Les, *I was just trying to illustrate that prefixes covered by the summary could > be advertised using existing IGP advertisements even when the summary is > being advertised. **It is still reachability. The determination of when > to advertise the prefix and when not to is still based upon whether the ABR > has a path to the prefix based on latest SPF calculation.* > > > > *You choose to rename such an advertisement as “liveness” rather than > “reachability” for no reason that I can see. It then allows you claim an > “architectural violation” – but this to me is a meaningless distraction. **I > was hoping to get rid of this distraction – but no such luck I see.* >
You are correct that from ABR it may look like atomic reachability. But if you look at the bigger picture what triggers this reachability is liveness detection between P and PE routers. And I guess what really matters is not how we call it - what matters is what truly triggers our protocol actions. *[LES:] This wasn’t the point of the example. I wasn’t promoting the > example as desirable deployment choice. I was only illustrating that it is > the change in reachability(sic) that is the event. With current IGP > advertisements we would (of course) stop advertising reachability when we > do not have a path to a given prefix. The new advertisements propose to > advertise the loss of reachability to destinations which are covered by a > summary. That has advantages over a withdrawal (the absence of an > advertisement).* > Perhaps. But it also has huge complexity on the clients (src PEs) which now need to bend to use this info. Something which is not in RIB disappears. I recall when you worked on RIB architecture one of the basic primitives was to always communicate protocol to protocol via RIB. Here we are talking about some not so elegant shortcuts. And not only in respect to protocols. Also touching FIB. It is perhaps the vendor's secret sauce how you use this new info. But by all means this is not what is today well known operational monitoring practice. That is why the ephemeral nature of the proposed advertisements is IMO its disadvantage. Thank you, R. >
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