The examples used in this book are taken from my own experiences, as well as from
the experiences of those with or for whom I have had the pleasure of working. Of course,
for obvious legal and honorable reasons, the exact details and any information that
might reveal the identities of the other parties involved have been changed.
Cisco equipment is used for the examples within this book and, with very few exceptions,
the examples are TCP/IP-based. You may argue that a book of this type should
include examples using different protocols and equipment from a variety of vendors,
and, to a degree, that argument is valid. However, a book that aims to cover the breadth
of technologies contained herein, while also attempting to show examples of these
technologies from the point of view of different vendors, would be quite an impractical
size. The fact is that Cisco Systems (much to the chagrin of its competitors, I’m sure)
is the premier player in the networking arena. Likewise, TCP/IP is the protocol of the
Internet, and the protocol used by most networked devices. Is it the best protocol for
the job? Perhaps not, but it is the protocol in use today, so it’s what I’ve used in all my
examples. Not long ago, the Cisco CCIE exam still included Token Ring Source Route
Bridging, AppleTalk, and IPX. Those days are gone, however, indicating that even Cisco
understands that TCP/IP is where everyone is heading. I have included a chapter on
IPv6 in this edition, since it looks like we’re heading that way eventually.
WAN technology can include everything from dial-up modems (which, thankfully, are
becoming quite rare) to T1, DS3, SONET, MPLS, and so on. We will look at many of
these topics, but we will not delve too deeply into them, for they are the subject of entire
books unto themselves—some of which may already sit next to this one on your
O’Reilly bookshelf.
Again, all the examples used in this book are drawn from real experiences, most of
which I faced myself during my career as a networking engineer, consultant, manager,
and director. I have run my own company and have had the pleasure of working with
some of the best people in the industry. The solutions presented in these chapters are
the ones my teams and I discovered or learned about in the process of resolving the
issues we encountered.