Zen and the Art of Internet | Page 6

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 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.
``The Glory and the Nothing of a Name'' Byron, {Churchill's Grave}
----------- Electronic Mail
The desire to communicate is the essence of networking. People have always wanted to
correspond with each other in the fastest way possible, short of normal conversation.
Electronic mail (or email) is the most prevalent application of this in computer
networking. It allows people to write back and forth without having to spend much time

worrying about how the message actually gets delivered. As technology grows closer and
closer to being a common part of daily life, the need to understand the many ways it can
be utilized and how it works, at least to some level, is vital. part of daily life (as has been
evidenced by the ISDN effort, the need to understand the many ways it can be utilized
and how it works, at least to some level, is vital.
Email Addresses
Electronic mail is hinged around the concept of an address; the section on Networking
Basics made some reference to it while introducing domains. Your email address
provides all of the information required to get a message to you from anywhere in the
world. An address doesn't necessarily have to go to a human being. It could be an archive
server, {See Archive Servers, for a description.} a list of people, or even someone's
pocket pager. These cases are the exception to the norm---mail to most addresses is read
by human beings.
%@!.: Symbolic Cacophony
Email addresses usually appear in one of two forms---using the Internet format which
contains @, an ``at''-sign, or using the UUCP format which contains !, an exclamation
point, also called a ``bang.'' The latter of the two, UUCP ``bang'' paths, is more restrictive,
yet more clearly dictates how the mail will travel.
To reach Jim Morrison on the system south.america.org, one would address the mail as
[email protected]. But if Jim's account was on a UUCP site named brazil, then his
address would be brazil!jm. If it's possible (and one exists), try to use the Internet form of
an address; bang paths can fail if an intermediate site in the path happens to be down.
There is a growing trend for UUCP sites to register Internet domain names, to help
alleviate the problem of path failures.
Another symbol that enters the fray is %---it acts as an extra ``routing'' method. For
example, if the UUCP site dream is connected to south.america.org, but doesn't have an
Internet domain name of its own, a user debbie on dream can be reached by writing to the
address not smallexample!
debbie%[email protected]
The form is significant. This address says that the local system should first send the mail
to south.america.org. There the address debbie%dream will turn into debbie@dream,
which will hopefully be a valid address. Then south.america.org will handle getting the
mail to the host dream, where it will be delivered locally to debbie.
All of the intricacies of email addressing methods are fully covered in the book ``!%@@::
A Directory of Electronic Mail Addressing and Networks'' published by O'Reilly and
Associates, as part of their Nutshell Handbook series. It is a must for any active email
user. Write to [email protected] for ordering information.
Sending and Receiving Mail

We'll make one quick diversion from being OS-neuter here, to show you what it will look
like to send and receive a mail message on a Unix system. Check with your system
administrator for specific instructions related to