Linux Networking Clearly Explained - lions-wing.net

CHAPTER 1 • CREATING A DIAL-UP INTERNET CONNECTION 7
designed to work with. You will learn much more about
protocols in this book, but here is a short definition—a
protocol is a standard that defines how computer devices
communicate with each other. Some protocols are proprietary;
that is, they are developed by a commercial vendor,
who regards them as a trade secret. Open protocols are
developed by trade industry groups that seek to enlarge
the market for everyone by agreeing on openly available
standards. Open protocols are generally ratified and
maintained by international standards organizations.
Public protocols are those developed with public funding
and released for public use, without restriction.
You want a 56 Kbps modem, but not just any 56 Kbps
modem. “Bargain-basement” modems may work only
with certain proprietary 56 Kbps protocols, such as X2,
that were offered before the current standard (V.90) was
ratified. Look for a modem that conforms to the V.90
protocol.
Hardware and Software Modems
Modems do more than serve as an intermediary between
the computer’s digital messaging and the telephone
system’s analog connections. They can also perform certain
additional tasks, such as compressing data for faster
transfer and checking for errors and correcting them automatically.
To perform these tasks, modems need guidance
from software. Most modems provide the needed software
by means of permanently encoded chips contained
within the modem’s hardware; these modems are called
hardware modems—and, as you will see, this is the type
of modem you want for your Linux system.