Lixia, Excuse my minimal knowledge about transport layer and DNS (I only think to know a lot about routing). So I cannot say anything wrt to pages 7 & 8. Maybe GROBJ enables some progress ? Heiner In einer eMail vom 10.11.2009 15:44:38 Westeuropäische Normalzeit schreibt [email protected]:
On Nov 10, 2009, at 1:32 AM, [email protected] wrote: > In einer eMail vom 10.11.2009 08:04:50 Westeuropäische Normalzeit > schreibt [email protected]: > >> the presentation slides are at: >> http://www.nanog.org/meetings/nanog44/presentations/Wednesday/Zhang_Wed_N44.pdf >> > > Quote from these slides: > The problem: routing too flat > solution: add more hierarchies in addressing & routing > > Yes, but do hierarchies right. There have been multiple hierarchical > proposals which did the hierarchical aggregation in the wrong way. > What it takes is a "sliding hierarchy" as provided by TARA so that > each router is fairly in the middle of the hierarchy and never at > the very rim. > Analogy: Imagine a city map for Istanbul, Turkey, with a Western > part containing each single street and an Eastern part being a > highly aggregated road map for entire Asia. > > Or take Compact Routing studies which mentioned stretch factor > 17 !!! Hierarchy is by no means a reason to enforce a path which is > longer than the shortest one! Neither when being in the middle or at > the rim ("Istanbul"). > > How many hierarchical levels is the right number? Who says "the less > the better" is wrong. > > I have my doubts that the routing folks have a proper understanding > wrt hierarchies. > > Heiner Hi Heiner, a couple comments here. 1/ one needs to read this with the understanding of its context--the quote you picked reflected understanding 15 years back. the world has changes in significant ways since then We understand much better now too. 2/ most importantly, I was calling attention to Postel's comments on slides 7 & 8: these quotes were taken from the meeting minutes then: - “Transport layer ID is not an issue that we need be concerned with for now. Once we decide what to do for IP addresses, then transport people can easily figure out how they may use the address.” - “We must avoid circular dependencies; - “we must define a substrate of the system that can operate without DNS. ... - “we must not depend on DNS to bootstrap the core operation of the system” Personally I believe these design guidelines still hold true today. Lixia
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