248 lines
9.7 KiB
Plaintext
248 lines
9.7 KiB
Plaintext
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----------------------------------------------------------
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What The Fuck Series #1 : What The Fuck Is Network Cable ?
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By Yetzer_Ra
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The afternoon sun blazes down on the bamboo hut as you approach the door.
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Here is the home of the fabled Yetzer Ra. You approach with caution.
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"Ah Packethopper! You have come to ask of me the wisdom of networking cable!
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Come, Come inside! I see you have brought Bombay Sapphire with you. A wise
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student you are! Now come! In now!"
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"We shall begin!"
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Network cables. Those fun piles of snake like wire that pile up behind your
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desk, under your chair, or in piles in the garage after a good night of
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dumpster diving. Ahhh wire. That wonderful medium that carries the signal
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from computer to computer in the network. Pure bliss.
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What? You say you don't know how to tell one from another? What is this web
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like coppery stuff that breaks into shards and sticks in your fingers when you
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cut it with a steak knife? Well, packethopper, take off you shoes and have a
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seat on the rattan mat. We begin now.
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Networking cable is the physical media that carries the network signals from
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the computer to the rest of the universe - be that another computer, a hub,
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or so so on (See "What The Fuck Is Network Topology").
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This resides on the OSI model at the physical layer.
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Let's review the OSI model with our mantra ....
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"if Another Person Says The Network's Down Pummel them "
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What's this? You don't see the wisdom in this mantra? Allow me to demonstrate:
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if
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Application Another
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Presentation Person
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Session Says
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Transport The
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Network Networks
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Data Link Down
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Physical Pummel
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them
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Now then, while you make the rice, I will explain the different types of wire
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used in networking computers. While there are well over two thousand types of
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wire and cable, only three of them are generally used with computer networking.
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They are coaxial, Twisted Pair, and Fiber Optic. Hand me that bottle of Gin
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and I will explain them to you.
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COAXIAL
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__________________________
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The basic makeup of a coaxial cable consists of a core made of solid copper,
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surrounded by a insulation material, and a braided metal shielding. This
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entire package is covered with a further outer shield that is usually black
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in color. In effect it looks like this:
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Outer Cover -------|
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| |--------- Insulation
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\/ |
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__________________________________________ |
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\/
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Wire Mesh -------------> XXXXXXXXXXXXXXX
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'''''''''''''''''''''''''''''''''''''''''''''''''________
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`''''''''''''''''''''''''''''''''''''''''''''''''
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Wire Mesh --------------> XXXXXXXXXXXXXXX /\
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____________________________________________ |-------- Copper
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Core
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The core of the cable carries the signals on their life journey. This is
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composed of copper, and can be either solid or stranded depending on the type
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of cable that it is.
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Surrounding this is a insulation that prevents the conducting core from
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shorting out against the wire mesh. This insulation is composed of either
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PVC or Teflon.
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Surrounding this is a copper wire mesh, or a alumimum sleve, depending on the
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cable type. The purpose of this is to shield further the conducting core from
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stray electrical signals. This can be as little as one layer, or as much as
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two layers each of foil and braiding for extreme conditions.
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Finally this whole masterpiece is covered by an outer cover. This is usually
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a black resin that is stamped at a regular interval with they type of cable,
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maker's name, or other information. It is made of either rubber, teflon or
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plastic.
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So now that you have gleaned this pearl of wisdom, let us further look into
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the types of coaxial cable used for data transmission. They are referred to
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as Thinnet and Thicknet.
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Thinnet measures .25" thick, and is quite flexible. It has the ability to
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carry a signal 607 feet before the signal gives in to attenuation.
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Thicknet measures 0.5" thick, and has a thicker core than thinnet. Thicknet
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has the ability to carry a signal for 1,640 feet before the signal gives in
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to attenuation.
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"What? Your miserable voice is telling my ears that you do not grasp the
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concept of attenuation? Then listen to my words once more, and bring me
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some more ice and limes."
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As a signal travels down the cable, it begins to slowly degrade. This is a
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result of resistace inherent in the cable, and other factors (See "What The
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Fuck does V=I/R Mean ?")
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This can cause data to be garbled, lost, or errors to pop up in terribly
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inconvenient places. There are ways to extend this limitation, but that will
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be for another lesson (See "What The Fuck Is Network Topology").
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Now that we know what coax is composed of, I will show you the names and
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different types of coax that are in existance. At this point you may
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recognize some terms used, and enlightenment will follow.
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Cable Type Description
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_____________________________________________________________________
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RG-58/U Solid copper core
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RG-58 A/U Stranded wire core
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RG-58 C/U Military standard of RG-58 A/U
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RG-59 Cable Television
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RG-6 Larger in diameter than RG-59, and can handle
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higher frequencies.
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RG-62 ArcNet networks
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____________________________________________________________________
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Coaxial cable is made in two grades as well. These are PVC (Polyvinyl Chloride)
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and Plenum.
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PVC revers to the plastic used as insulation in the construction of the cable.
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While this makes for a more flexible cable, in the event of a fire, burning
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PVC insulation releases toxic gasses. Plenum grade refers to the false ceiling
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area common to most offices (and a lot of movies where crawlspace is a vehicle
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for transport, such as in SNEAKERS), where cable can be run. Fire codes in
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most buildings require that plenum grade cable ONLY can be used in these
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spaces. The disadvantage is that the cable is less flexible.
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Coaxial cable used in a networking enviroment uses a connector referred to as
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a "BNC" or British Naval Connector. This is a round plug with a interlocking
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fit that makes it difficult to come apart.
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In fact, it's more likely that you will pull the cable from the plug, than
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to pull two properly connected BNC plugs apart.
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"Ahhh, good work, packethopper, you have brought more Bombay Sapphire. Your
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wisdom grows in leaps and bounds."
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Now, let us discuss the next type of networking cable....
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TWISTED PAIR CABLE
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As the name might indicate twisted pair consists of two strands of wire
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twisted around each other. This comes in two flavors: Unshielded twisted
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pair (UTP) and shielded twisted pair (STP). All this means is that the
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pairs are separated from each other by extra shielding (STP), whereas in the
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other case, they are not (UTP).
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Why would one want to twist the wires? A question of good merit, packethopper.
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The twisting allows the cable to naturally cancel out interference from
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adjacent cables (Crosstalk), and other sources. Technically this is called
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phase cancellation. This however does not work with 100% success, thus
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calling for STP cable to help eliminate further interference if needed.
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Categories of UTP
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This is the most commonly used LAN cable, built to the 10BaseT specification.
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The maximum length of a run of UTP is 100 meters (328 feet). The number of
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pairs, and the number of twists per foot vary depending on the category of
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the cable. Be very careful packethopper.... like there are different
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qualities of Gin, there are different qualities of UTP.
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CATEGORY 1 ( Bathtub Gin )
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This is basically telephone cable. Good for voice but NOT data.
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CATEGORY 2 ( Gordons Gin )
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This consists of four twisted pairs of wire, and can handle up to 4 Mbps
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(Megabits per second) of data.
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CATEGORY 3 ( Beefeater Gin )
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This consists of 4 twisted pairs, with three twists per foot, and can handle
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10 Mbps.
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CATEGORY 4 ( Bombay Gin )
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This consists of four twisted pairs, and can handle up to 16 Mbps.
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CATEGORY 5 ( Bombay Sapphire Gin )
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This consists of four twisted pairs, and can handle up to 100 Mbps.
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UTP used in a networking environment uses a connecter referred to as a "RJ-45".
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It is similar to a standard telephone connector (RJ-11) however it is larger,
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and has the capacity to connect 8 wires (4 pairs), whereas the RJ-11 can only
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handle 2 pairs.
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In order to prevent near end crosstalk (NEXT), the RJ-45 is connected to the
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wires in a UTP in the following manner.
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The colors named are the standard colors in cat 5 UTP. ( EIA 568 )
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Pin Wire Color
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___________________________________
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1 White/Orange
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2 Orange
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3 White / Green
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4 Blue
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5 White / Blue
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6 Green
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7 White / Brown
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8 Brown
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"Ah, the sun goes down, and there is little Gin left. Time for one more
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lesson, packethopper. The lesson of fiber optic."
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Fiber optic cable is composed of a thin cylinder of glass, referred to as the
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core, surrounded by a concentric layer of glass, referred to as the cladding.
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In some cases the fibers can be made of plastic. Plastic is easier to install,
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but will not carry data as far.
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Data is transmitted by pulses of light. Because of the lack of attenuation
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and purity of the signal, fiber optic cable can support 100 Mbps for miles.
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A fiber optic cable consists of two strands in seperate jackets, terminating
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at two plugs, One for transmission and one for recieving. These are encased
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in individual jacketing, and then both are covered in kevlar.
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While fiber optic cable is a wonderous thing, it is much more diffucult to
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splice, and is quite expensive.
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"Ah, packethopper, the gin is empty, and your mind is full. Go now and
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meditate on the wisdom that you have learned. Return tomorrow with more gin."
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"You have done well, packethopper."
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"Bow to the cow on your way out."
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