Aijun, Your email is written prove that my question the other day which remain not answered is valid.
I asked is the scope of PUA/PULSE to only signal service endpoints or is this to also carry any to any liveness across all areas/levels in the link state IGP ? It seems clear that you say is the latter. Not sure if PULSE authors are of the same opinion. If every node is interested in every other node's liveness that we are redefining scope of the work here, but I may still argue that not every node in the network will have a segment endpoints terminating on every other node. So registration model handled outside of active link state nodes IMO still is far superior to flood and forget (via timeout) type of model. Best, R. On Tue, Mar 29, 2022 at 3:40 AM Aijun Wang <wangai...@tsinghua.org.cn> wrote: > Hi, Robert: > > Let’s don’t make the conclusion in hurry. > > I think you should know the application scenarios for such unreachable > information is not only for BGP services, but also for the tunnel > services(for example, SRv6 loose-path routing). > > For the latter scenario, the P node on the path should know the status of > other P node on the path, which is located in other areas. > > Then, NLP like approach will also result in ALL NODES within the areas > needs to register such information, and the failures of one nodes will be > sent to all the register. > > What’s the difference with the IGP flooding mechanism then? > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* Robert Raszuk <rob...@raszuk.net> > *Sent:* Monday, March 28, 2022 5:01 PM > *To:* Aijun Wang <wangai...@tsinghua.org.cn>; Tony Li <tony...@tony.li> > *Cc:* Aijun Wang <wang...@chinatelecom.cn>; lsr <lsr@ietf.org> > *Subject:* Re: [Lsr] Is it necessary to define new PUB/SUB model to > monitor the node live? > > > > Aijun, > > > > > For PUAM, the receiver NEED NOT register anything. > > > Once the node fails, all the receivers(normally the nodes within one > area) will be notified. > > > > That's a spec bug not a feature. > > > > Not only those egress nodes which would have otherwise register will get > it with PUAM, but also all P nodes in the area which do not have any > interest what so ever will also get it. > > > > Worse - EVERY IGP NODE - in all areas/levels will get it. > > > > Can't you see how bad architecturally that is ? And I do not buy the > justification - oh this is so little or - oh this is likely to never > happen ... If that is so why bother when you can just either do it with > pub-sub model or simply withdraw your service routes (either one by one or > in bulk mode) ? > > > > Thx, > R. > > > > PS. And if you like analogies - We are here about speed to service > restoration - correct ? So what is better - to signal node failure using as > a carrier a local train which requires to change trains at each of say 30 > stations or put the information into a RAPID one which only stops at two > exchange stations ? > > > > > > > > On Mon, Mar 28, 2022 at 3:15 AM Aijun Wang <wangai...@tsinghua.org.cn> > wrote: > > Hi, Tony: > > Let’s focus on the comparison of NLP and PUAM(Prefix Unreachable > Announcement Mechanism): > > For NLP, the receiver should register the interested prefixes first. Once > the node fails, all the receivers(normally the nodes within one area) that > register such interested prefixes will be notified. > > For PUAM, the receiver NEED NOT register anything. Once > the node fails, all the receivers(normally the nodes within one area) will > be notified. > > > > From the POV of the receiver, if it gets the same results, why don’t > select the approach that need less work or nothing to do? > > > > And regarding to your arguments of “Dump Truck” worry about IGP protocol, > I think defining one new protocol does not solve the ultimate pressure on > Router. Let’s explain this via one analogy: > > The customer(Operator) want the truck(IGP Protocol) to piggyback(via some > Tag) some information, the driver(Vendor) said he can’t, because the > truck may crush the station(Router) when it pass. The operator need another > truck(New Protocol) to carry it. > > > > Here is the problem then, from the POV of station(Router), if it can’t > endure the pass of one truck, why can it can stand to pass the two trucks > at the same time? > > Wish you can explain the above paradox in reasonable/logical manner. > > > > Best Regards > > > > Aijun Wang > > China Telecom > > > > *From:* lsr-boun...@ietf.org <lsr-boun...@ietf.org> *On Behalf Of *Tony Li > *Sent:* Friday, March 25, 2022 7:20 PM > *To:* Aijun Wang <wang...@chinatelecom.cn> > *Cc:* lsr@ietf.org > *Subject:* Re: [Lsr] Is it necessary to define new PUB/SUB model to > monitor the node live? > > > > > > Hi Aijun, > > > > Thanks for your clarification of the NLP mechanism during the meeting. > > 1. Regarding to the PUB/SUB model within IETF, there are already some > of them: > > 1) https://datatracker.ietf.org/doc/html/rfc8641 (Subscription to > YANG Notifications for Datastore Updates) > > 2) https://datatracker.ietf.org/doc/html/draft-ietf-lisp-pubsub-09 > > 3) https://datatracker.ietf.org/doc/html/draft-ietf-ace-pubsub-profile > > 4) > https://datatracker.ietf.org/doc/html/draft-ietf-core-coap-pubsub-09 > > Why do we need to invent the new one again? > > > > > > Thank you, I was unaware of these. If the WG is interested, I’m > certainly willing to pursue using one of these. > > As far as I can tell from a quick perusal, none of these is intended to be > generic. That is to say, none of them > > is a dump truck either. > > > > > > And, if we prefer to the PUB/SUB model to solve the discussed problem, why > RFC8641 can’t be used? > > > > > > YANG is evil. :-) > > > > > > 2. Regarding to the NLP mechanism itself: > > As you explained, current NLP adopt the “Subscribe Summary Prefixes, > Notify the failure of Specific Address” to reduces the pressures on ABRs. > Such approach has the following drawbacks again: > > 1) The register should know in advance the summary prefixes that the > peers‘ loopback address belong to. Once the summary prefixes are changed, > such information should be updated, which will be headache for the operators > > > > > > Not at all. Loopback address configuration is already handled by the > management plane. A prefix or multiple prefixes for loopback addresses will > also be incorporated into the management plane. > > > > Modern networking assumes automation. Yes, we didn’t have it back when I > started, but it’s there today. Admittedly, it’s not perfect and it has a > way to go, but there are MANY organizations now that are fully automated. > Anyone that wants to be, can be. > > > > > > 2) If the register subscribe the “summary prefixes”, then it will > receives all the nodes fail notifications within this summary prefixes, > which should be avoided when you argue that IGP flooding has such side > effect.----The results is, NLP can’t avoid it also, then why don’t we > utilize IGP flooding mechanism directly? > > > > > > Yes, if you register for a prefix, you may get multiple notifications > back. This is a good thing. In the IGP, this would create a scalability > problem. The very good news is that this is not a scalability problem for > NLP. There is no restriction for a finite sized LSDB. There are no > real-time demands. The distribution of the data can be easily managed, even > for slow receivers, by techniques that are well-known for BGP. > > > > Using a real transport protocol instead of relying on flooding is a Very > Good Thing. And don’t get me wrong, I love flooding. For the things that > should be flooded. :) > > > > > > 3) The controller is already in the network, why not rely on it to > relieve the pressure of ABRs if we prefer to the PUB/SUB model to solve the > questions. And, as you stated, the NLP mechanism may be used to transfer > other non-IGP information, then why bother ABR? > > > > > > Yes, we can also solve the PUA problem via a controller. If the WG chooses > to take that path, it can. Heck, we could choose to say that we believe in > the SDN philosophy completely and that IGPs should be deprecated in favor > of SDN. Of course, this also addresses the PUA problem. :) > > > > Tony > > > > _______________________________________________ > Lsr mailing list > Lsr@ietf.org > https://www.ietf.org/mailman/listinfo/lsr > >
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