This is a third attempt to respond to Tony Li via the rrg-mailinglist. Two preceding attempts were neither mirrored back nor included in the archive. I also try some rephrasing. Heiner In einer eMail vom 02.01.2010 20:57:52 Westeuropäische Normalzeit schreibt [email protected]:
Hi Heiner, > > Suppose that a geopatch has only a single TARA-router in it. It then > > becomes the decapsulator for all TARA traffic arriving into that > > geopatch. Who pays for this router? Who pays to deliver traffic > from > > this router to the destination access ISP? > > > > What is precisely the scenario ? You pressume that the > destination EID > > has a TARA-locator, being put into the DNS by some > non-TARA-router ????:-( > > > No, again, there's a single TARA-router. I'm interested in the > topology > and routing internal to the geopatch. This is the problematic area for > all geo-aggregation proposals. > > Note, this TARA model will yield stretch 1 !!! Only the process how to > acquire the flat TARA-map is somehow hierarchically organized. > > Whereas hierarchical topological models a la PNNI are bad - the > process itself, as well as the outcome. The Compact Routing studies > have shown how bad. I'm still not understanding your response to this key point. Indeed, this is a key point, and I hope you see that my kind of hierarchy is completely different to all the others. According to TARA there are 64800 hierarchies. On top ( and not at the bottom) of each of them, there is one particular geopatch with its internal topology. Then, in general, each of them is surrounded by 8 neighboring geopatches. These nine geopatches form a geopatch-cluster. A geopatch at the North (rsp. South) pole shall be part of a geopatch-cluster with adjacent geopatches 1 to the East, 1 to the West and 3 to the South (rsp. North). We may define (n,m) geopatch-clusters with n rows of m (=column) geopatches. Any (1,1)-geopatch might be part of some (3,3)-, (13,13)-,(37,37)-geopatch cluster and of course of the entire globe. I.e. 5 hierarchical layers might do. (and yet these figures are arbitrary and are for further study). And of course, these hierarchies do overlap. It takes a special kind of advertisement protocol to ensure that each with TARA enhanced BGP-router gets the proper (consistent ) set of strict/loose links. In this way the Istanbul effect can be avoided and at the same time we can afford that the protocol prescribes relatively small scale ratios to be applied when reduced/skimmed larger topologies are to be computed - as there are only 10 000 DFZ-routers altogether. Example: A geopatch'es (resp. geopatch-cluster's) topology contains 100 nodes and 250 links. Assume scale ratio = 1 : 5. Then the respectively skimmed network would comprise precisely 20 nodes and approximately 50 links, which will be its contribution to a (3,3) geopatch cluster. A proper advertisement protocol must take care that this information is exchanged across the borders, enabling a recursion of this process while being aware of the overlaps of geopatch clusters. Shortest patch computation will guarantee stretch-1 behavior instead of causing stretch-17 as Compact Routing experts emphasize in order to blame hierarchical concepts; well, their hierarchical concepts. Heiner
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