Chapter 4 Highlights

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Chapter 4 Highlights Computer Networks
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Why network or connect computers?

• Share Data/Files
• Share Hardware
• e.g. Printers, Scanners
• Access Company
• Information Systems
• Share Internet Connection
• Communicate
• e.g. Telephone (VOIP), Chat, E-mail, Video
  Conference)
• In the home, you can share entertainment devices

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LAN Local Area Network In the 1980s companies
began networking their computers. Various
topologies and LAN protocols were used. The star
topology using Ethernet has become the standard
today.
Star Topology Typical of 10BaseT
Ethernet100BaseT Ethernet Gigabit Ethernet
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Categories of Networks

• Local area network (LAN) covers a relatively
  small geographical area, such as a home, office
  building, or school.
• Most popular LAN protocol is Ethernet
  running in a star configuration.
• Wide area network (WAN) covers a large
  geographical area. A WAN is often used to
  connect two or more LANS.
• Popular WAN protocols are T1 and T3 lines,
  ATM, and frame relay
• Metropolitan area network (MAN) Some cities
  offer public networks for police, fire, or WiFi
  for all residents.
• Personal area network (PAN) A term that is
  sometimes used for an individual's network of
  personal devices such their PC, phone, headset,
  and printer.
• Intranet A private network for a company that
  is set up like the Internet. This term often
  refers to web sites that are only accessible
  internally at a company.
• VPN A private secure network that uses the
  Internet for data communication. Branch offices
  for a large company may set up an VPN over the
  Internet to communicate to the parent office.
  This is cheaper than purchasing expensive private
  data lines. Security and encryption is essential
  since the Internet is a public network.

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Data Transmission

• Analog versus Digital In analog transmission,
  information is in
• the form of waves. In digital transmission,
  information is sent as
• binary 1s and 0s. Television broadcasts are
  currently converting
• from analog to digital (HDTV). Vinyl records
  stored music as analog
• sound waves. CDs store music digitally.
• Bandwidth Is the speed of data
  communication.It is usually measured in
  bits/second.
• Q If your Internet connection is 2 Mbps, how
  long would it take to download a 2 MB file?
• A We need to convert bytes to bits
• 2 Million Bytes 16 Million Bits.
• At 2 Million bits/second, it would take 8
  seconds to xfer 16 Million bits.
• Q If your Internet connection is 256 Kbps, how
  long would it take to download a 1 MB file?

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Circuit-Switched vs. Packet-Switched The
telephone network is a circuit-switched network
you have a dedicated path between you and the
person you are talking to. The Internet is
packet-switched. Everything sent over the
Internet is broken up into small packets of data
and sent on their way.
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Protocols

• A protocol is the set of rules that defines how
  devices communicate in a network.
• For Internet communication, TCP/IP is used.
  This protocol is how you open web sites, send
  e-mail, etc. Other protocols define how data
  travels around a LAN (e.g. Ethernet), WAN, or a
  wireless network (e.g. WiFi).

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Ethernet - LANs
Ethernet is most popular LAN protocol. It is
used to connect computers at businesses as well
as at your home. In the 1980s, Ethernet LANs
used coax cable in a bus configuration, but now
they use twisted pair wire in a star
configuration. Each network adapter has a
hard-codedMAC address. To see this address on
theEthernet adapter on a PC, open acommand
prompt and type ipconfig /allWindows lists this
as the physical address.
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Cell Phone Transmission
1G The original cell phones (1980s) were
analog transmission 2G Cell phones
switched to digital transmission (1990s). This
added data support such as txt messages. 3G We
are now switching to 3G cell phone service which
offers high-speed Internet.
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WiFi (802.11)
WiFi can be used to create an entirely wireless
network, or to add wireless capabilities to an
existing wired Ethernet network. WiFi Hotspots
refer to public places that users can connect
their laptops. For example Starbucks, or at
Eastfield. Limitations A WiFi network is
designed forno more than 300 feet in distance
and no roaming (like cell phones). WiFi
Standards 802.11b original WiFi standard at 11
Mbps 802.11g current WiFi standard at 54
Mbps 802.11n newest WiFi standard at 300 Mbps
Wireless Access Point
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Wireless - BlueTooth
Bluetooth was designed for wirelessly connecting
personal consumer devices and peripherals.
Bluetooth works over short distances, typically
less than 30 feet. Communication speed is less
than 1 Mbps.
Pairs of devices establish a trusted relationship
by the user entering a shared passkey or PIN.
Trusted devices may encrypt the data that they
exchange over the air so that no one can listen
in.
Growing in popularity is using bluetooth equipped
phones to make payments.
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Summary of Wireless Protocols
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Typical Company Network Diagram
To Branch Office
Internet
router
router
firewall
Database Server Corporate Info System
DMZ
hubswitch
E-mail server
Web server
Wireless Access Point