Computer Networking – Part 2
CS 1 Worksheet
Networking – Part 2
•Circuit Switching versus Packet Switching
•Wireless
•Careers in Information Technology
WAN Link Options
•Circuit Switching: A form of data communication which
_________________________________________________________________________ to carry the data
stream.
•Like a conventional telephone system.
•When a subscriber makes a telephone call the dialed number is used to set switches in the
exchanges along the route of the call so that there is a continuous circuit from the originating caller to
that of the called party.
•Packet Switching: A form of data communications which
___________________________________________________________________________ by the best
available channels and reassembles the original data stream at its destination.
•An alternative is to allocate the capacity to the traffic only when it is needed, and share the available
capacity between many users.
Wireless Access Point
•A wireless access point is a device that connects __________________________ (laptops, etc.)
__________________________, usually an Ethernet LAN.
Wireless Access Point
•In our example the wireless access point (AP) will __________________________.
Putting it together
•Exactly the same as connecting a router without an AP.
Configuring the AP and Router
Wireless Settings:
•__________________________ (Service Set Identifier) – Name of your network
•__________________________: WPA, WEP, or none
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SSID
•The SSID is what will be displayed when people with wireless computers are looking for a wireless
LAN.
Router Information
•IP Address from ISP
•Connects to your DSL/Cable Modem
•NAT (Network Address Translation)
Local Network
•Switch or Hub
•Connect “wired” computers
•DHCP Server (optional)
Wireless
•SSID: MyHomeNetwork
•DHCP Server: (optional)
•Channel: 11
•Encryption Function: WPA
You choose…
•There are many resources to discuss the possible health risks or wireless LANs.
•As a networking and WLAN user and instructor I have my own thoughts which I will share.
•If you are concerned, then research the information and come to your own conclusions.
•The following information is from my own research and experience.
Wireless Frequency
•Wireless APs operate at:
–__________________________
–__________________________
•2 GHZ!
That’s the same as my microwave oven, isn’t that dangerous?
•Answer: No.
–Electromagnetic waves happen naturally.
•Light is an electromagnetic wave
–It is not the frequency, but the wattage, the power.
•Any electromagnetic wave can be dangerous with too much power.
•A 25 watt light bulb is safe, but it wouldn’t be safe at 250,000 watts
–Wireless access points generate signals at 1/10th of a watt.
•Like all electromagnetic waves, the signal does not fade in a linear manner, but inversely as the
square of the distance.
Inverse square law
•Double the distance of the wireless link, we receive only ¼ of the original power.
•Triple the distance of the wireless link, we receive only 1/9 the original power.
•Move 5 times the distance, signal decreases by 1/25.
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Putting it in some perspective
•Measurements from an antenna transmitting 100mW at 1 inch
•Remember a milliwatt is 1/1,000th of a Watt
•Microwave oven typically operates at 1,000 watts in a confined space.
1”
100 mW
1/10th watt
2”
25 mW
1/40th watt
4”
6.25 mW
1/166th watt
8”
1.56 mW
1/1000th watt
16”
0.39 mW
4/10,000th watt
32”
0.097 mW
1/10,000th watt
64” (5.3 ft)
0.024 mW
2/100,000th watt
128” (10.6 ft)
0.006 mW
6/1,000,000th watt
256” (21.3 ft)
0.0015 mW
15/10,000,000th watt
•Light bulbs would also be dangerous the were 10,000 to 1,000,000,000,000 stronger.
•A 250,000 watt up to a 250,000,000,000,000 watt light bulb would also be dangerous.
Wireless Security – Everyone can hear
•Others can “hear” or capture your information.
•Wireless signals are propagated, sent, similar to our __________________________.
Wireless Security – Everyone can hear
•If we don’t want them to understand what they hear, we can encrypt or code the information.
•As long a our wireless computer and access point are using the same encryption algorithm, such as
____________________________________________________.
Wireless Security - WPA
•WPA (WiFi Protected Access) is currently the __________________________.
•The password is configured on both the wireless access point and the computer.
Wireless Security
•Without any security, anyone can:
–____________________________________________________ to access your network and the
Internet.
–____________________________________________________ from your wireless computer.
Wireless Security
•Your web browsing or email access should already be secured.
•____________________________________________________
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