Re: [Roll] review of dao-projection -21
Michael Richardson <mcr+ietf@sandelman.ca> Tue, 23 November 2021 10:46 UTC
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From: Michael Richardson <mcr+ietf@sandelman.ca>
To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>, Routing Over Low power and Lossy networks <roll@ietf.org>
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Date: Tue, 23 Nov 2021 05:45:52 -0500
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Subject: Re: [Roll] review of dao-projection -21
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Pascal Thubert (pthubert) <pthubert@cisco.com> wrote: >> Rahul and I (via hypothys.is) want to know why "anistropic" was part of >> the introduction sentence. It's not wrong, but it seems funny to >> suddenly have this so prominent. > I opened a separate thread for this. What is hypothys.is ? A group commenting system that Rahul and I happen to both use. (Who remembers Netscape Group Annotations?... ) >> You might want to consider upgrading to kramdown for your source, and >> then change your ascii art to something goat can upgrade to SVG. >> https://github.com/blampe/goat > I'm not that fond of kramdown, that's an extra step for me, and I use it when I must. > Goat seems orthogonal, I love it but lack time for fun to learn through the IETF procedure. > Look at https://www.ietf.org/archive/id/draft-ietf-rift-rift-13.pdf; good yes, perfect, no. Worth the effort ? Yes, worth the effort. Goat lets you write ASCII art in a slightly restricted way, and it upgrades it to SVG. The reason to use kramdown here is only because it manages that for you. >> A major issue for me is how things get turned on. >> Does this document wait for capex? probably? I know that I'm probably >> the slow/weak link in the capex chain. > It would have largely benefitted from capex if capex was there. > For now it will be configuration / management. So I can use it only after I know that all nodes support it. > See section 3.7 " > The "6TiSCH Architecture" [6TiSCH-ARCHI] leverages a centralized > model that is similar to that of "Deterministic Networking > Architecture" [RFC8655], whereby the device resources and > capabilities are exposed to an external controller which installs > routing states into the network based on its own objective functions > that reside in that external entity. > " > The management magic tells the root which node supports this and their > capacity. It's all done outside RPL. I'm okay that the PCE/Root interface is outside RPL, and even that it's non-standard. Some roots could include the PCE internally, I think. > " > With this specification, an abstract routing function called a Path > Computation Element [PCE] (e.g., located in an central controller or > collocated with the Root) interacts with the RPL Root to compute Peer > to Peer (P2P) paths within a pre-existing RPL Main DODAG. " >> The document says, "Root or an associated PCE " a few times, so maybe >> we could just call it the "P-DAO engine" or something like that. > I like using the standard term if that's abstract enough Works for me. >> Maybe, instead of trying to make a definition list for this section, >> make subsections, because I think that each term here actually requires >> more than a sentence. >> >> _subTrack_ or sub-track? >> 1) Not fond of camelcase in specifications. > This is common with the RAW architecture. I can uplift both but it's > work to do and undo, so I'd like to see a consensus. > Maybe make it an item to resolve for the WGLC? okay. > " > 2.4.4. Routing Stretch: > RPL is anisotropic, meaning that it is directional, or more exactly > polar. RPL does not behave the same way "down" with multicast DIO [wearing my dad-is-teenager-chemistry-tutor hat now wants to know if routing can be both covalent and polar... ] > The term Routing Stretch denotes the length of a path, as compared > with a shortest path, which can be a abstract concepts in RPL when > the metrics are statistical and dynamic, and the concept of short > varies with the Objective Function. Thanks >> >> section 3.4: >> "so-called Track Legs" ... I think the terminology says they are called >> Track Legs, so I think "so-called" is unneeded text. >> (ps: so now I have ZZtop in my head: >> https://www.youtube.com/watch?v=eUDcTLaWJuo ) > Excellent! Done. The text can be a bit more explicit, more in the full excerpt below; But, can we make ZZtop the theme song for this document? :-) "RPL has Legs... and PCE knows how to use them!" >> "stitching" point... needs a definition, I think. > " > 2.4.9. Stitching: > This specification using the term stitching to indicate that a track > is piped to another one, meaning that traffic out of the first is > injected in the other. > " > Works? Good. >> I suggest section 4 identify when it Updates, whether it is Amending, > Argll you're killing me :) I still do not understand what "updates" means and now we amend? There is a document trying to detail this, I'm just suggesting we get ahead of that. > We do not break anything in existence if that is the question. Amends doesn't mean break... it means that there is new work. > Following your line of thought I should make that a different section, > but it seems to me with this is really too picky. if you can imagine a project manager assigning the work to two different people, then a new section would help. "Bob, implement 4.5.6.9. Sian, implement 4.5.6.8" > I already created many sections in the definition ad in section 3. This > will be the draft of one sentence per section. That's okay with me, if they need to be easily referenced. As, it, "Hey other implementer, you didn't do 4.5.6.7 correctly!" >> Last paragraph of 4.1.1 is about TIO/RIO, and deserves it's own Amends >> section. > I do not see why that is an amendment? The TIO/RIO discussion is today's RPL as is. okay. >> I think that the 3-way-ness of this should be in the intro. > Let's take that as a potential addition to be discussed on the ML, too > big for me to yes/no just here okay. >> section 6.4: >> The SRH-6LoRH with the Via Addresses in the NSM-VIO are not needed >> and MUST be omitted. -> >> The SRH-6LoRH with the Via Addresses in the NSM-VIO are not needed >> and MUST >> be ignored by the receiver. >> >> (I always prefer to tell the receiver what to discard, rather than tell >> the sender what to omit) > OK still sending it wastes energy and may cause a packet loss. What about Of course, it's stupid to send stuff that is not necessary. Until... it becomes necessary, so knowing how the receiver will respond is the important detail. >> 6.5.2: >> "It makes sense to add a new Leg before removing one that is >> misbehaving, and switch to the new Leg before removing the old. >> " >> >> does it? if the old one is misbehaving, wouldn't removing it send >> traffic up to the root (according to non-optimized flow), allowing >> traffic to flow rather than get dropped? yes, there are some cases >> where this doesn't work. > " > It makes sense to > add a new Leg before removing one that is becoming excessively lossy, > and switch to the new Leg before removing the old. Dropping a Track > before the new one is installed would reroute the traffic via the > root; this may augment the latency beyond acceptable thresholds, and > load the network near the root. This may also cause loops in the > case of stitched Tracks; the packets that cannot be injected in the > second Track may be routed back at reinjected at the Ingress of the > first." Works for me. >> section 8: i like these profiles. We do need diagrams. >> (again, SVG and goat may be very nice to use) Do the profiles >> need to be announced in some place in the protocol? > Argl, I do not see that. Hopefully not? okay. >> >> section 9: I don't think that the new risk for forged P-DAOs is >> adequately >> explained. Can we at least authenticate P-DAO messages >> because they >> come from the Root? Sometimes the Root IP address is the same >> as the DODAGID. >> (but not always? I forget) > For P-DAO it is, yes. But we do not secure messages from the root. That > would be nice. How can we do that? I'm okay if we say that only the root (identified by IP address) can send them. >> RFC9008 probably has >> provided all the primitives. (I hope!) But, I'd like to see a state >> machine of sorts that relates the P-DAO, DAO-ACK and PDR/PDR-ACK >> messages. > Again, I'd like to see this agreed by the WG. Would that be normative? Probably. >> I fear that the SHOULD/MUSTs/new-ICMPs messages are too spread over the >> document. > The previous review caused some restructuring. The more we do that the > more we spread. What do we prefer, stricture vs. MUSt concentration? Well, if we had the 6LR changes with state machine, then all the MUSTs would migrate to that section. -- Michael Richardson <mcr+IETF@sandelman.ca> . o O ( IPv6 IøT consulting ) Sandelman Software Works Inc, Ottawa and Worldwide
- [Roll] review of dao-projection -21 Michael Richardson
- Re: [Roll] review of dao-projection -21 Pascal Thubert (pthubert)
- Re: [Roll] review of dao-projection -21 Michael Richardson
- Re: [Roll] review of dao-projection -21 Rahul Jadhav
- Re: [Roll] review of dao-projection -21 Pascal Thubert (pthubert)
- Re: [Roll] review of dao-projection -21 Michael Richardson
- Re: [Roll] review of dao-projection -21 Pascal Thubert (pthubert)