Paul, While I am still waiting for you to convince me, that DV is superior to Dijkstra, let me expand on the 10x10 chessboard grid example where you have 184758 shortest path from the left upper corner A to the right lower corner B. Grab one of them! Then envision that each of its 20 best next hops might be replaced by a 3-hops-detour: 1 hop to some more remote node, followed by 2 (explicitly enforced) best next hops, where each of which must not go back to where the packet come from.So there will be "20 over 1" = 20 paths with just one such detour. Additionally there will be "20 over 2" paths with 2 such detours, etc. etc. Altogether there will be 2^20 = 1048576 paths which include 0,1,2,...19 or 20 such detours. 184758 x 1048576 =193,730,707,456. I.e.by enabling such little obviously smallest possible detours there are 193,730,707,456 paths from A to B. No comes the worst: With DV you won't get to know that any such detouring path exists !! You have no rearview mirror. DV restricts the number of routes enormously and prevents traffic engineering which deserves its name. Heiner In einer eMail vom 14.02.2010 21:11:21 Westeuropäische Normalzeit schreibt [email protected]:
In einer eMail vom 14.02.2010 17:00:37 Westeuropäische Normalzeit schreibt [email protected]: Hi, I've only just stumbled across your TARA stuff, and am reading through your mails. Re "Forget DV!", and double-plus to that! Well, then try to convince me while viewing the following: I was told that an average route contains about 20 hops. Imagine a chessboard like grid however with 10x10 rows and columns instead of 8x8. Imagine each DFZ-router has only 4 neighboring DFZ-routers (which is certainly less than in reality).Imagine the ingress at the upper left corner and the egress at the lower right corner. Then there are (20 over 10) = 20x19x...x11 / (1x2x3....x10) = 184 758 shortest paths in-between. Consider that there are more than 10,000 egress DFZ-routers ! 184 756 times 10 000 = 1 847 560 000 shortest routes. However there are multitudes thereof, if you envisioned (loopfree of course) detours as well! And if you envisioned that DFZ routers have more than 4 neighbor nodes (BTW, can anyone provide useful valid figures so that we can discuss density issues and aspects?) What a nonsense of algorithm !!! DV is a holy cow from the early 90's! Please convince me, why provisioning and managing all these routes would be reasonable? Particularly, when you can do it without! Heiner
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