Go to the previous, next chapter.
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 (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.
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:
a person's email address on a computer: firstname.lastname@example.org a computer's name: somewhere.domain
The user portion is usually the person's account name on the system, though it doesn't have to be. somewhere.domain tells you the name of a system or location, and what kind of organization it is. The trailing domain is often one of the following:
Each country also has its own top-level domain. For example, the
us domain includes each of the fifty states. Other countries
represented with domains include:
The proper terminology for a site's domain name (somewhere.domain above) is its 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 mit.edu; similarly, Apple Computer's domain name is apple.com. While such obvious names are usually the norm, there are the occasional exceptions that are ambiguous enough to mislead---like 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.
actually a 32-bit number, but is most commonly represented as four
numbers joined by periods (.), like
This is sometimes also called a 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
192) is called an
``octet,'' representing one of four sets of eight bits. The first two
or three pieces (e.g.
192.55.239) represent the network that a
system is on, called its subnet. For example, all of the
computers for Wesleyan University are in the subnet
They can have numbers like
up to 65 thousand possible combinations (possible computers).
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
email@example.com) or via regular mail.
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 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
foosun.bar.com, the resolver knows
that it should ask the system
foovax.bar.com about systems in
bar.com. It asks what Internet address
has; if the name
foosun.bar.com really exists,
will send back its number. All of this ``magic'' happens behind the
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.
The actual connections between the various networks take a variety of forms. The most prevalent for Internet links are 56k leased lines (dedicated telephone lines carrying 56kilobit-per-second connections) and T1 links (special phone lines with 1Mbps connections). Also installed are T3 links, acting as backbones between major locations to carry a massive 45Mbps load of traffic.
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 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 section The Networks, the connections are of the 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'' Byron, Churchill's Grave @end flushright