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<H2>Linux System Administrator's Survival Guide lsg13.htm</H2>



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<A HREF="#E68E71" >Choosing a Modem</A>



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<A HREF="#E68E72" >Installing a Modem</A>



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<A HREF="#E68E73" >Configuring a Modem</A>



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<A HREF="#E68E74" >Setting Fast Modem Speeds</A>



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<A HREF="#E68E75" >Summary</A></UL></UL></UL>



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<FONT SIZE=6 COLOR="#FF0000"><B>Chapter 13</B></FONT></CENTER></H1>



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<FONT SIZE=6 COLOR="#FF0000"><B>Modems</B></FONT></CENTER></H2>



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<P>If you want to talk to the outside world (a friend's computer, another network, the Internet, or a BBS, for example), or you want to let others talk to your Linux system, you need a modem. Modems used to be expensive, complex pieces of equipment that required a considerable amount of UNIX expertise to install and configure properly. Now, using one of today's highest speed modems is as easy as plugging it in and modifying a file or two. This short chapter looks at the installation requirements for a modem.



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<FONT SIZE=5 COLOR="#FF0000"><B>Choosing a Modem</B></FONT></CENTER></H3>



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<P>Linux works with just about any modem as long as it plugs into the system somehow and has a device driver. Choosing the modem then becomes a matter of using an existing modem on your PC or buying one specifically for Linux.



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<P>Modems are a competitive market. The fight between companies for the flashiest advertisements, most features, and best included software is leading to lower prices and better bargains. Most of the software included with modems is for DOS or Windows, you don't need to worry about any type of software for Linux. If you intend to run the modem on your DOS partitions, consider the software for that aspect only.



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<NOTE>As a general rule, if a modem works with DOS, it will work under Linux. When you install the modem, specify the serial port name, and Linux can work with the modem. A modem can work equally well with both operating systems.</NOTE>



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<P>A common problem in choosing from today's modems is the plethora of acronyms, speeds, and features that are touted for different modems. Modem standards have gone crazy in the last few years, as better telephone circuits (including fiberoptics) and more efficient data compression algorithms have been developed. Compression algorithms are the current fad in the market. They use sophisticated mathematical systems to pack as much as five times as many bits per second along a line. For this reason, everyone seems to want data compression in modems, but most users don't realize that the compression scheme must be identical on both ends of the line, or the default speed is the best a modem can achieve.



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<P>The current state-of-the-art modems use V.FC (V.Fast Class, also known as V.34), which has a speed of 28,800bps. V.FC modems are usually used with data compression schemes to boost the effective throughput to speeds as high as 115kbps. V.FC was developed as a project between Hayes Microcomputer Products and Rockwell. Over 100 modem manufacturers have agreed to accept it as a working standard. The V.34 standard has now been officially adopted. The same situation does not apply to some of the compression algorithms&#151;they are de facto, not actual standards. This point is probably moot as the sheer weight of the companies behind these modem standards should carry them through to adoption.



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<P>To help you keep up with the different modem speeds in use today, the following table lists the communications speeds (in bits per seconds) and their names.



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<TABLE  BORDERCOLOR=#000040 BORDER=1 CELLSPACING=2 WIDTH="100%" CELLPADDING=2 >



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Base communication speeds



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V.FC (V.Fast Class)



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28,800bps</FONT>



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V.34 / V.Fast)



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28,800bps</FONT>



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V.32terbo



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19,200bps</FONT>



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V.32bis



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14,400bps</FONT>



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V.32



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9,600bps</FONT>



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V.22bis



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2,400bps</FONT>



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212A



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1,200bps</FONT>



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V.21



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300bps</FONT>



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103



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300bps</FONT>



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Data compression systems



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V.42bis



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4:1 compression to 115,200bps on a 28,800bps line</FONT>



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MNP5



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2:1 compression algorithm used in older modems</FONT>



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Fax standards



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V.17



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14,400bps, 12,<A NAME="I2"></A>000bps, 9,600bps, and 7,200bps</FONT>



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V.29



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9,600bps and 7,200bps</FONT>



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