Sean, Since you have have chosen to ignore kc's "meta-operational content warning" 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

I feel entitled to respond. First of all, your comments all appear to be based on the paper you cite, namely http://www.research.att.com/~amo/doc/high.network.cost.txt This is an entirely different paper on a different subject. (Moreover, just like the article kc cites, it is just a short overview of more detailed papers.) It is sort of like kc saying "Sean's new-born son is cute," and my responding "But his two-year old daughter is ugly." Either statement may be right or wrong, but there is little connection between them. Second, concerning the substance of your criticism, 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 do stand by the analysis of my papers. I do indeed mix apples and oranges, but that is inevitable in this context. In my 1998 paper with Kerry Coffman, "The size and growth rate of the Internet," we even say, to justify our efforts, that "While we cannot avoid comparing apples to oranges, we try not to compare apples to orange trees." However, the issues are definitely complex, and outside the scope of this mailing list. I would love to discuss this in greater detail with you, given your extensive knowledge of networks, as I think I could learn from such a discussion, but I would propose that we follow kc's warning and take this to a different forum. How about doing this through private email exchange? We can invite any members of this list who are interested in this issue to alert either one of us, and we will either cc them on the messages (if there are just a few), or set up a general short-term mailing list for the discussion. Would that be acceptable? Third, you write: 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. You appear to miss the point of the work. The aim of the analysis was to demonstrate that data networks are designed for and used for different purposes than the voice network, and that the commonly held notion that packet networks are superior to switched voice networks because they utilize transmission facilities more efficiently is just false. I am certainly not suggesting that average utilizations should be used in designing networks of any sort. Again, there is much more that can be said on this topic, but should not be said on this list. 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. This is a debatable point which has been dealt with rather extensively on this list, so I will respond at greater length. I agree with much of what you say, but, lacking any good metric, still feel, based on my personal experience and other anecdotal evidence, that the claim about Internet's lower reliability is valid. As one bit of evidence, let me note that starting on Tuesday 12 days ago, and continuing through yesterday morning, my home connection (through a cable modem) was down each day from about 4:15 am to 5:30 am. The problem was finally fixed yesterday. (It's a long story having to do with the interaction of the VPN and the cable system.) Nothing like this has ever happened to me with voice phones, and this is definitely not the first problem of this nature. Having said all this, let me add that I do not think this in any way shows the superiority of the voice phone network to the Internet, any more than the higher utilization of transmission links does. I feel that reliability is often overrated, and that examples of cell phones as well as PC's running Windows show that people care more about other things. Andrew