Hi, Tony:
Yes, we should find the least cost to solve the problem. The mentioned failure prefixes/loopback will only be advertised under some conditions. The ABR should have such controls, as described in https://datatracker.ietf.org/doc/html/draft-wang-lsr-prefix-unreachable-annoucement-07#section-7 Best Regards Aijun Wang China Telecom From: [email protected] <[email protected]> On Behalf Of Tony Li Sent: Thursday, October 14, 2021 1:51 PM To: Les Ginsberg (ginsberg) <[email protected]> Cc: lsr <[email protected]>; Gyan Mishra <[email protected]> Subject: Re: [Lsr] "Prefix Unreachable Announcement" and "IS-IS and OSPF Extension for Event Notification" 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] <mailto:[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 -- <http://www.verizon.com/> <~WRD0000.jpg> Gyan Mishra Network Solutions Architect Email [email protected] <mailto:[email protected]> M 301 502-1347
_______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
