Zen and the Art of Internet | Page 6

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 mail at your site.
A person sending the author mail would probably do something like this:
% mail [email protected] Subject: print job's stuck
I typed `print babe.gif' and it didn't work! Why??
The next time the author checked his mail, he would see it listed in his mailbox as:
% mail "/usr/spool/mail/brendan": 1 messages 1 new 1 unread U 1 [email protected] Tue May 5 20:36 29/956 print job's stuck ?
which gives information on the sender of the email, when it was sent, and the subject of the message. He would probably use the reply command of Unix mail to send this response:
? r To: joeuser@@foo.widener.edu Subject: Re: print job's stuck
You shouldn't print binary files like GIFs to a printer!
Brendan
Try sending yourself mail a few times, to get used to your system's mailer. It'll save a lot of wasted aspirin for both you and your system administrator.
Anatomy of a Mail Header
An electronic mail message has a specific structure to it that's common across every type of computer system. {The standard