Les, If you’re advertising loopbacks that are outside of the summarized space, then you end up with reachability and liveness. Yes, there’s a cost in scalability… it ain’t free.
Tony > On Oct 13, 2021, at 10:36 PM, Les Ginsberg (ginsberg) <[email protected]> > wrote: > > Tony – > > Given that IGPs provide the ability to advertise summaries (in the interest > of scalability), I think it is reasonable to say that being able to advertise > reachability changes of endpoints covered by the summary also can be > considered as a legitimate use of the IGP. > IGPs certainly advertise reachability and do update those advertisements in > response to liveness changes. > So, I don’t agree w your conclusion that this isn’t logically a routing > protocol function. > > It is fair for you to think the solution is good or bad – happy to hear more > thoughts from you on that. But I don’t think arguing that the routing > protocol has no business being involved in this is on the mark. > > Les > > From: Lsr <[email protected] <mailto:[email protected]>> On Behalf Of > Tony Li > Sent: Wednesday, October 13, 2021 8:53 PM > To: Gyan Mishra <[email protected] <mailto:[email protected]>> > Cc: lsr <[email protected] <mailto:[email protected]>> > Subject: Re: [Lsr] "Prefix Unreachable Announcement" and "IS-IS and OSPF > Extension for Event Notification" > > > Hi Gyan, > > I fully understand the request. > > I still question whether it should be solved by routing. This is not a path > computation problem. It’s reachability and more significantly, liveness. > > That really seems like it’s looking for a slightly different architectural > tool. > > Yours in IS-IS, > Tony > > > > On Oct 13, 2021, at 6:04 PM, Gyan Mishra <[email protected] > <mailto:[email protected]>> wrote: > > > Hi Tony > > This is a real world problem for large scale networks where an service > providers core network is broken up into OSPF areas or ISIS levels and each > PEs loopback BGP next hop attribute for 1000s of PEs within an area are > summarized at the P router ASBR ISIS L1-2 router or OSPF ABR and the next hop > attribute loopback0 component prefix of the summary goes down. > > So we need a mechanism to signal via PUA or event notification mechanism that > the component went down that is part of the summary to force immediately > control plane convergence to avoid black hole of traffic during the failure. > > Kind Regards > > Gyan > On Wed, Oct 13, 2021 at 8:48 PM Tony Li <[email protected] > <mailto:[email protected]>> wrote: > > > Hi, > > > I’ve said it many times before, in many different venues: “BGP is not a dump > truck!”. > > Is the fact that I didn’t mention the IGPs taken as some indication that they > are fair game? > > No, the IGPs aren’t a dump truck either. > > We have a clear, unambiguous way of signaling individual system outages > already. You advertise a loopback address as a /32 or /128. > If your host goes down, the address is no longer routable. Done. > > If this technique is not sufficient, then perhaps it doesn’t belong in > routing. > > Tony > > _______________________________________________ > Lsr mailing list > [email protected] <mailto:[email protected]> > https://www.ietf.org/mailman/listinfo/lsr > <https://www.ietf.org/mailman/listinfo/lsr> > -- > <~WRD0000.jpg> <http://www.verizon.com/> > Gyan Mishra > Network Solutions Architect > Email [email protected] <mailto:[email protected]> > M 301 502-1347 > > >
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