In article <200005141743.e4EHheW09551@sss1.gwi.net>, Fletcher E Kittredge <fkittred@sss1.gwi.net> wrote:
http://smg.ulb.ac.be/Preprints/Fortz99_29.html
mentions it was in Infocon 2000...
And oh, yes, most definitely worth the read.
A very interesting paper, but it does have a key assumption that may limit its applicability: "The above definition of the general routing problem is equivalent to the one used e.g. in Awduche et al. Its most controversial feature is the assumption that we have an estimate of a demand matrix." The approach laid out by Fortz and Thorup is very pleasant in its ability to show that a simple weight-based model can come close to optimal traffic engineering. But without any way to quantify how accurate our estimate of the demand matrix is, we cannot know whether the projected weights are actually even close to optimal. And considering the elasticity of demand, I would argue that an accurate demand matrix cannot be constructed for most Internet backbones given currently available tools and understanding. I would be happy to be wrong about this. -- Shields.
On 15 May 2000, Michael Shields wrote:
The approach laid out by Fortz and Thorup is very pleasant in its ability to show that a simple weight-based model can come close to optimal traffic engineering. But without any way to quantify how accurate our estimate of the demand matrix is, we cannot know whether the projected weights are actually even close to optimal. And considering the elasticity of demand, I would argue that an accurate demand matrix cannot be constructed for most Internet backbones given currently available tools and understanding.
Most. Not all. At some promising local ISP's in the Fairfax, VA, area, there were actually fairly good demand matrix data available. The macroflows due to the architecture employed were actually fairly tractable and if one were to use ordinal (good enough) vs cardinal (best possible) optimization techniques[1], resulted in fairly usable parameters. The said parameters were useful for plugging into the traffic engineering tools du jour (SPVC contracts at the time). These data were also used to great effect in doing surviability analysis and circuit planning. [1] Overview of Ordinal Optimization, Dr. Yu-Chi Ho. Proceedings of the 33rd Conference on Decision and Control. /vijay
participants (2)
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Michael Shields -
Vijay Gill