@c -*-tex-*-
@node Basics
@chapter Network Basics
@menu
@end menu

We are truly in an information society.  Now more than ever, moving
vast amounts of information quickly across great distances is one of our
most pressing needs.  From small one-person entrepreneurial efforts,
to the largest of corporations, more and more professional people are
discovering that the only way to be successful in the '90s and beyond
is to realize that technology is advancing at a break-neck pace---and
they must somehow keep up.  Likewise, researchers from all corners of
the earth are finding that their work thrives in a networked
environment.  Immediate access to the work of colleagues and a
``virtual'' library of millions of volumes and thousands of papers
affords them the ability to encorporate a body of knowledge heretofore
unthinkable.  Work groups can now conduct interactive conferences with
each other, paying no heed to physical location---the
possibilities are endless.

You have at your fingertips the ability to talk in ``real-time''
with someone in Japan, send a 2,000-word short story to a group
of people who will critique it for the sheer pleasure of doing so, see
if a Macintosh sitting in a lab in Canada is turned on, and find out
if someone happens to be sitting in front of their computer
(@dfn{logged on}) in Australia, all inside of thirty minutes.  No
airline (or tardis, for that matter) could ever match that travel
itinerary.

The largest problem people face when first using a network is grasping
all that's available.  Even seasoned users find themselves surprised
when they discover a new service or feature that they'd never known
even existed.  Once acquainted with the terminology and sufficiently
comfortable with making occasional mistakes, the learning process will
drastically speed up.

@node Domains, IP Numbers, Basics, Basics
@section Domains
@cindex domains

Getting where you want to go can often be one of the more difficult
aspects of using networks.  The variety of ways that places are named
will probably leave a blank stare on your face at first.  Don't fret;
there is a method to this apparent madness.

If someone were to ask for a home address, they would probably expect
a street, apartment, city, state, and zip code.  That's all the
information the post office needs to deliver mail in a reasonably
speedy fashion.  Likewise, computer addresses have a structure to
them.  The general form is:

@smallexample
@var{a person's email address on a computer:} user@@somewhere.domain
@var{a computer's name:} somewhere.domain
@end smallexample

The @var{user} portion is usually the person's account name on the
system, though it doesn't have to be.  @var{somewhere.domain} tells
you the name of a system or location, and what kind of organization it
is. The trailing @var{domain} is often one of the following:

@table @code
@item com
Usually a company or other commercial institution or organization,
like Convex Computers (@samp{convex.com}).

@item edu
An educational institution, e.g@. New York University, named @samp{nyu.edu}.

@item gov
A government site; for example, NASA is @samp{nasa.gov}.

@item mil
A military site, like the Air Force (@samp{af.mil}).

@item net
Gateways and other administrative hosts for a
network (it does @emph{not} mean all of the hosts in a
network).@footnote{@cite{The Matrix}, 111.}  One such gateway is
@samp{near.net}.

@item org
@cindex EFF (Electronic Frontier Foundation)
This is a domain reserved for private organizations, who don't
comfortably fit in the other classes of domains.  One example is the
Electronic Frontier Foundation (@pxref{EFF}), named @samp{eff.org}.
@end table

Each country also has its own top-level domain.  For example, the
@code{us} domain includes each of the fifty states.  Other countries
represented with domains include:

@table @code
@item au
Australia
@item ca
Canada
@item fr
France
@item uk
The United Kingdom.  These also have sub-domains of things like
@samp{ac.uk} for academic sites and @samp{co.uk} for commercial ones.
@end table

@c @cindex FQDN (Fully Qualified Domain Name)
@cindex FQDN
The proper terminology for a site's domain name
(@var{somewhere.domain} above) is its @dfn{Fully Qualified Domain
Name} (FQDN).  It is usually selected to give a clear indication of
the site's organization or sponsoring agent.  For example, the
Massachusetts Institute of Technology's FQDN is @samp{mit.edu};
similarly, Apple Computer's domain name is @samp{apple.com}.  While
such obvious names are usually the norm, there are the occasional
exceptions that are ambiguous enough to mislead---like @samp{vt.edu},
which on first impulse one might surmise is an educational institution
of some sort in Vermont; not so.  It's actually the domain name for
Virginia Tech.  In most cases it's relatively easy to glean the
meaning of a domain name---such confusion is far from the norm.

@node IP Numbers, Resolving, Domains, Basics
@section Internet Numbers
@cindex Internet number
@cindex address, IP (Internet)

Every single machine on the Internet has a unique address,@footnote{At
least one address, possibly two or even three---but we won't go into
that.} called its @dfn{Internet number} or @dfn{IP Address}.  It's
actually a 32-bit number, but is most commonly represented as four
numbers joined by periods (@samp{.}), like @code{147.31.254.130}.
This is sometimes also called a @dfn{dotted quad}; there are literally
thousands of different possible dotted quads.  The ARPAnet (the mother
to today's Internet) originally only had the capacity to have up to
256 systems on it because of the way each system was addressed.  In
the early eighties, it became clear that things would fast outgrow
such a small limit; the 32-bit addressing method was born, freeing
thousands of host numbers.

Each piece of an Internet address (like @code{192}) is called an
``octet,'' representing one of four sets of eight bits.  The first two
or three pieces (e.g. @code{192.55.239}) represent the network that a
system is on, called its @dfn{subnet}.  For example, all of the
computers for Wesleyan University are in the subnet @code{129.133}.
They can have numbers like @code{129.133.10.10}, @code{129.133.230.19},
up to 65 thousand possible combinations (possible computers).
@cindex octet
@cindex subnet

IP addresses and domain names aren't assigned arbitrarily---that would
lead to unbelievable confusion.  An application must be filed with the
Network Information Center (NIC), either electronically (to
@code{hostmaster@@nic.ddn.mil}) or via regular mail.

@node Resolving, Types, IP Numbers, Basics
@section Resolving Names and Numbers
@cindex resolving
Ok, computers can be referred to by either their FQDN or their
Internet address.  How can one user be expected to remember them all?

They aren't.  The Internet is designed so that one can use either
method.  Since humans find it much more natural to deal with words
than numbers in most cases, the FQDN for each host is mapped to its
Internet number.  Each domain is @dfn{served} by a computer within
that domain, which provides all of the necessary information to go
from a domain name to an IP address, and vice-versa.  For example,
when someone refers to @code{foosun.bar.com}, the @dfn{resolver} knows
that it should ask the system @code{foovax.bar.com} about systems in
@code{bar.com}.  It asks what Internet address @code{foosun.bar.com}
has; if the name @code{foosun.bar.com} really exists, @code{foovax}
will send back its number.  All of this ``magic'' happens behind the
scenes.
@cindex address, IP (Internet)
@c @cindex FQDN (Fully Qualified Domain Name)
@cindex FQDN

Rarely will a user have to remember the Internet number of a site
(although often you'll catch yourself remembering an apparently
obscure number, simply because you've accessed the system frequently).
However, you will remember a substantial number of
FQDNs.  It will eventually reach a point when you are able to make a
reasonably accurate guess at what domain name a certain college,
university, or company might have, given just their name.

@node The Networks
@section The Networks
@menu
@end menu

@table @dfn
@itemx Internet
The Internet is a large ``network of networks.''  There is no
one network known as The Internet; rather, regional nets like SuraNet,
PrepNet, NearNet, et al., are all inter-connected
(nay, ``inter-networked'') together into one great living thing,
communicating at amazing speeds with the TCP/IP protocol.  All
activity takes place in ``real-time.''

@itemx UUCP
@c @cindex UUCP (Unix-to-Unix Copy Program)
@cindex UUCP
The UUCP network is a loose association of systems all communicating
with the @samp{UUCP} protocol.  (UUCP stands for `Unix-to-Unix Copy
Program'.)  It's based on two systems connecting to each other at
specified intervals, called @dfn{polling}, and executing any work
scheduled for either of them.  Historically most UUCP was done with
Unix equipment, although the software's since been implemented on
other platforms (e.g. VMS).  For example, the system @var{oregano}
polls the system @var{basil} once every two hours.  If there's any
mail waiting for @var{oregano}, @var{basil} will send it at that time;
likewise, @var{oregano} will at that time send any jobs waiting for
@var{basil}.

@itemx BITNET
@cindex BITNET
@cindex NJE protocol, for BITNET
BITNET (the ``Because It's Time Network'') is comprised of systems
connected by @dfn{point-to-point} links, all running the NJE protocol.
It's continued to grow, but has found itself suffering at the hands of
the falling costs of Internet connections.  Also, a number of mail
gateways are in place to reach users on other networks.
@end table

@node The Physical Connection
@section The Physical Connection

The actual connections between the various networks take a variety of
forms.  The most prevalent for Internet links are @dfn{56k leased
lines} (dedicated telephone lines carrying 56kilobit-per-second
connections) and @dfn{T1 links} (special phone lines with 1Mbps
connections).  Also installed are @dfn{T3 links}, acting as backbones
between major locations to carry a massive 45Mbps load of traffic.
@cindex leased line

@cindex SLIP links, modem-based IP
These links are paid for by each institution to a local carrier (for
example, Bell Atlantic owns PrepNet, the main provider in
Pennsylvania).  Also available are @dfn{SLIP} connections, which carry
Internet traffic (packets) over high-speed modems.

UUCP links are made with modems (for the most part), that run from
1200 baud all the way up to as high as 38.4Kbps.  As was mentioned in
@ref{The Networks}, the connections are of the @dfn{store-and-forward}
variety.  Also in use are Internet-based UUCP links (as if things
weren't already confusing enough!).  The systems do their UUCP traffic
over TCP/IP connections, which give the UUCP-based network some
blindingly fast ``hops,'' resulting in better connectivity for the
network as a whole.  UUCP connections first became popular in the
1970's, and have remained in wide-spread use ever since.  Only with
UUCP can Joe Smith correspond with someone across the country or
around the world, for the price of a local telephone call.

BITNET links mostly take the form of 9600bps modems connected from site
to site.  Often places have three or more links going; the majority,
however, look to ``upstream'' sites for their sole link to the network.

@vskip 0pt plus 1filll
@flushright
``The Glory and the Nothing of a Name''
@b{Byron}, @cite{Churchill's Grave}
@end flushright
