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    Networking Media

    The channel through which network signals flow. Examples: Air: microwaves.
    Glass fiber: light.
    Wire cabling: electrical signals.

    While each media has unique characteristics, all media provide the same functionality i.e. they permit information to move from one location to another.

    Three Primary Cable Types 

    Coaxial 
    Twisted pair (UTP or STP) 
    Fiber Optic 
    Wireless is used in niches where major cable types are not appropriate.  Expensive 
    Major Wireless Technologies  Microwave
    Infrared 
    Laser 
    Spread-spectrum radio 
    General Cable Characteristics   Bandwidth  Bits or bytes per unit time Max segment length   How long can the signal run? Max number of segments (Coax)  Latency measures the amount of time it takes for a signal to travel from one end of the cable to another.  Max number of devices per segment (Coax)   WEach device creates an insertion loss (signal attenuation).  Interference susceptibility   Each cable type has a unique susceptibility to EMI or RFI interference. Physical Connection    Each cable/NIC has a standard connectors.  Cost and attachment labor should be also considered. 

    Cable Characteristics  
    Bend radius -- Some cables can be damaged by bending  

    Certain fiber optic cables can only be bent 60 degrees per foot.
    Costs   Each cable has unique equipment, labor, and testing cost structures.
    Cable Grade  Dictated by building, fire codes, or the EIA/TIA. 
    For installation in dropped ceilings; or other building spaces, cables must be plenum-rated.
    Cables employed in other areas may utilize the more economical polyvinyl chloride (PVC) coating. 
    Plenum Rated Plenum is the space between the false and the real ceiling 
    Cables used in that space, not enclosed in a conduit, must be plenum-rated. 
    Typically Teflon coated. 
    Low combustibility and toxicity. 
    Two Signaling Techniques  Baseband or Broadband 
    In general, baseband carries a single digital signal at a time; whereas, broadband carries multiple signals at the same time. 

    Baseband 

    Baseband single carrier, single signal. A bi-directional digital encoding scheme at a fixed frequency. Signals take the form of discrete pulses. 
    WInterlinked by repeaters. 
    Broadband   Broadband single or dual carrier, multiple signals.
    An analog encoding scheme across a continuous range of values. 
    Interlinked by amplifiers. 
    Coaxial Cable  Single core conductor, surrounded by an insulating layer, then a braided metal shielding, and finally an outer cover. 
    Signal travels over the single core conductor. 
    Less susceptible to RFI, EMI and attenuation than twisted pair. 
    Three Cable Notation Methods   The Institute of Electrical and Electronics Engineers (IEEE) uses a three part notation to describe Ethernet cabling. 
    Cable manufacturers have designated Radio Government (RG) specifications for cables.  Each RG family has a characteristic impedance Unshielded Twisted Pair (UTP) is rated by the EIA/TIA 568 Commercial Building Wiring Standard. 
    IEEE Ethernet Notation  The first part represents the total bandwidth for the technology. In standard Ethernet, this is a 10.
    The second part indicates Baseband or broadband.  
    The third part originally indicated the max segment length. More recently, it has been used to refer to the media. 
    Coaxial Cable Applications  Thinnet Ethernet 
    RG 58 
    10base2
    Thicknet Ethernet 
    RG 8 
    10base5
    ArcNet 
    RG 62 
    10base4 (more or less) 
    10Base2 Ethernet Thin Ethernet, ThinNet, CheaperNet 
    Maximum Length of Segments: 185 meters (606.8 feet) 
    RG-58 A/U or RG-58 C/U Coaxial Cable  
    BNC Connectors 
    50 Ohm Impedance 
    Most economical form of coax  
    10Base5 Ethernet  Thick Ethernet, ThickNet 
    Maximum Length of Segments: 500 meters (1640 feet) unrepeated 
    RG-8/11Cable with external transceivers 
    N-type Connectors, Vampire Taps, DIX connectors 
    50-ohm impedance  
    Relatively expensive and difficult to work   
    10BaseT Ethernet  TWP, UTP, or Twisted Pair 
    Maximum Length of Segments: 100 meters (328 feet)  
    Cable: Data Grade Unshielded Twisted Pair (AT&T DIW Cable, Cat. 3, or 5)  
    RJ-45 Connectors
    If the cable is run through an air return use Plenum rated cable 
    Unshielded Twisted Pair Cable 
    Most popular form of LAN Cabling  Category 3 
    For up to 10 Mbs. 
    Four pairs of wire per cable.  Category 5 
    For up to 100 Mbs  
    UTP is vulnerable to crosstalk . Shielded Twisted Pair less so.

    Wiring Centers  

      TWP data networks, like telephone systems use wiring centers that have standard components. 
      Distribution racks, punchdown blocks and modular shelving help organize cables and permit them to be arranged vertically to conserve floor space.

    10BaseFB 

    Fiber Optic Cable 
    Maximum Length of Segments: 2000 meters (5,600 feet) 
    Cable: Typically 62.5/125 micron duplex FDDI compliant fiber optic cable 
    ST (Straight Tip) or SC (Straight Connection) connectors  
    Fiber Optic Cable Properties  Immune to EMI and RFI. 
    Cannot be tapped with conventional listening devices. 
    Depending on the technology, runs can be as long as 62 miles. 
    Takes special skills and tools to install.  
    General Cable Selection Criteria  Bandwidth  
    How fast does the network need to be? 
    Budget 
    How much money can be spent on cabling? 
    Capacity 
    How much traffic must the network carry? How will the traffic flow?  
    Specific Cable Selection Criteria  Environmental Considerations   Acceptable environment noise levels? Placement  Where will the cables be run? Scope  Number of connected devices  Span  What distance will the network span? Network Interface Cards