On Sat, 02 December 2000, k claffy wrote:

[meta-operational content warning. followup thread probably belongs on some other list]

andrew odlyzko's latest http://www.cisp.org/imp/november_2000/odlyzko/11_00odlyzko.htm

http://www.research.att.com/~amo/doc/high.network.cost.txt I think Andrew has some apples and oranges mixed together in some of his papers. For example, he compares the utilitization of telephone trunk circuits (33% busy) with corporate LANs (3-4% busy). But ignores the typical corporate PBX, which sits idle most of the night and weekend. I suspect if you compared the corporate LAN with the corporate PBX, the utilitization rates would be similar. And in most companies, the availability of good measurements for intra-PBX calling and intra-LAN usage would be hard to find. Of course, that would open the whole can of worms of why do companies buy their own PBX's instead of using Centrex service from the phone company? I also expect if you compare similar points on the circuit hierarchy, similar utilizations would appear. Inter-POP circuits would be similar to Inter-CO trunks. Circuits between providers would be overloaded in the same way. And even inter-continental circuits would be similar between voice and data. But worst of all Andrew uses the *average* utilization, which is a poor way to measure utilization of data networks. Even utilization is a bit of a red herring because different absolute bandwidths. Networks (voice or data) are not designed using average utilization. Instead most designers use some type of peak utilization (95%, Mother's Day, etc). So what happens when a network gets near its peak utilization? With the voice network you get more busy signals. With the data network you get slower transfers. He also states the the traditional phone network continues to be more reliable than the Internet, which in my experience is an artifact of how the statistics are collected. If I called United Airlines' reservation number this year, I would think the telephone network reliability was pretty bad too. Instead the telephone network doesn't include end-to-end reachability in its reliability. But Internet measures such as Keynote do include end-to-end reachability.