Hands-on Networking Fundamentals

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Hands-on Networking Fundamentals

• Chapter 4
• Connecting Through a Cabled Network

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Communications Media Types

• OSI Layer 1 communication media and interfaces
• Five basic communication media types
• Coaxial cable based on copper wire
• Twisted-pair cable based on copper wire
• Fiber-optic cable glass or plastic cable
• Hybrid fiber/coax combines copper and fiber
• Wireless technologies radio or microwaves
• Suitability of media varies with different
  networks
• Example uses of coaxial cable
• Older LANs
• LANs in areas with signal interference strong
• Connecting wireless antenna to network device

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Communications Media Types (continued)

• Consider capabilities and limitations of media
• Factors affecting choice of LAN or WAN medium
• Data transfer speed
• Use in specific network topologies
• Distance requirements
• Cable and cable component costs
• Additional network equipment that might be
  required
• Flexibility and ease of installation
• Immunity to interference from outside sources
• Upgrade options
• Security

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Coaxial Cable

• Two types of coaxial cable (coax)
• Thick used in early networks, typically as
  backbone
• Backbone cabling between network equipment
  rooms, floors, and buildings
• Thin used to connect desktops to LANs
• Has much smaller diameter than thick coax
• Use of both thick and thin coaxial cables
  declining

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Twisted Pair Cable

• Twisted-pair cable
• Contains pairs of insulated copper wires
• Outer insulating jacket covers wires
• Communication specific properties
• Copper wires twisted to reduce EMI and RFI
• Length up to 100 meters
• Transmission speed up to 10 Gbps
• RJ-45 plug-in connector attaches cable to device
• Less expensive and more flexible than
  T-connectors
• Two kinds of twisted pair cable shielded and
  unshielded (preferred)

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Activity 4-4 Building a UTP Cable

• Time Required Approximately 2030 minutes
• Objective Experience building a UTP cable.
• Description In this activity, you attach 4-pair
  UTP cable to an RJ-45 connector. You need the
  cable, a crimper, a connector, and a wire
  stripper. These instructions and Figure 4-6
  follow the EIA/TIA-568-B standard.

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Fiber-Optic Cable

• Fiber-optic cable
• One or more glass or plastic fiber cores encased
  in glass tube (cladding)
• Fiber cores and cladding are surrounded by PVC
  cover
• Signal transmissions consist light (usually
  infrared)
• Three commonly used fiber-optic cable sizes
• 50/125 micron
• Micron (µm) millionth of a meter
• 50 represents core diameter
• 125 represents cladding diameter
• 62.5/125 micron
• 100/140 micron

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Gigabit Ethernet

• Gigabit Ethernet (1000BaseX)
• Provides data transfer of up to 1 Gbps
• Uses CSMA/CD access methods
• Upgrade path for 100BaseX Ethernet networks
• Uses of Gigabit Ethernet
• Alternative for backbone LAN congestion
• Attract token ring users with star-based
  topologies
• Gigabit Ethernet target
• Installations using Layer 3 routed communications
• Separate standards for fiber-optic and
  twisted-pair cables

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The Role of Firmware and NIC Drivers

• Firmware and NIC driver support communications
• Firmware software stored on a chip, such as ROM
• NIC Driver manages how packets or frames sent
• Firmware or driver may automatically detect media
  
• Some NIC drivers can be signed
• Driver signing placing digital signature in
  driver
• Functions of digital signature
• Ensures driver compatible with operating system
• Certifies that driver tested for defects or
  viruses
• Ensures that driver cannot overwrite new driver

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Half- and Full-Duplex NIC Communications

• Two transmission modes for NIC and network
  equipment
• Half-duplex send and receive, not at the same
  time
• Full-duplex parallel sending and receiving
• Made possible by buffering at NIC
• Buffering temporarily storing information
• Full-duplex is a good choice
• Usually faster than half-duplex

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Hands-on Networking Fundamentals

• Chapter 5
• Devices for Connecting Networks

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LAN Transmission Devices

• Uses of LAN transmission equipment
• Connecting devices on a single network
• Creating and linking multiple networks or
  subnetworks
• Setting up some enterprise networks
• Connecting devices that will be discussed
• Repeaters, MAUs, hubs, bridges, routers,
  brouters, switches, gateways

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Repeater

• Connects two or more cable segments
• Retransmits incoming signal to all other segments
• Cable segment is run within IEEE specifications
• Example Ethernet segment in star-bus network
• Performs four Physical layer functions
• Filter out signal disturbance caused by EMI and
  RFI
• Amplify and reshape incoming signal
• Retime the signal (in Ethernet applications)
• Reproduce the signal on all cable runs

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Multistation Access Unit

• Multistation access unit (MAU or MSAU)
• Central hub on a token ring network
• May have intelligence built-in to detect problems
• Smart multistation access unit (SMAU)
• Tasks performed by MAU
• Connect nodes in a logical ring upon a physical
  star
• Move the token and frames around the ring
• Amplify data signals
• Expand token ring network by daisy-chain
  connections
• Provide for orderly movement of data
• Shut down ports to malfunctioning nodes

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Hub

• Central network device connecting nodes in star
• Functions of a hub
• Centrally connect multiple nodes into one network
• Permit connections on single or multiple LANs
• Provide multi-protocol services
• Consolidate the network backbone
• Provide connections for several different media
  types
• Enable centralized network management and design
• Unmanaged hub (simplest)
• Logical bus or token ring physically connected as
  star
• May be active or passive

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Bridge

• Network device connecting LAN segments
• Functions of a bridge
• Extend LAN when maximum connection limit reached
• Example the 30-node limit on an Ethernet bus
• Extend a LAN beyond the length limit
• Example beyond 185 meters for thinnet segment
• Segment LANs to reduce data traffic bottlenecks
• Prevent unauthorized access to a LAN
• Operates in promiscuous mode
• Examine frame's physical destination address
• Occurs at MAC sublayer of OSI Data Link layer

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Bridge (continued)

• Translational bridge
• Converts frame to new access method and media
  type
• Example from token ring to Ethernet
• Discards addressing information not used in
  Ethernet
• Three primary bridge functions
• Learning learn network topology and device
  addresses
• Information stored in a bridging table
• Filtering do not flood certain frames, discard
  others
• Enables bridge to used for security purposes
• Forwarding transmit frames to destination
• Based on data built-in to bridging table
• Some bridges are used to cascade network segments

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Spanning Tree Algorithm

• Defined by the IEEE 802.1d standard
• Bridges frames in networks with more than two
  bridges
• Sets up a system of checks performed by bridges
• Two motivations for using spanning tree algorithm
• Ensure a frame does not enter infinite loop
• Causes congestion that may intensify to broadcast
  storm
• Forward frames along the most efficient route
• Efficiency based on distance and utilization of
  resources
• Services for frames performed by algorithm
• Create one-way path around network (use bridge
  data)
• Establish maximum number of hops for maximum
  route
• Enable bridges to send frames along best route

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Router

• Learns, filters, and forwards like a bridge
• Differs from a bridge in significant ways
• Connect LANs at the Network layer of the OSI
  model
• Add intelligence to bridge capabilities
• Receive regular communications from nodes
• General functions of a router
• Reduce traffic by efficiently directing packets
• Join neighboring or distant networks
• Connect dissimilar networks
• Prevent bottlenecks by isolating portions of a
  network
• Secure portions of a network by acting as a
  firewall

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Router (continued)

• Uses a metric to determine optimal routes
• Components which may inform metric calculation
• Number of incoming packets waiting at a
  particular router port
• Number of hops between sending and receiving
  segments
• Number of packets that can be handled in time
  frame
• Size of the packet (large packet may be
  subdivided)
• Bandwidth (speed) between two communicating nodes
• Whether a particular network segment is available
  
• May isolate segments to avert congestion

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Static and Dynamic Routing

• Static routing requires routing tables
• Routing tables specify paths between routers
• Tables set up and maintained by network
  administrator
• Dynamic routing independent of network
  administrator
• Functions automatically performed in dynamic
  routing
• Determine which other routers can be reached
• Determine shortest paths to other networks with
  metrics
• Determine when path to a router is down or
  unusable
• Use metrics to reconfigure alternative routes
• Rediscover router and network path after
  restoration

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Routing Tables and Protocols

• Routers maintain two important databases
• Routing table contains addresses of other
  routers
• Network status contains information about
  traffic, topology, and status of links
• Databases updated by regular exchange of data
• Router forwards packet on basis of metrics
• Routers use one or more protocols
• Multiprotocol type each protocol has address
  database
• Two common communication protocols RIP and OSPF

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Routing Tables and Protocols (continued)

• Routing Information Protocol (RIP)
• Determines shortest number of hops to other
  routers
• Information added to each router's table
• Disadvantages
• Updates containing entire routing table create
  traffic
• Only uses hop count as a metric
• Open Shortest Path First (OSPF) protocol
• Sends only portion of table related to immediate
  links
• Packages routing information in compact form
• Local routers LAN-based
• Join LANs segment traffic act as firewalls

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Switch

• Dual purpose
• To provide bridging capacity
• To increase bandwidth
• Bridge-like characteristics of switch
• Operates at Data Link MAC sublayer
• Uses table information to filter and forward
  traffic
• LAN uses two switching techniques (fabric)
• Cut-through forward portions of frame
• Store-and-forward frame buffered until link
  available

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Gateway

• Software or hardware interface
• Enables two networked or software systems to link
• Functions of a gateway
• Convert common protocols to specialized type
• Convert message formats from one format to
  another
• Translate different addressing schemes
• Link a host computer to a LAN
• Provide terminal emulation for connections to
  host
• Direct electronic mail to the right network
  destination
• Connect networks with different architectures
• Can function at any OSI layer

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WAN Transmission Devices

• WAN transmission over two network types
• PSTN (public switched telephone networks)
• Leased telephone lines such as T-carrier or ISDN
• Characteristics of WAN transmission equipment
• May have analog component or be completely
  digital
• Converts signal for long distance communications
• Creates multiple channels in medium (grow
  bandwidth)
• Frequently used WAN transmission devices
• Telephone modems, ISDN adapters, cable TV modems,
  DSL modems/routers, access servers, routers

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Telephone Modems

• Modem (modulator/demodulator)
• Converts outgoing binary (computer) signal to
  analog
• Converts incoming analog signal to a binary
  signal
• Two ways to attach a modem to a computer
• Internal installed in computer using expansion
  slot
• External attached to serial port connector via
  cable
• Three common types of connectors
• DB-25 connector, DB-9 connector, USB
• Modem data transfer rate measured in two ways
• Baud rate number of signal events per second
• Bits per second (bps) bits per second

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Telephone Modems (continued)

• Data terminal equipment (DTE)
• Device that prepares data for transmission
• Data transfer speed of PC is DTE communications
  rate
• Data communications equipment (DCE)
• Device (modem) that converts data from DTE
• Speed of modem is DCE communications rate
• Modems use two communication formats
• Synchronous continuous data bursts controlled by
  clock
• Asynchronous discrete signals delimited by start
  and stop bits

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Cable TV Modems

• Uses two channels to communicate
• Upstream transmit outgoing data, sound, TV
  signals
• Downstream receive and blend incoming signals
• Factors affecting transmission speed
• Modem speeds may differ upstream and downstream
• Example 30 Mbps upstream, 15 Mbps downstream
• Maximum bandwidth reduced by other subscribers
• Cable hub handles maximum of 30 Mbps
• Cable service may impose policy limits
• Data Over Cable Service Interface Spec (DOCSIS)
• Also called Certified Cable Modem Project
• Provides standards and certifications

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DSL Modems and Routers

• Digital Subscriber Line (DSL)
• Works over copper wire likes ISDN
• Requires intelligent adapter in connecting
  computer
• Intelligent adapter sends digital signal over
  copper wire
• Simplex communication over copper wire
• Dedicated lines for incoming and outgoing signals
• Transfer 2.3 Mbps upstream, 52 Mbps downstream
• Advantages of DSL over cable
• Dedicated DSL line more secure
• Dedicated DSL provides full bandwidth
• DSL networks utilize combined DSL adapter/router

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Remote Routers

• Operate over long distances
• Connect ATM, ISDN, frame relay, high-speed
  serial, and X.25 networks
• Example connect networks from NY to LA into WAN
• Similarities with local routers
• Can support multiple protocols
• Can be set up as a firewall
• Most routers connect to WAN through serial
  interface
• CSU/DSU for T-carrier communications
• Channel service unit (CSU) interface to
  T-carrier line
• Data service unit (DSU) digital interface to CSU
• Modular adapter for other high-speed connections