IT Essentials II Network Operating Systems

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IT Essentials IINetwork Operating Systems

• Chapter 3Physical Components of a Networks

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Network Interface Card

• Considerations on selecting a NIC
• Type of network
• Type of media
• Type of system bus
• The options for assigning IP addresses for hosts
  on a LAN are
• Static Assigned by the network administrator
  manually
• Dynamic Assigned by a Dynamic Host
  Configuration Protocol (DHCP) server (DHCP
  servers are discussed in the next section.)
• Automatic Private IP Addressing

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Default Gateway
The default gateway is the "near-side" interface
of the router, that is, the interface on the
router to which the local computer's network
segment or wire is attached
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Topologies

• Network Topologies
• Bus Topology
• Star Topology
• Ring Topology
• Mesh Topology
• Hybrid Topology
• Combines more than one of above
• Physical topology
• Layout of devices and media
• Logical Topology
• Path the signal takes from A to B

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Bus Topology

• Advantages
• cabling is quite inexpensive.
• It uses less cable
• Good for less than 10 devices
• It doesn't need a central device
• Disadvantages
• slower access to the network
• less bandwidth due to the sharing of the same
  cable by all devices.
• Hard to identify and isolate problems.
• A break at any point in the bus cable can disable
  the entire bus network.
• It needs terminators.

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Star Topology

• Most common
• Advantages
• It is easily upgradeable
• The star topology is flexible
• The star topology is reliable
• It is easy to design and install
• Easy diagnosis of problems
• allows for more throughput than any other
  topology.
• Disadvantages
• It requires a lot of cable to connect
• It is more expensive to build

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Ring Topology

• Advantages
• It is easier to locate problems
• Separate terminators are not needed
• Collisions cannot occur
• Disadvantages
• A break at any point in most types of ring
  networks will disable the network.
• The addition of a new computer to the network
  will require an interruption in the network.
• equipment for ring networks is not readily
  available.
• There is limited bandwidth and access.

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Mesh Topology

• All devices (nodes) connect to each other for
  redundancy and fault tolerance
• Used in Wide Area Networks (WANs) to interconnect
  LANs and for critical networks like those used by
  governments
• Is expensive and difficult to implement

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Media Types

• Copper
• Coaxial cable
• Twisted-pair cable
• Glass
• Fibre-optic cable
• For each type of Cable there are two types
• Plenum
• Fire retardant for use in space between ceiling
  and floors
• PVC (Polyvinyl Chloride)
• Gives off a poisonous gas when burned
• Waves
• Wireless

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Coaxial Cable

• Advantages of coaxial
• It can be run for longer distances between nodes
  than twisted-pair cable. 
• It is less expensive than fibre-optic cable.
• Disadvantages of coaxial
• Thicknet's large diameter makes installation
  difficult.
• Coax needs to be grounded, otherwise noise
  problems will cause data errors.
• Bandwidth is limited.

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Twisted-Pair Cable

• Two basic types
• Shielded Twisted-Pair (STP)
• Unshielded Twisted-Pair (UTP)
• Category 3 is the wiring used for telephone
  connections
• Category 5 and 5e are currently the most common
  Ethernet cables used
• Category 6 is the newest category and has not yet
  been ratified by cabling industry organizations

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Fibre-optic Cable

• Advantages
• Not susceptible to electromagnetic or radio
  frequency interference
• Longer distances can be spanned
• No need to ground cable when used between
  buildings
• Capable of higher data rates than copper media
• Disadvantages
• Expensive labour and material costs

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Wireless

• There are two approaches currently being used to
  implement spread spectrum for WLAN transmissions,
  namely
• Frequency Hopping Spread Spectrum (FHSS)
• Direct Sequence Spread Spectrum (DSSS)

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Devices

• Hub and Repeaters
• A repeater receives the signal, regenerates it,
  and passes it on
• Hubs are actually multi-port repeaters
• Bridges and Switches
• make intelligent decisions about whether or not
  to pass signals on to the next segment of a
  network
• Routers
• make smart decisions on how to send data from one
  segment to another

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Connecting to Internet

• Synchronous serial lines
• sent together with a synchronizing clock pulse
• NICs
• Digital modems
• Asynchronous serial lines
• sent without a synchronizing clock pulse,
  receiving device synchronizes its clock with
  sender
• Analogue modems
• PC serial ports
• Modems
• Dial-up networking
• ISP and Internet backbone providers
• DSL
• Cable modems

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Modem

• There are four main types of modems
• Expansion cards
• PCMCIA modems
• External modems
• Built-in modems

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Modem AT Commands
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ISP and Internet Backbone Providers

• Services of an Internet Service Provider (ISP)
  are usually needed in order to surf the Internet

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Digital Subscriber Line (DSL)

• Advantages
• Offers high speeds at a fraction of cost
• Service can be added incrementally as more users
  subscribe
• Both voice and data can be transmitted at the
  same time
• Always on technology
• Backward compatible with analogue phones
• Disadvantages
• Availability is limited
• Best voice support still not decided
• The Telco Central Office must have DSL equipment
  installed

• Types
• ADSL
• Asymmetric DSL
• SDSL
• Symmetric DSL
• IDSL
• ISDN DSL
• HDSL
• High Data Rate DSL
• VDSL
• Very High Data Rate DSL

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Cable Modem

• Advantages
• Existing cable TV offers high availability
• Cable TV infrastructure upgraded with HFC has
  addressed service bottlenecks
• Disadvantages
• Almost always requires an overhaul of cables
• Being a shared media, more users equal less
  bandwidth

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Questions?