Networks

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Networks

• Physical Structure

2
ISO Model

• Seven layers
• Application Layer
• Presentation Layer
• Session Layer
• Transport Layer
• Network Layer
• Data Link Layer
• Physical Layer

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Cabling

• Types
• Copper
• Glass
• Plastic

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What is Network Cabling?

• Cable - medium through which information usually
  moves from one network device to another.
• Several types of cable are commonly used with
  LANs.

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What is Network Cabling?

• In some cases, a network will utilize only one
  type of cable other networks will use a variety
  of cable types.
• The type of cable chosen for a network is related
  to the network's topology, protocol, and size.
• Understanding the characteristics of different
  types of cable and how they relate to other
  aspects of a network is necessary for the
  development of a successful network.

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Cables

• Baseband (Copper)
• Signals are sent over the entire cable
• One digital frequency
• One device transmits at a time
• Broadband
• Cable is divided into channels
• Several analog signals
• Requires special equipment

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Baseband

• Speeds from 10 to 80 Mbs
• Easy to add / remove clients
• Bidirectional

• Distances 1.8 mile (3km)
• 1500 ft, 500 meters more realistic
• Cannot send integrated signals
• Audio, digital, video

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Broadband

• Carry multiple signals
• Commercial cable companies use 6mhz / channel
• Signals are sent to a Head End for
  amplification
• Unidirectional
• Dual Broadband Cable
• One cable for inbound traffic
• One cable for outbound traffic
• 50 channels (6Mhz) on each
• Lines need balancing and Amplifiers

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Multiplexing - mixing different frequencies Over
the same wire.
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Broadband Components

• Cable
• Trunk cables, feeder cables, drop cables
• 10s of kilometers, 800 meters, 10-50 feet
• Terminators 75 ohms
• Amplifiers
• Used on trunks to overcome attenuation (signal
  loss)
• Directional Couplers (splitters)
• Modems analog to digital conversion

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Data Quality Impacts

• Bandwidth of a cable
• How much of a signal can be carried (Mbps)
• Attenuation
• The loss of a signal due mostly to resistance
• Interference
• Bleeding of one signal over into another
• Electromagnetic, Radio Freq Interference,
  CrossTalk
• Motors / Broadcast station / Strong signal
  negates weaker

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Coaxial Cable

• Coaxial cabling has a single copper conductor at
  its center. A plastic layer provides insulation
  between the center conductor and a braided metal
  shield.The metal shield helps to block any
  outside interference from fluorescent lights,
  motors, and other computers.

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Coaxial Cable

• Although coaxial cabling is difficult to install,
  it is highly resistant to signal interference. In
  addition, it can support greater cable lengths
  between network devices than twisted pair cable.
  The two types of coaxial cabling are thick
  coaxial and thin coaxial.

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Coaxial Cable

• Thin coaxial cable is also referred to as thin
  net. 10Base2 refers to the specifications for
  thin coaxial cable carrying Ethernet signals. The
  2 refers to the approximate maximum segment
  length being 200 meters. In actual fact the
  maximum segment length is 185 meters. Thin
  coaxial cable is popular in school networks,
  especially linear bus networks.

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Coaxial Cable

• Coaxial cabling has a single copper conductor at
  its center. A plastic layer provides insulation
  between the center conductor and a braided metal
  shield.The metal shield helps to block any
  outside interference from fluorescent lights,
  motors, and other computers.

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Coaxial Cable

• Although coaxial cabling is difficult to install,
  it is highly resistant to signal interference. In
  addition, it can support greater cable lengths
  between network devices than twisted pair cable.
  The two types of coaxial cabling are thick
  coaxial and thin coaxial.

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Coaxial Cable

• Thin coaxial cable is also referred to as thin
  net. 10Base2 refers to the specifications for
  thin coaxial cable carrying Ethernet signals. The
  2 refers to the approximate maximum segment
  length being 200 meters. In actual fact the
  maximum segment length is 185 meters. Thin
  coaxial cable is popular in school networks,
  especially linear bus networks.

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Coaxial Cable

• Thick coaxial cable is also referred to as thick
  net. 10Base5 refers to the specifications for
  thick coaxial cable carrying Ethernet signals.
  The 5 refers to the maximum segment length being
  500 meters. Thick coaxial cable has an extra
  protective plastic cover that helps keep moisture
  away from the center conductor. Thick coaxial a
  great choice for longer lengths in a linear bus
  network. A disadvantage of thick coaxial is that
  it does not bend easily and is difficult to
  install.

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Coaxial Cable Connectors

• The most common type of connector used with
  coaxial cables is the Bayone-Neill-Concelman
  (BNC) connector. Different types of adapters are
  available for BNC connectors, including a
  T-connector, barrel connector, and terminator.
  Connectors on the cable are the weakest points in
  any network. To avoid problems with a network,
  always use the BNC connectors that crimp, rather
  than screw onto the cable.

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Copper Cables
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Copper Cables
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Twisted Pair (STP) Cable

• Twisted pair cabling comes in two varieties
  shielded and unshielded.
• Unshielded twisted pair (UTP) is the most popular
  and is generally the best option for school
  networks.
• A disadvantage of UTP is that it is susceptible
  to radio and electrical frequency interference.

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Twisted Pair (STP) Cable

• Shielded twisted pair (STP) is suitable for
  environments with electrical interference
  however, the extra shielding can make the cables
  quite bulky.
• Shielded twisted pair is often used on networks
  using Token Ring topology.

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Wiring pinouts

• TWISTED PAIR ETHERNET HORIZONTAL WIRING (Solid
  24Awg)
• Pin Color Signal 1 White/orange Tx data
  2 Orange/white Tx data - 3 White/green
  Rx data 4 Blue/white -- 5 White/Blue --
  6 Green/white Rx data - 7 White/brown --
  8 Brown/white -- Each run lt 80m from
  nearest hub

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Twisted Pair (STP and UTP)

• 10BaseT (Ethernet 10MB/s)
• Cheap
• easy to terminate
• UTP prone to interference
• low to medium capacity
• medium to high loss
• category 3 10MB/s, category 5 100MB/s
• Category 5 cable uses 8 wires. The length of
  exposed wires is very critical, the standard
  limits this to less than 1/2" an inch.

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10 8 6 4 2 .6 .4 .1
RG-59
RG-6
Attenuation db per 100ft
RG 11
.75 in Aluminum
8 12 16 20
40 60 80 100
200 300 400
Freq Mhz
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Cables-Twisted Pair

• Shielded

SpecificationsCable Type Twisted pair, gray
PVC jacketCapacitance 30 pF/ft.Conductor
Gauge 22 AWG (7 x 24 AWG), strandedResistance
16 ohms/1000 ft. (max.)Shield Foil around
each pair, each with a drain wire 
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Cables-Twisted Pair
Unshielded UTP
UL listed/CSA approved. ETL verified to TIA 568
TSB 40A specifications. Constructed of solid or
stranded wire. All are 24 AWG, except the
EVMSL06A which is 26 AWG. Low attenuation and
near-end cross talk (NEXT) for 100-MHz
applications. Capacitance is 14 pF/ft
Impedance is 100 15 ohms. 
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UTP Categories

• Established Standards of the EIA/TIA
• EIA/TIA 568A EIA/TIA 568B

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Fiber Optic
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Fiber Optic Cable

• Fiber optic cabling consists of a center glass
  core surrounded by several layers of protective
  materials. It transmits light rather than
  electronic signals eliminating the problem of
  electrical interference. This makes it ideal for
  certain environments that contain a large amount
  of electrical interference. It has also made it
  the standard for connecting networks between
  buildings, due to its immunity to the effects of
  moisture and lighting.

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Network Interface Card

• The NIC serves as the connection between the
  personal computer and the network media.
• It connects to the computer on its base by
  plugging into an expansion slot of the computer.
• Another connection is accessible from the outside
  of the computer and has connections for the
  cables to plug into the network.

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Fiber optic cable

• Can transmit signals over much longer distances
  than coaxial and twisted pair. Carrys information
  at vastly greater speeds. This capacity broadens
  communication possibilities to include services
  such as video conferencing and interactive
  services. Fiber optic cabling cost is comparable
  to copper cabling it is more difficult to
  install and modify. 10BaseF refers to the
  specifications for fiber optic cable carrying
  Ethernet signals.

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Fiber Optic Cable

• Facts about fiber optic cables Outer insulating
  jacket is made of Teflon or PVC. Kevlar fiber
  helps to strengthen the cable and prevent
  breakage. A plastic coating is used to cushion
  the fiber center. Center (core) is made of glass
  or plastic fibers.

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Fiber Optic Connector

• The most common connector used with fiber optic
  cable is an ST connector. It is barrel shaped,
  similar to a BNC connector. A newer connector,
  the SC, is becoming more popular. It has a
  squared face and is easier to connect in a
  confined space.

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Fiber Optic cable

• The features of fiber-optic cable systems are
• Expensive
• used for backbones or FDDI rings (100MB/s)
• long distance
• high capacity
• immune to electro magnetic interference
• low loss
• difficult to join
• connectors are expensive

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Fiber Optic cable

• Fiber optic is often used to overcome distance
  limitations. It can be used to join two hubs
  together, which normally could not be connected
  due to distance limitations. In this instance, a
  UTP to Fiber converter is necessary.

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Coaxial cable
Unshielded twisted pair
BNC connector
RJ-45 connector
Fiber optic cable
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Protocol Summary Protocol Cable Speed Topology
Ethernet Twisted Pair, 10 Mbps Linear Bus,
Star, Tree Coaxial, Fiber Fast
Ethernet Twisted Pair, 100 Mbps Star Fiber
Local Talk Twisted Pair .23 Mbps Linear Bus or
Star Token Ring Twisted Pair 4 - 16
Mbps Star-Wired Ring FDDI Fiber 100 Mbps Dual
ring ATM Twisted Pair 155-2488 Mbps Linear
Bus, Star, Tree Fiber
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Specification Cable Type Maximum length

• 10BaseT Unshielded Twisted Pair 100 meters
• 10Base2 Thin Coaxial 185 meters
• 10Base5 Thick Coaxial 500 meters
• 10BaseF Fiber Optic 2000 meters
• 100BaseT Unshielded Twisted Pair 100 meters
• 100BaseTX Unshielded Twisted Pair 220 meters

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Wireless LANs

• Not all networks are connected with cabling some
  networks are wireless. Wireless LANs use high
  frequency radio signals, infrared light beams, or
  lasers to communicate between the workstations
  and the file server or hubs. Each workstation and
  file server on a wireless network has some sort
  of transceiver/antenna to send and receive the
  data. Information is relayed between transceivers
  as if they were physically connected.

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Wireless LANs

• For longer distance, wireless communications can
  also take place through cellular telephone
  technology, microwave transmission, or by
  satellite.Wireless networks are great for
  allowing laptop computers or remote computers to
  connect to the LAN. Wireless networks are also
  beneficial in older buildings where it may be
  difficult or impossible to install cables.

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Wireless LANs

• Two common types of infrared communications used
  in schools are line-of-sight and scattered
  broadcast. Line-of-sight communication means that
  there must be an unblocked direct line between
  the workstation and the transceiver. If a person
  walks within the line-of-sight while there is a
  transmission, the information would need to be
  sent again. This kind of obstruction can slow
  down the wireless network.

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Wireless LANs

• Scattered infrared communication is a broadcast
  of infrared transmissions sent out in multiple
  directions that bounces off walls and ceilings
  until it eventually hits the receiver.

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Wireless LANs

• Networking communications with laser are
  virtually the same as line-of-sight infrared
  networks.Wireless LANs have several
  disadvantages
• very expensive, provide poor security, are
  susceptible to interference from lights and
  electronic devices, and are also slower than LANs
  using cabling.

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Installing Cable - Some Guidelines

• When running cable, follow a few simple rules
• Always use more cable than you need. Leave plenty
  of slack.
• Test every part of a network as you install it.
  Even if it is brand new, it may have problems
  that will be difficult to isolate later.
• Stay at least 3 feet away from fluorescent light
  boxes and other sources of electrical
  interference.

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Installing Cable - Some Guidelines

• If it is necessary to run cable across the floor,
  cover the cable with cable protectors.
• Label both ends of each cable.
• Use cable ties (not tape) to keep cables in the
  same location together.

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Building wiring systems

• Horizontal Wiring The horizontal wiring extends
  from the wall outlet to the system center
  (telecommunications closet). It includes the
• the wall outlet
• the horizontal cable
• cross-connects or patch cables in the
  telecommunications closet (TC)

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Building wiring systems

• Some general features of the horizontal wiring
• uses star topology
• limit of 90 meters (295') from TC to wall outlet
• limit of 3 meters (10') to connect from wall
  outlet to PC
• patch cords and cross-connect leads are limited
  to 6 meters (20')
• minimum of two outlets per user (phonedata)
• standardized media

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Patch Cables

• Two varieties, straight through or reversed. One
  application of patch cables is for patching
  between modular patch panels in system centers.
  These are the straight through variety. Another
  application is to connect workstation equipment
  to the wall jack, and these could be either
  straight through or reversed depending upon the
  manufacturer.Reversed cables are normally used
  for voice systems.

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Patch Cables

• How to determine the type of patch cable Align
  the ends of the cable side by side so that the
  contacts are facing you, then compare the colors
  from left to right. If the colors are in the
  same order on both plugs, the cable is straight
  through. If the colors appear in the reverse
  order, the cable is reversed.

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Backbone Wiring

• The backbone wiring system interconnects
  telecommunication closets, equipment rooms and
  entrance facilities (ie, the outside world). Some
  general features are
• star topology
• maximum of two hierarchical levels
• interconnections between any two TC must not go
  through more than 3 cross connects
• use of recognized media
• adherence to distance limitations

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NETWORK SEGMENTS

• A network segment is a length of cable
• devices can be attached to the cable
• it has its own unique address
• it has a limit on its length and the number of
  devices which can be attached to it

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Ethernet Cards

• usually purchased separately from a computer
• pre-installed Ethernet card (Dell Optiplex)
• contain connections for either coaxial or twisted
  pair cables (or both)
• designed for coaxial cable, the connection will
  be BNC
• twisted pair design has a RJ-45 connection
• Some cards also contain an AUI connector
• used to attach coaxial, twisted pair, or fiber
  optics cable

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Network Interface Card

• The NIC serves as the connection between the
  personal computer and the network media.
• It connects to the computer on its base by
  plugging into an expansion slot of the computer.
• Another connection is accessible from the outside
  of the computer and has connections for the
  cables to plug into the network.

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NIC
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Network Interface Card
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SPECIFICATIONS3Com Fast Ether Link Server
Network Interface CardCable Requirements
Category 5 2pair UTPHardware PCI 2.1
compatible serversMaximum Distance 100 m
(328.1 ft.)Management SNMPOperating Systems
NetWare 4.x, 5.0, Windows NT 4.0, SCO
UnixWare 7Standards IEEE 802.3 10BASET,
IEEE 802.3u 100BASETX , IEEE 802.1QIndicators
LEDs Link Status, Speed, ActivityConnectors
(1) RJ45
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Network Cards

• ISA Cards
• PCI Cards
• Contain the MAC address
• 0058799033A3C203
• First 24 bits identify the company
• Last 24 bits are assigned by the company