mirror of https://github.com/tLDP/LDP
85 lines
4.0 KiB
XML
85 lines
4.0 KiB
XML
<sect1 id="Connectivity-Devices">
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<title>Connectivity-Devices</title>
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<para>
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The network topologies above can use several types of connectivity devices.
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Some are required (such as hubs for star networks) and othes provide
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optional features; for example, a repeater can extend the length of a
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bus network segment.
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</para>
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<para><variablelist>
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<varlistentry><term>Repeaters</term><listitem><para>
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Repeaters connect network media to extend total length. The purpose of this
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device is to eliminate the effects if attenuation. However, as is outlined in
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the 'Overview' section of this document it can sometimes inadvertently add
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'noise' to the network signal. Please see the 'Overview' for further details
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on this device.
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</para></listitem></varlistentry>
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<varlistentry><term>Hub</term><listitem><para>
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Hubs connect nodes and network resources in a network to a central point in a
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star topology. It should be noted that the usage of these devices has largely
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been eliminated as the development of 'switch' and general 'switching-fabric'
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technology has delivered increased levels of speed and efficiency in network
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communication. Switches and routers are two types of hubs.
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</para></listitem></varlistentry>
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<varlistentry><term>Switch</term><listitem><para>
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Switches connect nodes in a private network to a central point in a star
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topology. They send packets to nodes based on MAC address and provide
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roughtly the same functionality as 'routers' but much more efficiently
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and on a different level.
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</para></listitem></varlistentry>
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<varlistentry><term>Bridge</term><listitem><para>
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Bridges filter and move data between segments based on MAC address.
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For example, an ethernet bridge is a device that controls data packets
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within a subnet in an attempt to cut down the amount of traffic. A bridge
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is usually placed between two separate groups of computers that talk
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within themselves, but not so much with the computers in the other group.
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A good example of this is to consider a cluster of Macintoshes and a
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cluster of Unix machines. Both of these groups of machines tend to be
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quite chatty amongst themselves, and the traffic they produce on the network
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causes collisions for the other machines who are trying to speak to one
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another. A bridge would be placed between these groups of computers. The
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job of the bridge is then to examine the destination of the data packets one
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at a time and decide whether or not to pass the packets to the other side of
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the ethernet segment. The result is a faster, quieter network with less
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collisions. Several bridges can work together to create even larger networks
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of Ethernets using the IEEE 802.1 spanning tree algorithm. As this is a
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standard, Linux bridges will interoperate properly with other third party
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bridge products. Additional packages allow filtering based on IP, IPX or MAC
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addresses. Please see the Bridge-HOWTO for further details as to their purpose,
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usage and implementation.
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</para></listitem></varlistentry>
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<varlistentry><term>Router</term><listitem><para>
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A special purpose computer, hardware device or software package that
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handles the connection between two or more packet-switched networks. Routers
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spend all their time looking at the logical source and logical destination
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addresses of the packets passing through them and deciding which route or
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host to send them on to. Please see the 'Routing' section for further details
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on this device.
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</para></listitem></varlistentry>
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<varlistentry><term>Brouter</term><listitem><para>
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A network device that combines bridge and router capablities.
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</para></listitem></varlistentry>
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<varlistentry><term>Gateway</term><listitem><para>
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The technical meaning is a hardware or software set-up that translates
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between two dissimilar protocols/data formats, for example America Online
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has a gateway that translates between its internal, proprietary e-mail
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format and Internet e-mail format. Another, sloppier meaning of gateway
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is to describe any mechanism for providing access to another system,
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e.g. AOL might be called a gateway to the Internet.
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</para></listitem></varlistentry>
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</variablelist></para>
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</sect1>
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