I'm forwarding this for Paul, who's on vacation...
FYI for anyone interested in something to give customers or management 
Blurb follows.
Avi
[snip]
Here is a pointer to the completed white paper that Geoff
Huston (Telstra Internet) and I have just completed:
Title: What is a VPN?
Abstract:
The term "VPN," or Virtual Private Network, has become almost as
recklessly used in the networking industry as has "QoS" (Quality
of Service) to describe a broad set of problems and "solutions,"
when the objectives themselves have not been properly articulated.
This confusion has resulted in a situation where the popular trade
press, industry pundits, and vendors and consumers of networking
technologies alike, generally use the term "VPN" as an offhand
reference for a set of different technologies. This paper attempts
to provide a common sense definition of a VPN, and an overview of
different approaches to building them.
The paper can be found under the subheading "Presentations, Slideware,
and Assorted Cruft" at the URL:
  http://www.employees.org:80/~ferguson/
This paper is currently only available in a PostScript (.ps) and
Adobe Acrobat (.pdf) formats.
The paper (filenames: vpn.zip & vpn.pdf) is also available via anonymous
ftp at ftp://ftp.employees.org/ferguson/<filename>
It should be noted that this is not a positioning paper, but
rather, an attempt to provide some sanity in the effort to
define what constitutes a virtual private network.
Please direct any comments, concerns, kudos, etc. to either Geoff
or myself directly.
Cheers,
- paul (on vacation)
[snip]