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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Geographic v. topological address allocation
Vadim Antonov <[email protected]> writes: > Sean Doran wrote: > > > As tli pointed out the top of the hierarchy is not > > arbitrary, it must be default free. > > Sorry for the nitpicking, but this definition has at least two > flaws: > > a) there's a bi-partite backbone configuration, where each half > has default pointing to the other half. Both do not have to > carry full routes. (Of course, this scheme has problems with > packets destined to the blue, or can be extended to more than > two partitions). In effect, this entails the synthesis by equivalent areas of a superior level into which each party can default. I touched on this briefly in my previous message. With variable length addressing this kind of joint level-n-plus-one synthesis is easy; the new area simply encompasses sufficient bits to distinguish each level-n/level-n-plus-one IS participating in it. > b) multihomed non-transit networks may want to be default-free > and carry full routing to improve load sharing of outgoing > traffic. Since they are non-transit, they cannot be considered > "top of hierarchy". Yes, I believe I also mentioned Yakov's "pull" (did you see his slides at the IETF (and NANOG?) with which he presented his push/pull definitions?) can be used to optimize routing when strict hierarchical routing is inefficient. > Bingo. We are in sync, Vadim. Surprise surprise. Sean. P.S.: > Note that IXPs are not "top" of the hierarchy, but just > aggregators for essentially point-to-point links between > tier-1 backbones. This is a good way of putting it. I will steal it and use it myself from time to time.
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