > 
> > <t>When the ACP is added to henceforth so-called non-autonomous nodes that have non-autonomous management plane and/or control plane functions, the ACP instead is best abstracted as a special Virtual Routing and Forwarding (VRF) instance (or virtual router) and the complete pre-existing non-autonomous management and/or control plane is considered to be part of the Data-Plane to avoid introduction of more complex, new terminology only for this case. Like the forwarding plane for "Data" packets, the non-autonomous control and management plane functions can then be managed/used via the ACP. This terminology is consistent with pre-existing documents such as <xref target="RFC8368">"/>.</t>
> > 
> > <t>In both instances (autonomous and non-autonomous nodes), the ACP is built such that it is operating in the absene of the Data-Plane, and in the case of existing non-autonomous (management, control) components in the Data-Plane also in th
> > e presence of any (mis-)configuration thereof.</t>
> > /New text
> > 
> > >     In the definition of in-band management in section 2, please remove the
> > >     commentary text on putative fragility.   (I actually agree it has some
> > >     fragility.  The discussion does not belong here.  This is a definition.)
> > >     The promotional material may be warranted, if jarring, in other parts of the
> > >     documents.  Not in the definitions please.
> > 
> > Ok, i stripped down explanatory text for out-of-band network in terminology
> > and instead pimped what you would call "marketing" about it in the introduction section. Easy to find in diff.
> > 
> > Always happy to get explicit suggestions for how to reduce what you think
> > is "jarring". The ability of ACP to even avoid a single case of sending
> > out a tech person to a remote site due to misconfigurations is IMHO
> > the bigest single use-case benefit in talks with customers, so i think it deserves
> > good factual representation and i can not see where the text goes beyond
> > that. I am happy if any positive pitching is called "marketing", but
> > i definitely do not want anything to be "jarring".
> > 
> > >      The definition of a loopback interface in section 2 is wrong.  It claims
> > >      that loopbacks transmit no external traffic.   They send and receive lots
> > >      of external traffic.  They merely do so by forwarding the traffic
> > >      internally to other interfaces.  The traffic is external.  The particular
> > >      step of the transmission, if implemented naively, is internal.
> > 
> > Fixed.
> > 
> > >      If we are going to define ACP as a virtual out of band network, I would
> > >      suggest separating the terms into two definitions. One for true out  of
> > >      band networks (distinct physical links, switches, and ports), and then a
> > >      definition for virtual out of band network which describes the ACP
> > >      approximation which creates independence from configuration, but not
> > >      independence from the physical links.
> > 
> > Done.
> > 
> > [ Note: I am btw. not worried about the link-sharing as a career limiting move
> >    for ACP, as soon as there is sufficient link redundancy (2 links eliminate 99% of issues).
> > 
> >    The actual HW design of the nodes to maximize ACP value is more interesting.
> >    I had slides about that in a research conference workshop some years back, e.g.: applying
> >    concepts such as BMC so that you can use the common HW diag functions
> >    you typically expect from OOB support. ]
> > 
> > >      Section 5, bullet 2, talks about a policy as to which peers ACP
> > >      communication should be established.  It would be helpful if this gave a
> > >      reference or indication as to where such policies would come from.  Given
> > >      the emphasis on zero touch, I presume they are not configured on the node?
> > >      (This issues was in my review of -13.)
> > 
> > Original -13 thread here:
> > 
> > | >>      It is unclear how the flexible policy defined in section 5 bullet 2 (about
> > | >>      which nodes are ACP peer candidates) is consistent with autonomic
> > | >>      operation.  It seems that the flexibility is important, so there should be
> > | >>      some explanation here about how this is consonant with the stated goals.  I
> > | >>      understand that the bootstrap comes from BRSKI, but I do not think that is
> > | >>      where the policy comes from?
> > | >
> > | > Would rather not like to add more suggestive text, and thats at best what
> > | > i could add. The default policy is the best "autonomic" behavior we know how
> > | > to make work: aka: try to connect ACP to all neighbors you can discover. And
> > | > we have only defined with DULL GRASP how to find subnet adjacent neighbors.
> > | >
> > | > The main reason to mention policy is so that there is some leeway to do
> > | > more or even (sigh) less than all direct neighbors.
> > 
> > Double jeopardy ?
> > 
> > I actually did not bother to fix up the intro section since taking the editor pen
> > from Michael. I had kept the "policy" in there as a reminder of Intent to be
> > done in the future, but given how we deprioritized
> > intent in charter, i felt more happy now than during 13 to fix this.
> > 
> > Alas, it turns out i also found other points in the overview lacking
> > clarity and consistency with the normative sections, so the changes
> > here got larger, but hopefully all for the better. Please check.
> > 
> > >      Bullet 4 of section 6.1.3 on checking certificates against the CRL / OCSP
> > >      would seem to be better reworded.  I believe the intended requirements i
> > >      that IF there is ACP connectivity to the CRL / OCSP source, then it should
> > >      be verified.  But that absence of such connectivity should not prevent
> > >      association formation.  (As, if I have read it wright, otherwise we could
> > >      deadlock the startup process.)
> > 
> > Pls. check the full diff vs. -24 for this, because that fix is in the commit i did for
> > Russ Housley before i worked on your review. If you don't like that text either, pls
> > suggest better wording, its a bit of a tricky language problem i think, which a native
> > speaker might master easier.
> > 
> > >      In the example in section 6.5 on Channel selection, in steps 7:C1 and
> > >      11:C2, Node 1 concludes that it is Bob.  However, in steps 12 and 13, the
> > >      text refers to Node1 (Alice).  This seems inconsistent.
> > 
> > Yikes. How could that have slipped me. Thanks a lot.
> > > 
> > >      Section 6.7.1 makes an assertion about the lack of need for MTI of security
> > >      mechanisms.  The earlier explanation was well done and seems sound.  This
> > >      shorter one seems wrong, since without MTI there is no good way to know
> > >      what ones neighbors may implement.  I suggest simply removing this text and
> > >      replacing it with a backwards reference to the earlier description.  (The
> > >      rest of the section is useful and clear.)
> > 
> > Done.
> > 
> > >      In 6.10.3,  ACP Zone Addressing Sub-Scheme, the text claims that when zone
> > >      IDs of 0 are used, the addresses are identifiers, and when non-zero IDs
> > >      aere used, they are locators.  Since in either case the addresses are used
> > >      for packet forwarding, and the addressing information is propagated in the
> > >      routing protocol (RPL), this seems to be a misuse of the locator /
> > >      identifier distinction.  And a misuse for no purpose as the distinction is
> > >      not relevant to the document.  (This odd use of "identifier continues in
> > >      section 6.10.3.1.  Identifier is not a synonym of "flat".  Just say "flat".)
> > 
> > Hey, i didn't come up with all this confusing an probably wrong understanding
> > of locator or identifier, i just fell into the trap of trying to use these terms ;-))
> > 
> > This is removed now. Hope i found all places. Only locartors left should be
> > about GRASP.
> > 
> > Is there even any agreed upon distinction ? To me, identifier/locator are just
> > two roles an address can have based on who is using it for what purpose.
> > They're not exclusive to each other IMHO.
> > 
> > >      The assertion about looping packets in the later portion of 6.11.1.1 is
> > >      over-stated.  There are other routing protocols that avoid looping-till-ttl
> > >      without changing the data plane header.
> > 
> > >      I suggest removing the gratuitous     comparison with other routing protocols.
> > 
> > Well... it was IMHO not gratuitous, it was just bad text.
> > 
> > The intent was not to make the solution sound better than other routing protocols,
> > but rather to explain how it is not far worse than other routing protocols given
> > the absence of the RPI (RPL Packet Information).
> > 
> > The text was not good because it only indirectly addressed what
> > it intended to describe by just talking about TTL looping. I have replaced this
> > paragraph by two paragraphs that hopefully better capture the intent:
> > 
> > [snip]
> >      <t>
> >        In RPL profiles where RPL Packet Information (RPI, see <xref target="rpl-Data-Plane"/>)
> >        is present, it is also used to trigger reconvergence when misrouted, for example looping, packets
> >        are recognized because of their RPI data. This helps to minimize RPL signaling traffic
> >        especially in networks without stable topology and slow links.
> >      </t>
> >      <t>
> >        The ACP RPL profile instead relies on quick reconverging the DODAG by
> >        recognizing link state change (down/up) and triggering reconvergence signaling
> >        as described in <xref target="rpl-dodag-repair"/>.  Since links in the ACP
> >        are assumed to be mostly reliable (or have link layer protection against loss)
> >        and because there is no stretch according to <xref target="rpl-dodag-repair"/>,
> >        loops caused by loss of RPL routing protocol signaling packets should be exceedingly rare.</t>
> >      </t>
> > [/snip]
> > 
> > Hope this is an adequate answer to close this point.
> > 
> > I now have no text about TTL expiry because that is a difficult qualitative
> > comparison for which there is IMHO not enough data on evidence: The
> > reconvergence with RPL in the ACP profile may be somewhat slower than
> > the most common sub-50 msec LFA in SP networks or subsecond SPF-IGP
> > fast convergence common in most other networks in scope of ACP ("well manageg,
> > aka: private enterprise etc. networks), but the total amount of traffic
> > across the ACP will likely be orders of magnitude less than that on the
> > Data Plane where the SPF-IGP runs.
> > 
> > I think convergence with the profile should be 50 msec (link change discovery
> > plus O(max-pathlength) * per-node RPL processing latency, but i think
> > this is too much analysis for a spec, so no text.
> > 
> > >      Section 7.2 (L2 DULL GRASP) seems to be doing something quite useful.  I
> > >      think I see how it would work.  The need for some configuration on some
> > >      switches seems inevitable and acceptable.
> > 
> > Hmm.. there is no intent to require configuration. What specifically
> > do you think of ?
> > 
> > The goal is really to support ACP in complete L2-only networks, except that
> > the ACP itself is of course L3.
> > 
> > One core part of the text is explaining how ACP can be supported
> > on the most limited L2 hardware where it can work. Aka: withough changing
> > the actual L2 HW forwarding, but just by punting GRASP packets so they
> > are not flooded by L2.
> > 
> > >      I think there is one corner
> > >      case that should be avoided, as it seems likely to create significant
> > >      complexity for little or no benefit.  It seems to me that a switch that is
> > >      capable of participating in the ACP should either participate in the ACP on
> > >      all its physical ports, or should not participate in the ACP at all.  I
> > >      would not be surprised if that was the WG intent.  But I could not find the
> > >      text that says this.  (Apologies if it is there and I missed it.)
> > 
> > Not sure why you specifically think this is an issue for devices
> > operating at L2.
> > 
> > I have seen all type of weird problems. For example: How do you
> > enable autodiscovery of ACP neighbors across the 10Gbps backbone
> > interfaces of a router/switch for broadband if those interfaces
> > are initially disabled by software because the user is expected
> > to first enter an additional license key to use those interfaces....
> > 
> > Sorry, randomn example. Maybe rephrase your point with an example
> > why you think it deserve additional text ? Suggest additional text ?
> > 
> > > 
> > >      Section 9 starts by saying it is informational.  But the first paragraph
> > >      says that some of the content is "necessary" for correct operation.  Thus,
> > >      it seems that some of the content is normative?   (I am not sure, but I
> > >      think the "necessary" material relates to what is needed to be a registrar?)
> > 
> > The first paragraph does not say "correct operation", and i think
> > to remember that i word smithed that paragraph quite
> > a bit to walk the thin line: you can not build an ACP without
> > understanding this section and follow its advice to
> > the extend you deem appropriate or feasible, but we can also not
> > normatively standardize what is in this section.
> > 
> > Some things will hopefully gt standardized via future
> > yang model RFC. That stuff is just not standardized beause
> > it does not meet the formal bar.
> > 
> > Most of the stuff is talking about variety of options
> > deemed to be necessary or beneficial in various
> > situations. Doing even the Yang stuff for the subset
> > people will agree to is a lot of work.
> > 
> > protecting the ACP from operator
> > misconfiguration is IMHO necessary. I wouldn't even dare
> > to begin guessing what details could get standardized for
> > that. Yang models for new interface states would certainly
> > be another 5++ year discusion in IETF. better to start
> > these things with vendor proprietary Yang models and learn.
> > 
> > I know from personal experience that you can not successfully
> > deploy without humunguous amount of diagnostic as long as
> > you have buggy implementations, especially when fitting
> > into exising router OS, incurring a lot of unforeseen
> > limitations. Very difficult to standardize because its
> > all about interaction with the non-autonomic stuff unless
> > you can severely isolate ACP in your platform design.
> > 
> > If you do not understand the discussions about registrars,
> > you will have a hard time getting a working support
> > backend system for the registars.
> > 
> > Aka: necessary does not mean standardizable.
> > 
> > > Nits:
> > >      The second and third paragraphs of section 6.11.1.1 on RPL start with
> > >      duplicated text, and then go on to say different (complementary) things.
> > >      There is no need for the repetition.
> > 
> > Right. I reworked the overview to remove duplicates, also structured
> > into two subsections to highlight the two key themes of the profile
> > (single instance and convergence).
> > 
> > >      The rank factor in 6.11.1.6 of 100 megabits as the boundary seems a fairly
> > >      arbitrary choice.  It may be that an arbitrary choice was needed.  Could
> > >      something be said?  In particular, if someone looks at this 5 years from
> > >      now, it may seem quite confusing.
> > 
> > In german, rule of thumb is called "pi times thumb", obviously much more
> > accurate than just thumb ;-)
> > 
> > I added the following paragraph:
> > 
> >          <t>This is a simple rank differentiation between typical "low speed"
> >          or "IoT" links that commonly max out at 100 Mbps and typical
> >          infrastructure links with speeds of 1 Gbps or higher. Given how
> >          the path selection for the ACP focusses only on reachability but
> >          not on path cost optimization, no attempts at finer grained path
> >          optimization are made. </t>
> > 
> > Heard a nice summary about the new ieee work about the future of 10 Mbps
> > ethernet over twisted pair, so i think the cut point at 100 Mbps
> > may actually be quite a good one. aka: with just two values i don't
> > know how we could do better.
> > 
> > Aain, thanks a lot for the review.
> > 
> > Toerless
> > 

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