> Of David Sinn > Sent: Wednesday, June 27, 2018 7:55 PM > > > > On Jun 27, 2018, at 8:40 AM, Thomas Bellman <bell...@nsc.liu.se> wrote: > > > > On 2018-06-26 21:38, David Sinn wrote: > > > >> OSPF scales well to many multiples of 1000's of devices. > > > > Is that true even for Clos (spine & leaf) networks, and in a single area? > > Yes for multi-tiered Clos, as that was the original ask and where my reference > is coming from. However, it is not in a single area. But if you are doing a > multi-tiered then the areas can fall out fairly naturally from the topology. > > > My understanding, solely based on what others have told me, is that > > the flooding of LSAs in a Clos network can start to overwhelm routers > > already at a few hundred devices, as each time e.g. a spine sends out > > an LSA, all of the other spines will hear that from each of the > > leaves, all more or less simultaneously. And since the OSPF protocol > > limits lifetimes of LSAs to 1 hour, you will get a constant stream of updates. > > Even Quagga/FRR has some measure of skew in the refresh interval to insure > that the re-advertisements aren't all clumped into one batch of updates from > a given node. And even having a really bad day where you loose power to a > good number of devices that basically all start up at the same time doesn't > cause measure-able congruence of updates. The skew in type-1's as the > boxes randomly bring up adjacencies and re-advertise their reachability gives > you a good spread across the refreshes over time which generally grows over > time. So while there is a continual background, even a single core PPC CPU's > on commodity boxes can handle it with multiple of the available white-box > OS's. > Haven't you guys heard of DNA LSAs to get rid of the flooding? -this is de facto standard in SP core networks. Also if you are having troubles keeping a reasonable number of IGP routes there's the hiding of transit-only networks RFC 6860 (all you really need are just the RIDs)?
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