51 lines
2.6 KiB
HTML
51 lines
2.6 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<TITLE>Multicast over TCP/IP HOWTO: The MBone.</TITLE>
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<H2><A NAME="sect-mbone"></A> <A NAME="s4">4. The MBone.</A></H2>
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<P>Using a new technology usually carries some advantages and disadvantages.
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The advantages of multicast are -I think- clear. The main disadvantage is
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that hundreds of hosts and, specially, routers don't support it yet. As a
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consequence, people who started working on multicast, bought new equipment,
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modified their operating systems, and built <EM>multicast islands</EM> in
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their local places. Then they discovered that it was difficult to
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communicate with people doing similar things because if only one of the
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routers between them didn't support multicast there was nothing to do...
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<P>The solution was clear: they decided to build a <EM>virtual multicast network</EM>
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in the top of the Internet. That is: sites with multicast routers between
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them could communicate directly. But sites joined across unicast routers would send
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their island's multicast traffic encapsulated in unicast packets to other
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multicast islands. Routers in the middle would not have problems, as they would
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be dealing with unicast traffic. Finally, in the receiving site, traffic would be
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de-encapsulated, and sent to the island in the original multicast way.
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Two ends converting from multicast to unicast, and then again to multicast
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define what is called a multicast <EM>tunnel</EM>.
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<P>The <EM>MBone</EM> or <EM>Multicast Backbone</EM> is that virtual multicast network
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based on multicast islands connected by multicast tunnels.
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<P>Several activities take place in the MBone daily, but it deserves to be
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remarked the profusion of tele-conferences with real time audio and video
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taking place across the whole Internet. As an example, it was recently
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transmitted (live) the talk Linus Torvalds gave to the Silicon Valley Linux
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Users Group.
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<P>For more information on the MBone, see:
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<P>
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<A HREF="http://www.mediadesign.co.at/newmedia/more/mbone-faq.html">http://www.mediadesign.co.at/newmedia/more/mbone-faq.html</A><P>
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