Hi Tony,
> Read it through (fairly slowly even ;-) and seems Les is for simply always > including LAN in the flood reduction topology. I would concur with that. Ok, I didn’t read that into it and I disagree. There are many topologies where that approach is decidedly suboptimal. Suppose you have a leaf-spine topology, except that the spines are layer 2 only. You now have N leaves, with M LANs interconnecting them. Do you flood in parallel on M LANs? Wouldn’t it be more prudent just to flood on 2? > figuring whether a LAN is transit is basically calculation whether it's a > minimal cut. solving that is polynomial of course. When we have multiple LANs > to decide what is the maximum subset of LANs that can be cut without > paritioning the graph (i.e. how many LANs can we omit while still having the > graph connected) smells to me NP complet'ish but I don't think I ever dealt > with the problem. At worst it's combination of LANs * polynomial computaton > so about sum_1_k (n over k) * polynomial which looks tad chewy to me ... > then, LAN floods efficiently in terms of fanout compared to p2p replication > in IGPs so there's this unknown optimization constant that affects overall > solution ... It’s pretty clear to me that the optimal selection of the FT is ‘chewy’ if not NP-hard. However, the very good news is that we don’t need optimal. Only effective and reasonably efficient. Dave Allan's proposal is a clear existence proof of a far less ‘chewy’ algorithm, albeit for a restricted set of topologies. Other algorithms are likely to be not very ‘chewy’ on those topologies either, and only become ‘chewy’ as the topologies get more complex. This seems entirely reasonable and appropriate. > Obvioulsy, someone could implement a very clever algorithm how to avoid LANs > or account for their efficiency and so on so IMO the draft doesn't even need > to say anything normative if no algorithm is given as intended AFAIR This is exactly correct. Since we are partitioning the algorithm development from signaling, we can set aside the question of how to optimally use LANs and focus on the question on the table: do we add enough signaling to specify LANs. Regards, Tony _______________________________________________ Lsr mailing list [email protected] https://www.ietf.org/mailman/listinfo/lsr
