Wire Media: UTP Unshielded Twisted Pair (UTP) –Ordinary copper wire –Twisted several times per inch to reduce interference –Pair of wires needed for a complete electrical signal –Unshielded: nothing but plastic coating No protection from interference

Wire Media: UTP Unshielded Twisted Pair (UTP) –Business telephone wiring traditionally comes in 4-pair UTP wire bundles –Used in LAN wiring to use existing building wiring technology

Wire Propagation: RJ-45 RJ-45 connector terminates a UTP bundle –Slightly wider than RJ-11 residential connector –Width needed for 8 wires

Wire Media: UTP to the Desktop UTP –Dominant for line from desktop to first hub or switch –Inexpensive to buy and install –Rugged: can take punishment of office work –Easily 100 Mbps, 1 Gbps with careful insulation UTP First Hub or Switch

Wire Media: Optical Fiber Optical Fiber –Glass core, surrounding glass cladding –Light source turned on/off for 1/0 –Total internal reflection at boundary –Almost no attenuation Light Source Cladding Core Reflection

Wire Media: Optical Fiber Limited by Distortion –Light entering at different angles travels different distances (different number of reflections) –Called different modes –Light from successive bits becomes mixed over long distances Light Source

Wire Media: Optical Fiber Multimode Fiber –Wide core makes easy to splice (50 or 62 microns) –Many angles for rays (modes) –Short propagation distance (usually 200 m to 500 m) Light Source Mod B

Wire Media: Optical Fiber Single Mode Fiber –Narrow core difficult to splice (5 or 8 microns) –Only one angle for rays (one mode), so (almost) no distortion –Longer propagation distance (usually up to 2 km for LAN fiber, longer for long-distance fiber) –Narrow core makes fiber fragile and difficult to splice

Wire Media: Optical Fiber Optical Fiber –High speeds over long distances 200 m to 2 km –Costs more than UTP, but worth it on long runs –Good for all links between hubs and switches within and between buildings in a site network Optical Fiber

Wire Media: UTP and Optical Fiber The emerging pattern: UTP from first hub or switch to desk, Fiber everywhere else on site

Wire Media: Coax Coaxial Cable –Used in cable TV, VCRs –Central wire, external concentric cylinder –Outer conductor wrapped in PVC Screw-On Connector Inner Wire Outer Conductor Wrapped in PVC

Wire Media: Coaxial Cable Coaxial Cable –Installed widely today in old 10 Mbps Ethernet LANs –Not being used in new installations Optical fiber more cost-effective for long links UTP more cost-effective for desktop links