69 lines
2.9 KiB
HTML
69 lines
2.9 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.21">
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<TITLE> Modem-HOWTO: Two Modems (Modem Doubling)</TITLE>
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<LINK HREF="Modem-HOWTO-17.html" REL=next>
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<LINK HREF="Modem-HOWTO-15.html" REL=previous>
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<LINK HREF="Modem-HOWTO.html#toc16" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="Modem-HOWTO-17.html">Next</A>
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<A HREF="Modem-HOWTO-15.html">Previous</A>
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<A HREF="Modem-HOWTO.html#toc16">Contents</A>
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<HR>
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<H2><A NAME="s16">16.</A> <A HREF="Modem-HOWTO.html#toc16">Two Modems (Modem Doubling)</A></H2>
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<H2><A NAME="ss16.1">16.1</A> <A HREF="Modem-HOWTO.html#toc16.1">Introduction</A>
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</H2>
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<P> By using two modems at the same time, the flow of data can be
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doubled. It takes two modems and two phone lines. There are two
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methods of doing this. One is "modem bonding" where software at both
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ends of the modem-to-modem connection enables the paired modems to
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work like a single channel.</P>
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<P>The second method is called "modem teaming. Only one end of the
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connection uses software to make 2 different connections to the
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internet. Then when a file is to be downloaded, one modem gets the
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first half of the file. The second modems simultaneously gets the
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last half of the same file by pretending that it's resuming a download
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that was interrupted in the middle of the file. Is there any modem
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teaming support in Linux ??</P>
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<H2><A NAME="ss16.2">16.2</A> <A HREF="Modem-HOWTO.html#toc16.2">Modem Bonding</A>
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</H2>
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<P> There are two ways to do this in Linux: EQL and multilink. These
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are provided as part of the Linux kernel (provided they've been
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selected when the kernel was compiled). For multilink the kernel
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must be at least v.2.4. Both ends of the connection must run them.
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Few (if any) ISPs provide EQL but many provide Multilink.</P>
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<P>The way it works is something like multiplexing only it's the other
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way around. Thus it's called inverse-multiplexing. For the multilink
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case, suppose you're sending some packets. The first packet goes out on
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modem1 while the second packet is going out on modem2. Then the third
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packet follows the first packet on modem1. The forth packet goes on
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modem2, etc. To keep each modem busy, it may be necessary to send out
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more packets on one modem than the other. Since EQL is not packet
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based, it doesn't split up the flow on packet boundaries.</P>
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<H3>EQL</H3>
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<P>EQL is "serial line load balancing" which has been available for
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Linux since at least 1995. An old (1995) howto on it is in the kernel
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documentation (in the networking subdirectory). Unfortunately, ISPs
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don't seem to provide EQL.</P>
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<H3>Multilink</H3>
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<P> Staring with kernel 2.4 in 2000, experimental support is provided
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for multilink. It must be selected when compiling the kernel and it
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only works with PPP. </P>
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<HR>
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<A HREF="Modem-HOWTO-17.html">Next</A>
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<A HREF="Modem-HOWTO-15.html">Previous</A>
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<A HREF="Modem-HOWTO.html#toc16">Contents</A>
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