Internet and LAN Technology

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Internet and LAN Technology

• Chapter 5

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Why install networks?

• Share resources such as printers or storage space
• Reduce costs
• Enable people to share documents easily
• Allow people to work together regardless of
  geography or time

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Disadvantages to Networks

• Susceptible to attacks and unauthorized access
• Widespread network problems can cause loss of
  productivity
• Access to additional resources (Internet) can
  also lead to decrease in worker productivity

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Different ways to classify networks

• Geographical scope-how much area does it serve?
• Organizational structure-what is the hierarchy of
  devices attached?
• Physical typology-how is it arranged or what is
  the shape of the network?
• Network lines-what cables or substitute is
  responsible for moving data around the network?
• Bandwidth-how much data can it carry?
• Protocols used-does it use TCP/IP or something
  else?

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Geographical

• PAN-personal area network (a computer and devices
  within 30 feet usuallly a computer and a wireless
  device such as a printer)
• LAN-large area network (a small business or part
  of a larger network, i.e. the library LAN or a
  home network)
• MAN-metropolitan area network covers a city or
  metropolitan area such as ISPs or cable modem
  networks
• WAN-wide are networks that share information
  across great distances such as nationwide bank
  networks

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Organizational

• Client/server where one server provides services
  to one or many clients
• Peer to peer networks where all computers are
  equal and there isnt a server doing all of the
  workeveryone shares jobs.

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Members of the Network

• The items in a network can consist of
• a server
• client or workstation
• networked peripheral such as a printer
• network devices which help broadcast and boost
  signals on network

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Network Hardware

• In addition to the computers and shared
  peripherals on the internet, there are

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Physical Topologies - Star

• Server is centrally located
• All traffic must travel through central computer
• Can be problematic if central computer breaks
  down
• Central point can be a HUB with a repeater which
  broadcasts and boosts the signal across the
  network

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Ring Topology

• Connects all devices in a circle
• Uses less cable than star topology
• Can be dangerous if one computer fails
• Infrequently used

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Bus Topology

• Uses common backbone to connect devices
• Connected together like a daisy chain
• Works best with few dozen computers
• Trouble if backbone fails

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Mesh Topology

• Connects each device to many others
• Data can take many different paths in case one
  goes down
• Original plans for internet were based on mesh
  topology

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Tree Topology

• Combines star and bus networks
• Attaches star configurations to a bus backbone
• Many schools and businesses use this plan

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Networking Hardware

• In addition to Hubs and repeaters, many networks
  need hardware to connect different networks
  together
• Bridges connect similar networks
• Gateways and routers join networks that are
  different

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More Networking Hardware

• Devices either need to be linked together with
  wires or through wireless technology
• Wires come in three flavors
• Twisted pairs-refers to the twisted pairs of
  copper wires usually used in LANs such as
  computer labs and dorms
• Coaxial cable has a copper wire encase in
  insulation usually used with cable modemscable
  TV too!
• Fiber optic cable has strands of glass that
  conduct data using miniature lasers used for
  higher traffic areas such as backbones and some
  larger business and campus networks

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Wireless Networks

• Generally operate of RF signals (radio frequency)
  or microwaves
• Hardware needed includes a transceiver which
  operates as both a transmitter and receiver
• Radio and microwaves cant bend around earth so
  satellites are needed
• Satellite has a transponder which receives the
  signal, amplifies it, and retransmits
• Infrared can also transfer data for short
  distances with a clear line of sight

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What is bandwidth?

• Bandwidth is the transmission capacity of a
  communications usually measured in bits per
  second
• Higher bandwidth options such as DSL and cable
  access are considered broadband connections
• Lower bandwidth connections are considered
  narrowband

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How does data travel on a network?

• Protocols handle the various tasks such as
  dividing the information into packets and
  shipping the to the right location
• Protocols can regulate traffic in a number of
  ways
• Simplex is data travelling in one direction only
  (radio or TV)
• Half duplex allows traffic in both directions but
  only one at a time (walkie talkies)
• Full duplex allows traffic in both directions at
  the same time (telephone conversation)

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More on Local Area Networks (LAN)

• Controlled by standards so everyones LAN works
  in the same way
• Can use ARCnet, Token Ring or FDDI (Fiber
  distributed data interconnect)
• Many use Ethernet because it is fast and
  inexpensive

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More on Ethernet

• Ethernet technology simultaneously broadcasts
  data to all devices on the network and is only
  accepted by the device it is addressed to
• Ethernet is generally cabled with twisted pair or
  fiber optic cables
• Generally requires an ethernet card which acts as
  the computer network interface card

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Wireless Technology

• Wi-Fi (wireless fidelity) refers to networking
  standards for the most popular wireless network
  technology
• Wi-Fi hotspots are wireless access points in
  stores and restaurants such as Starbucks and
  Borders
• Wi-fi requires an access point which acts as a
  hub.
• A wi-fi card is required to connect your computer
  to the wireless network
• Some wi-fi hotspots are free, others require
  service with companies such as T-Mobile
• Bluetooth is a wi-fi alternative but generally
  only carries signals for short distances.

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Problems with Wireless Networks

• Slower transmission speeds than Ethernet
• Susceptible to interference from similar devices
  such as cordless phones
• Security
• War driving or LAN jacking where people use
  wireless signals to access networks and possibly
  data on that network
• Easy to intercept so data must be transmitted in
  an encrypted format (WEP)

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HomePNA and HomePLC networks

• HomePNA uses existing telephone cables and a
  special network interface card (NIC) to transfer
  data in a home network
• HomePLC uses a special NIC card and the
  electrical outlets in your home to transfer data

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The Internet--History

• When the Russians launched Sputnik the US felt
  they were falling behind and created a network
  called ARPANet to connect scientists to allow
  them to share info
• In the early 1990s new programs were developed to
  make the internet easier to use
• Today, over 500 million users use the internet
  transferring over 100 trillion bytes per week

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Internet Structure

• The internet is not owned by anyone
• Network Service Providers (NSP) such as ATT and
  Sprint maintain the backbones and routers of the
  Internet
• Network Access Points (NAP) connect backbones
  from different providers
• Large ISPs connect directly to the backbones and
  smaller ISPs generally connect to a larger ISP

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Internet Protocols

• TCP/IP is used for dividing the info into packets
  and then sending it on its way
• HTTP is used to exchange info via web pages
• FTP transfers files between computers
• SMTP, POP, and IMAP are all email protocols

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IP Addresses

• In order for info to travel the net it need to
  know where to go and uses IP addresses.
• IP numbers looks something like this
  123.34.46.255
• When you logon to surf the internet, your ISP
  assigns your computer a dynamic IP address that
  will be different next time you log on
• Sometimes you need to assign one IP address to a
  machine for a long time so you give it a static
  IP address

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Domain Names

• Instead of remembering those IP addresses, we
  substitute names such as tarleton.edu because
  theyre easy to remember and type
• These name substitutions for IP addresses are
  called domain names
• The last part of the domain name such as .com or
  .edu designates the top-level domain and
  indicates what type of site it may be

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Some Top Level Domains

• .com commerce site
• .edu education site
• .net generally used for ISP but has expanded
• .gov for US government
• .mil for US military
• .org for non-profit organizations
• .au, .jp,.uk generally are geographical
  designations for countries such as Australia,
  Japan and the United Kingdon

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More on Domain Names

• Domain servers sit out on the internet and lookup
  the corresponding IP address for the domain name
  youve entered and sends you on your way
• You may want to purchase your own domain name if
  you are going to operate a business or large
  website
• You must choose a domain name that is not already
  being used and pay a fee

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Voice Over IP

• VoIP allows you to speak into your computers
  microphone and have it delivered via the internet
  to another computer, allowing for conversations
• Many times can be used to eliminate long distance
  fees but the quality is not always the best

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How does dial-up actually work?

• Your modem places a regular telephone call using
  POTS (plain old telephone system) to transfer
  data.
• Your ISP answers your modems phone call and a
  router sends it out to the Internet
• Your modem (which comes from modulation and
  demodulation) is responsible for changing audio
  signals into digital signals and then back again
• Modems can be measured in baud rate but more
  commonly now are measured in capacity such as
  kbps
• Even though much of the phone system in this
  country is digital, you still need a modem
  because the local cable from your house to the
  telephone company is still designed to carry
  analog signals

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What is accelerated dial-up?

• Data is not actually sent faster than normal
  dial-up, just uses some tricks
• Server compresses data even more at the ISP
  before it is delivered to the client
• Server also caches or temporarily stores copies
  of popular pages so the download only goes from
  the ISP to the customer and not out on the web
• Does not improve file download time such as music
  and video files which are already compressed
• Generally costs anywhere from 11-20/month

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Cable modem connections

• The cable from the cable company has the
  potential to deliver TV signals, accept data, and
  send data all on the same wire
• Cable internet subscribers are all connected to a
  neighborhood network with the cable company
  routing your data onto the internet
• You need a special cable modem that translates
  the cable data into data that your computer
  understands that is generally then connected to
  your computer via ethernet cable
• Note that the more customers that join the
  network, the potential for slower connections
  grow as everyone share the same bandwidth

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More on DSL

• DSL is an always-on high speed connection that
  uses standard phone lines
• Can simultaneously carry voice and digital data
• Speed varies and signal degrades over distance
• Requires a DSL modem