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Re: pretty cool paper re "myth of Internet growth numbers"

  • From: Sean Donelan
  • Date: Sat Dec 02 22:25:11 2000

On Sat, 02 December 2000, k claffy wrote:
> [meta-operational content warning. 
> followup thread probably belongs on some other list]
> andrew odlyzko's latest

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

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.