Hi Henk,
> It's not so clear to me, sorry. > Does anyone have an example (link or jpg) of a (sensible) topology > that would not work with multiple levels of hierarchy, but works > nicely/better with area-proxies (or FRs) ? Just curious. Certainly. Draw a 3x3 grid with nodes at each intersection. Replace each node with an L1 area. Image: https://upload.wikimedia.org/wikipedia/commons/0/0f/Figure_11-_a_three_by_three_grid.png >> The structure of legacy >> IS-IS areas effectively precludes a scalable network for using lower >> levels for transit. This constrains ISPs to ‘cauliflower’ topology >> where you have L1 on the outside, L2 just inside of L1, L3 inside of >> L2, etc. > > I understand. L1-8 forces a hierarchical network designs. > But even if one would have the tools to design a non-hierarchical > network, that doesn't mean one should do so. :-) Hierarchical abstraction is a fine thing, but traffic cannot be constrained to be hierarchical. Doing so forces the top of the hierarchy to have capacity that is greater than lower levels. Pragmatically, we can’t build things that have infinite capacity, so we have to make do with finite sized switching elements. Fortunately Clos taught us how to do this. :-) The result is that we need to have transit areas. > If there are spots in the network where the hierarchical constraints > are a problem in the real world, indeed it would be nice to have tools > like area-proxies in the tool-set, to help solve those problems. > > I would like to have both tools. > I think you do too (as you are author of both drafts). I concur. Tony _______________________________________________ Lsr mailing list Lsr@ietf.org https://www.ietf.org/mailman/listinfo/lsr
