Hi Chris
Just about every vendor out there recommended best practice is to layout address plan to take advantage of summarization wherever possible and that as well includes PE loopback next hop attribute to limit the router load as well as size of LSDB in the backbone as well as domain wide. I think you would be hard pressed to find any vendor that would say go ahead and flood loopbacks domain wide and don’t summarize. In large domains flooding domain wide is not feasible and summarization is requirement even for the critical loopback BGP next hops for most operators. RFC 5302 talks about the ramifications of flooding in ISIS domain in section 1.2 excerpt below: 1.2 <https://datatracker.ietf.org/doc/html/rfc5302#section-1.2>. Scalability The disadvantage to performing the domain-wide prefix distribution described above is that it has an impact on the scalability of IS-IS. Areas within IS-IS help scalability in that LSPs are contained within a single area. This limits the size of the link state database, which in turn limits the complexity of the shortest path computation. Further, the summarization of the prefix information aids scalability in that the abstraction of the prefix information removes the sheer number of data items to be transported and the number of routes to be computed. It should be noted quite strongly that the distribution of prefixes on a domain-wide basis impacts the scalability of IS-IS in the second respect. It will increase the number of prefixes throughout the domain. This will result in increased memory consumption, transmission requirements, and computation requirements throughout the domain. It must also be noted that the domain-wide distribution of prefixes has no effect whatsoever on the first aspect of scalability, namely the existence of areas and the limitation of the distribution of the link state database. Gyan On Fri, Jan 14, 2022 at 9:07 PM Christian Hopps <[email protected]> wrote: > Yes, having worked intimately with these IGPs for > 20 years now, I > understand the use and the implications of using summary routes. :) > > My opinion remains unchanged. > > Thanks, > Chris. > [as wg member] > > > On Jan 14, 2022, at 8:50 PM, Aijun Wang <[email protected]> > wrote: > > > > Hi, Christian: > > > > We should consider the balance and efficiency for the summary or not > summary. > > If you don’t summary, then all the areas will be filled with the > specified detail routes(all PE’s loopback, may also include all P’s > loopback). This can certainly increase the burden of the routers. > > > > But with summary, all these specific routes need not exist in the > routing table. The nodes within the IGP need only be notified when one node > is failure to accelerate the switchover of the overlay service. > > And, you can also select to not using such mechanism, then the service > will be backhole for some time until the service/application find this > abnormal phenomenon. > > PUA/PULSE are just the mechanism to reduce the abnormal durations, it is > one kind of FRR technique. > > > > Aijun Wang > > China Telecom > > > >> On Jan 15, 2022, at 09:26, Christian Hopps <[email protected]> wrote: > >> > >> > >> > >>> On Jan 14, 2022, at 8:25 PM, Christian Hopps <[email protected]> > wrote: > >>> > >>> I understand the proposal. As I've stated elsewhere, I do not believe > there is a problem here that needs solving. The "problem" was created by > the user by summarizing prefixes that should not have been summarized -- > they mis-configured their network. The routing protocols works just fine > (act very quickly) if you don't incorrectly summarize "really important > prefixes". > >>> > >>> I was simply pointing out that IGPs also don't deal in liveness since > that keeps coming up. > >> > >> Sorry that was "as wg member". > >> > >>> > >>> Thanks, > >>> Chris. > >>> > >>>>> On Jan 14, 2022, at 8:06 PM, Aijun Wang <[email protected]> > wrote: > >>>> > >>>> Hi, Christian and John: > >>>> > >>>> No. I think you all may misunderstand the proposal. What we are > detecting is actually the reachability/liveness of node that connected to > the application, not the application itself. > >>>> And, I think the node liveness is same as the node reachability. They > will all influence or break the path to their connected service if their > forwarding function is failed. > >>>> > >>>> Aijun Wang > >>>> China Telecom > >>>> > >>>>> On Jan 15, 2022, at 08:56, Christian Hopps <[email protected]> > wrote: > >>>>> > >>>>> Indeed, and in fact the IGP should only be dealing with the > reachability to the node, not with the node or applications liveness. > >>>>> > >>>>> Thanks, > >>>>> Chris. > >>>>> [as wg member] > >>>>> > >>>>>> On Jan 14, 2022, at 7:47 PM, John E Drake <[email protected]> > wrote: > >>>>>> > >>>>>> I don’t think so. Today things just work, at a given time scale. > What you said you are trying to do is reduce the time scale for detecting > that an application on a node has failed. However, conflating the health > of a node with the health of an application on that node seems to be > inherently flawed. > >>>>>> > >>>>>> Yours Irrespectively, > >>>>>> > >>>>>> John > >>>>>> > >>>>>> > >>>>>> Juniper Business Use Only > >>>>>> From: Aijun Wang <[email protected]> > >>>>>> Sent: Friday, January 14, 2022 7:40 PM > >>>>>> To: John E Drake <[email protected]> > >>>>>> Cc: Les Ginsberg (ginsberg) <[email protected]>; Robert Raszuk < > [email protected]>; Christian Hopps <[email protected]>; Shraddha Hegde < > [email protected]>; Tony Li <[email protected]>; Hannes Gredler < > [email protected]>; lsr <[email protected]>; Peter Psenak (ppsenak) < > [email protected]> > >>>>>> Subject: Re: [Lsr] BGP vs PUA/PULSE > >>>>>> > >>>>>> [External Email. Be cautious of content] > >>>>>> > >>>>>> When the node is up, all the following process are passed to the > application layer. This is the normal procedures of the IGP should do. > >>>>>> According to your logic, IGP are solving the wrong problem now? > >>>>>> > >>>>>> Aijun Wang > >>>>>> China Telecom > >>>>>> > >>>>>> > >>>>>> On Jan 15, 2022, at 08:30, John E Drake <jdrake= > [email protected]> wrote: > >>>>>> > >>>>>> > >>>>>> Correct, but as Tony, Robert and I have noted, a node being up does > not mean that an application on that node is up, which means that your > proposed solution is probably a solution to the wrong problem. Further, > Robert’s solution is probably a solution to the right problem. > >>>>>> > >>>>>> Yours Irrespectively, > >>>>>> > >>>>>> John > >>>>>> > >>>>>> > >>>>>> Juniper Business Use Only > >>>>>> From: Aijun Wang <[email protected]> > >>>>>> Sent: Friday, January 14, 2022 5:53 PM > >>>>>> To: John E Drake <[email protected]> > >>>>>> Cc: Robert Raszuk <[email protected]>; Les Ginsberg (ginsberg) < > [email protected]>; Christian Hopps <[email protected]>; Shraddha Hegde < > [email protected]>; Tony Li <[email protected]>; Hannes Gredler < > [email protected]>; lsr <[email protected]>; Peter Psenak (ppsenak) < > [email protected]> > >>>>>> Subject: Re: [Lsr] BGP vs PUA/PULSE > >>>>>> > >>>>>> [External Email. Be cautious of content] > >>>>>> > >>>>>> Hi, John: > >>>>>> Please note if the node is down, the service will not be accessed. > >>>>>> We are discussing the “DOWN” notification, not the “UP” > notification. > >>>>>> > >>>>>> Aijun Wang > >>>>>> China Telecom > >>>>>> > >>>>>> > >>>>>> On Jan 15, 2022, at 00:25, John E Drake <jdrake= > [email protected]> wrote: > >>>>>> > >>>>>> > >>>>>> Hi, > >>>>>> > >>>>>> Comment inline below. > >>>>>> > >>>>>> Yours Irrespectively, > >>>>>> > >>>>>> John > >>>>>> > >>>>>> > >>>>>> Juniper Business Use Only > >>>>>> From: Lsr <[email protected]> On Behalf Of Robert Raszuk > >>>>>> Sent: Monday, January 10, 2022 7:15 PM > >>>>>> To: Les Ginsberg (ginsberg) <[email protected]> > >>>>>> Cc: Christian Hopps <[email protected]>; Aijun Wang < > [email protected]>; Shraddha Hegde <[email protected]>; Tony > Li <[email protected]>; Hannes Gredler <[email protected]>; lsr < > [email protected]>; Peter Psenak (ppsenak) <[email protected]> > >>>>>> Subject: Re: [Lsr] BGP vs PUA/PULSE > >>>>>> > >>>>>> [External Email. Be cautious of content] > >>>>>> > >>>>>> Hi Les, > >>>>>> > >>>>>>> You seem focused on the notification delivery mechanism only. > >>>>>> > >>>>>> Not really. For me, an advertised summary is like a prefix when you > are dialing a country code. Call signaling knows to go north if you are > calling a crab shop in Alaska. > >>>>>> > >>>>>> Now such direction does not indicate if the shop is open or has > crabs. > >>>>>> > >>>>>> That info you need to get over the top as a service. So I am much > more in favor to make the service to tell you directly or indirectly that > it is available. > >>>>>> > >>>>>> [JD] Right. Just because a node is up and connected to the > network does not imply that a given application is active on it. > >>>>>> > >>>>>> Best, > >>>>>> R. > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>>> > >>>>>> On Tue, Jan 11, 2022 at 1:07 AM Les Ginsberg (ginsberg) < > [email protected]> wrote: > >>>>>> Robert - > >>>>>> > >>>>>> From: Robert Raszuk <[email protected]> > >>>>>> Sent: Monday, January 10, 2022 2:56 PM > >>>>>> To: Les Ginsberg (ginsberg) <[email protected]> > >>>>>> Cc: Tony Li <[email protected]>; Christian Hopps <[email protected]>; > Peter Psenak (ppsenak) <[email protected]>; Shraddha Hegde < > [email protected]>; Aijun Wang <[email protected]>; Hannes > Gredler <[email protected]>; lsr <[email protected]> > >>>>>> Subject: Re: [Lsr] BGP vs PUA/PULSE > >>>>>> > >>>>>> Les, > >>>>>> > >>>>>> We have received requests from real customers who both need to > summarize AND would like better response time to loss of reachability to > individual nodes. > >>>>>> > >>>>>> We all agree the request is legitimate. > >>>>>> > >>>>>> [LES:] It does not seem to me that everyone does agree on that – > but I appreciate that you agree. > >>>>>> > >>>>>> But do they realize that to practically employ what you are > proposing (new PDU flooding) requires 100% software upgrade to all IGP > nodes in the entire network ? Do they also realize that to effectively use > it requires data plane change (sure software but data plane code is not as > simple as PI) on all ingress PEs ? > >>>>>> > >>>>>> [LES:] As far as forwarding, as Peter has indicated, we have a POC > and it works fine. And there are many possible ways for implementations to > go. > >>>>>> It may or may not require 100% software upgrade – but I agree a > significant number of nodes have to be upgraded to at least support pulse > flooding. > >>>>>> > >>>>>> > >>>>>> And with scale requirements you are describing it seems this would > be 1000s of nodes (if not more). That's massive if compared to alternative > approaches to achieve the same or even better results. > >>>>>> > >>>>>> [LES:] Be happy to review other solutions if/when someone writes > them up. > >>>>>> I think what is overlooked in the discussion of other solutions is > that reachability info is provided by the IGP. If all the IGP advertises is > a summary then how would individual loss of reachability become known at > scale? > >>>>>> You seem focused on the notification delivery mechanism only. > >>>>>> > >>>>>> Les > >>>>>> > >>>>>> Many thx, > >>>>>> Robert > >>>>>> > >>>>>> _______________________________________________ > >>>>>> Lsr mailing list > >>>>>> [email protected] > >>>>>> https://www.ietf.org/mailman/listinfo/lsr > >>>>> > >>>> > >>> > >> > > > > _______________________________________________ > Lsr mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/lsr > -- <http://www.verizon.com/> *Gyan Mishra* *Network Solutions A**rchitect * *Email [email protected] <[email protected]>* *M 301 502-1347*
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