Chapter 5 Personal Computer Data Communications and Networking

Transcription

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This chapter provides a practical introduction to data
communications and networking for personal
computers. It includes a brief introduction to data
communications, a section on connecting USB devices
such as cameras and printers to personal computers,
and sections on setting up and securing a wireless home
network.
A student who successfully completes this chapter
should be able to:






define the data communications terms used
in the chapter.
describe the nature and importance of data
communications standards. And briefly describe
three common standards for serial data
communications – RS-232c, USB and Firewire.
connect USB devices with and without drivers to
a personal computer and move data between the
devices and the computer.
find manuals and driver software for most
common peripheral devices.
set up a wireless home network.
secure a wireless home network.
Figure 5-1: components of a common home
computer network including: a broadband modem
with an outside Internet connection, a wireless
router, a desk top computer, two laptops, a wireless
printer, and a Nintendo Wii.
Section 5.1 – Serial Data Communications
In this section we will explore personal computer communications by looking at the nature of digital data, the
differences between parallel and serial communication, and three common standards for serial data
communications – RS-232c, USB and Firewire.
5.1a – Digital Data
Digital data is stored as a series of bits. A bit is a binary
digit, a one or a zero, represented in a computer using
electrical, magnetic and optical technology. Everything from
word processing documents to sound, pictures, and video is
represented as a series of bits. CD and DVD technology
store data as bits of information. Today, even broadcast and
cable television are transmitted as binary digital data.
A group of bits is called a word. The number of bits that a
particular computer works with at one time is called the
computer’s word length. Most modern computers have a
32-bit word length, which means that the computer’s central
processing unit works with 32-bit groups of words. Some
new computers have a 64-bit word length.
Figure 5-2: binary digital data, such as that
found on a CD or DVD. Binary (base two)
numbers have two digits – 0 and 1 –
compared to our decimal (base ten) system
with ten digits – 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9.
CIS 103 – Applied Computer Technology
Data Communications
page 2
A byte is an 8-bit word. The term was coined to refer to the word length for early computers, which were mostly
8-bit machines. Today the size of a computer’s memory is still measured in bytes, even though 8-bit computers
are no longer commonly used. We talk about 4 gigabytes of memory, not 4 gigawords of memory. This system,
known as byte-addressable memory, keeps the size of a computer’s memory and the memory addresses used by
software independent from the computer’s word length. It also makes it easier to compare the size of computer
memories for systems that have different word lengths.
5.1b – Parallel and Serial Data Communication
Data communication is the movement of bits of information from one place to another, both inside a computer
and between computers and other digital devices, such as printers, cameras, or other computers on a network.
Bits in a word of data can be moved at the same time over several parallel wires, or one at a time over a single
wire. Parallel data communication is the movement of the bits of data in a word at the same time over several
parallel wires. Serial data communication is the movement of bits of data one at a time over a single wire.
Actually, serial communication often uses two wires – one in each direction, but the bits of each word are still
moved one at a time as a series of signals over a single wire.
Figure 5-3: serial and parallel data communication. These diagrams
show the movement of an 8-bit word, a byte.
Parallel communication is faster than serial communication, but the equipment is more expensive. A serial cable
only needs one data wire, but often has one data wires for each direction. An older 8-bit parallel cable only needs
eight wires for data. Newer parallel cables need 32 or 64 data wires, making them much more expensive than
serial cables. Most data communications cables also have a few extra wires for timing and control signals.
Today serial communication is normally used between computers, or between a computer and a device such as a
printer, to save money. Most computer networks use serial data communication.
Parallel data communication is primarily found inside a
computer, using data busses. A bus is a set of wires that
are grouped together. A data bus is a set of wires used for
data communication, connecting the various parts of the
computer, such as the Random Access Memory (RAM)
and the Central Processing Unit (CPU).
The size of a data bus usually matches a computer’s word
length. So, a CPU that has a 32-bit processor usually has a
32-bit data bus, and moves data from place to place 32
bits at time over the bus. The size of the data bus can
affect how fast a computer system processes data – 64-bit
computers are faster than 32-bit computers, for example.
Figure 5-4: an 8-bit word and an 8-bit data
.bus.
Serial data communication is often used to connect peripheral devices to a computer. A peripheral device, or
simply a peripheral, is a device that is not part of a computer, but that attaches to a computer. An external hard
drive is an example of a peripheral device. A camera is an example of a standalone device that can also be
connected to a computer as a peripheral. Each peripheral device uses certain data communications standards to
connect to a computer.
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Standalone devices, such as cell phones and iPods, that can work independently, but which are often connected to
a computer to download data, share content, and so on, are often called mobile computing devices.
5.1c – Serial Data Communication Protocols and Standards
A communications protocol is a set of rules defining a data communications method, including the electronic
signals to be used, how fast the data should be sent, and so on. All data communication needs to follow a
communications protocol to ensure that the receiver of a message can understand the sender.
Data communication standards include the communications protocol, along with equipment specifications, such
as the type of connectors and cables to be used. It is important for computer companies to follow data
communications standards so that equipment from different manufacturers can work with each other.
There are several organizations that define different data communications standards. Generally, they fall into four
categories:

Government agencies are part of the government and have the force of law. The Federal
Communications Commission (FCC) is a federal government agency in the U.S. responsible for
regulating electronic communications.

Government affiliated agencies work with governments, but are not directly controlled by a single
government. The International Telecommunications Union (ITU) is a UN sponsored organization that
works with governments to standardize international data communications.

Professional groups are organizations whose members are qualified professionals in a certain field. The
Institute of Electrical and Electronics Engineers (IEEE) is a professional association whose members
specialize in electronic engineering, computer science, and related fields.

Trade associations are made up of companies who share a common interest. The Electronics Industries
Alliance (EIA), formerly known as the Electronics Industries Association, is an organization of computer
and electronic equipment manufacturers.
We will look briefly at three serial data communications standards commonly used with personal computers –
RS-232c, USB, and Firewire.
5.1d – RS-232c
The RS-232c standard was created by the EIA in 1969 for terminals
connected to old mainframe computers. It became the standard for
connecting devices like printers and telephone modems to the first
personal computers in the 1970’s and 80’s, but today it is not used
much. You are most likely to see it if you are connecting an older
printer to a computer.
The RS232c standard was important because it was one of the first
communications standards that many different manufacturers
adopted, making is easier to connect one brand of equipment to
another. Such compatibility is commonplace today, largely because
of communications standards.
There are two different types of RS-232c connectors – 25-pin and 9pin. Only two of the pins are used for data, one for each direction,
while the others are used for control and timing signals.
Figure 5-5 shows an RS232c cable with 9 pin connectors, and the
wires bundled inside a plastic sheath. Older RS232c cables looked
like a ribbon, with the wires side-by-side.
Figure 5-5: a nine pin RS232C cable,
like the type used to connect older
printers to computers. Some video
cables use the same nine pin
connectors.
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5.1e – USB
the Universal Serial Bus Implementers Forum
(USB-IF) is an organization formed in the 1990’s
by a group of computer companies, including Intel,
Compaq, Microsoft, Digital, IBM, and Northern
Telecom, to develop a faster and less expensive
data communication standard for connecting peripheral and mobile
computing devices to personal computers. The USB (Universal
Serial Bus) standard is now the most widely used data
communication standard for connecting devices to personal
computers. Commonly used flash ROM drives, sometimes called
memory sticks or thumb drives, are USB devices, as are most newer
printers, digital cameras, and cell phones.
Currently there are three different versions of the USB standard. In
1994 the original USB 1.0 appeared, but it was quickly modified as
USB 1.1, with a maximum data transfer rate of 12 million bits per
second (12 Mbps) and a maximum cable length of 3 meters.
Figure 5-6: a computer with a USB
port and a cable with a USB
connector.
USB 2.0, called Hi-Speed USB, appeared in 2001. It has a maximum data transfer rate of 480 Mbps and a
maximum cable length of 5 meters. USB 2.0 devices are backward compatible with USB 1.1 devices, which
means that they use the same connectors and USB 1.1 and USB 2.0 devices will work with each other, but using
the older protocol.
In November of 2008 the USB-IF introduced USB 3.0, known as SuperSpeed USB. It has a maximum data
transfer rate of 5Gbps (Gigabits per second), and is backward compatible with Hi-Speed USB and USB 1.1.
5.1f – Firewire
Firewire is a serial communication standard first
developed by Apple Computers and approved as
IEEE standard 1394 in 1995. Sony’s version of
Firewire is called iLInk and Texas Instruments
calls their version Lynx. The High Definition
Audio-Video Network Alliance (HANA) has chosen Firewire as
the standard for the audio visual industry, so most professional
video equipment, such as high end video cameras, have Firewire
connections. The automobile industry and the military also use
Firewire. The new F22 Raptor and F-35 Lightning II aircraft are
equipped with Firewire data communication connections, as is
the NASA Space Shuttle.
Figure 5-7: 6-pin and 4-pin Firewire
connectors are common.
There are several versions of Firewire, just as there are several versions of USB. IEEE 1394a, also called
Firewire 400, has a maximum data transfer rate of 400 Mbps. IEEE 1394b (Firewire 800) is capable of 800
Mbps over standard cables and up to 3,200 Mbps using fiber optic cables. Firewire 800 can be used with cables
up to 100 meters long. As with most communications standards, new versions of Firewire are being developed.
Firewire is more sophisticated than USB – it is more reliable at higher speeds and the cables can be much longer –
but the equipment is more expensive and it can be a little harder to use, so USB is far more common for
connecting devices to personal computers.
In the next part of this lesson we will focus on connecting USB devices to personal computers. Firewire and
RS232c connections work in a similar manner, except that driver software is more often needed, and the
connectors are different.
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5.1 Section Review
a.
b.
c.
d.
e.
f.
How is digital data stored inside a computer? why are the terms byte and word length both
important in modern computing?
What is the difference between parallel and serial data communications? Where are each used and
why?
What are data communication protocols and standards, and why are they important? Who makes up
such standards?
What is the RS232c standard and why was it important?
What is the USB standard and why is it important? What are the three different versions of USB?
Who is responsible for the USB standard?
What is the Firewire standard and where is it used? How does it compare with USB? Who is
responsible for the Firewire standard?
—— §——
Section 5.2 – Connecting USB Devices to Personal Computers
In this section we will see how to use USB technology to connect peripheral devices to computers. We will look at
specific examples – connecting a camera to a computer without using driver software, and connecting a printer
that does need driver software.
5.2a Using USB Technology
To connect peripheral USB devices to personal computers you
need to establish a physical connection between the computer
and the device, and make sure that any necessary driver
software is in place. A driver is a computer program that
manages a device or a connection between devices. USB
connections are simple and do not need drivers, but sometimes
the device connected to the computer needs a driver so that it
will work properly.
There are six different standard USB connectors, as shown in
Figure 5-8. You need a cable with the correct connector to
connect a USB device to a computer. A type A connector plugs
into a USB host connection slot on a personal computer.
Devices such as flash memory chips and the end of a USB
extension cable have Type A USB connectors. The other five
types of USB connectors – Type B, Mini-A, Mini-B, Micro-AB,
and Micro-B – plug into the peripheral device. You must make
sure that the USB cable you are using has the correct type of
connector for the device you are trying to connect.
Figure 5-8: six standard USB connectors.
5.2b Moving data from a camera over a USB Connection
Data, including pictures, can be moved from one device to another by connecting the two devices to each other
using a USB cable, or by taking a memory chip out of one device and plugging it into another.
We are going to look at connecting a PC to a Kodak EasyShare C813 digital camera, shown in Figure 5-9. We
will do so without using the software that comes with the camera, which is mostly for editing pictures and
managing albums of picture files.
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Figure 5-9: a Kodak EasyShare C813 digital camera with its packaging, which includes the box, manuals, a
CD with software, batteries, a camera carrying strap, and a USB cable.
To move data from a camera to a computer
Step 1 - Make sure you have the correct cable.
The end of the cable that plugs into the computer is a type A
USB host connector, like the one on a USB thumb drive. The
USB port on the camera, shown in Figure 5-10, is a USB micro
A port, so we need a USB cable with a micro A connector.
Step 2 – Make sure the camera is turned off and that the
computer is turned on and ready to use.
Step 3 – Connect the cable. Plug the USB cable into the
camera and then plug the other end of the cable into a USB port
on the computer.
Step 4 – Turn on the camera and make sure it’s set so that you
can view pictures on the camera’s display screen. You need to
be familiar with the camera or read the instruction manual to see
how to do this.
Step 5 – Open the picture folder. A connection dialog box
should appear on the computer screen, just like it does when you
plug in a flash ROM drive. You should select the [open folder]
option. and then navigate to find the folder in the camera’s
memory that has your pictures.
Figure 5-10: a USB micro B port on the
Kodak EasyShare C813. We need a USB
cable with a micro B connector on one
end.
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Step 6 – Copy the data to the desired location. Once you have found your pictures on the camera, then open the
My Pictures folder on the computer and copy the picture files to the PC. You can copy a single picture file or the
entire folder of pictures – just as you can when copying data from a Flash ROM Drive. You could also make a
folder under My Pictures, or anywhere else on your computer to hold these particular pictures.
That’s it. You can now turn off and unplug the camera and work
with your pictures on the computer. If you double-click a picture file,
it will open using the computer’s default picture software. This will
be the Microsoft Photo Viewer, unless you’ve installed other picture
software on your computer and made it the default for viewing
pictures. You can even print pictures from Microsoft Photo Viewer,
but first a printer needs to be properly connected to the computer.
Alternate Method –An alternate way to move pictures from a
camera to a computer is to take the memory chip out of the camera
and plug it into the computer. There are several formats for memory
chips like this, including SD, SDHD, and XD, but they work the
same way. Of course, this method will only work if your computer
has a slot for the type of chip your camera uses. Adapters that plug
into USB slots are available for most types of memory chips.
Figure 5-11: the Kodak EasyShare
C813with an SD memory card, like the
type the camera uses.
The Kodak EasyShare C813uses an SD memory chip, as shown in
Figure 5-11. So, for this camera’s chip, you need a computer with an
SD memory slot or a chip reader with an SD memory slot that plugs
into a USB port.
Microsoft has a similar lesson online at:
http://www.microsoft.com/windowsxp/using/digitalphotography/takeit/transfer.mspx
5.2c Connecting a USB Printer
Connecting a printer is just like connecting a camera, but
you will probably need printer driver software to make the
printer work properly. The printer shown on the right is an
HP C4480 Photosmart printer, which is similar to many
popular all-in-one color printers that can also be used as a
copier, scanner, and fax machine.
The best way to connect and set up a device that needs
driver software, like a printer, is to follow the instructions
in the manual that comes with the device. So, there are
three basic steps to using such a device:
Figure 5-12: an HP C4480 Photosmart printer.

Find the instructions.

Read the instructions.

Follow the instructions.
But what should you do if you are not sure whether or not a particular device needs a driver? The same three
steps apply – the manual will tell you if your device needs a driver. Also, if you try to establish a connection with
a device that requires a driver, but no driver is present, the operating system will tell you that the necessary driver
is missing.
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But what if you can’t find the manual, or the software that came with the device? Figure 5-13 shows part of the
Web page for downloading the instruction manual and software for the HP C4480 Photosmart printer from the HP
website. Manuals and software and for almost all computer peripheral devices can be downloaded free of charge
directly from the manufacturer.
Figure 5-13: part of the Web page found by searching for “C4480 manual” on the Website www.hp.com.
Notice that you can download a setup guide, a basics guide, or a full user guide. You will need Adobe
Acrobat reader to read or print the manuals, which are in the Adobe PDF format. Most printer
manufacturers have similar manuals that you can find, download, and read or print using Adobe Acrobat
reader, which can also be downloaded free of charge.
It is best to search for the manuals and software directly on the manufacturer’s Website rather than on a general
purpose search engine, such as Google, which could lead you to commercial sites that ask for personal
information or try to sell you related products. You might need to use an Internet search engine to find the
manufacturer’s Web site, but once you locate the manufacturer’s Web site, you should search there for what you
need.
As you can see in Figure 5-13, you can download a setup guide, a basics guide, or the entire manual. The setup
guide will show you how to connect the printer to a computer. Most manufacturer’s Web sites and manuals are
very similar.
You can also do a similar search for the software that comes with the printer. In this case, notice that the menu on
the left on the Web page in Figure 5-13 includes a link for software and driver downloads, which is underlined in
the picture. Figure 5-14 shows part of the Webpage from which you can download the software.
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Figure 5-14: part of the Web page for downloading the software for the HP C4480
Photosmart printer. You can download the basic driver software, download the full software
that comes with the printer, or order a CD with the software. Most manufacturers let you
download the software freely, but charge for sending you a CD.
From this page you can:



download the basic driver software, which is 38.68 Mb long.
download the full feature software that comes with the printer (146,57 Mb).
order a CD with the software to be mailed to you from the company.
The full software includes applications programs for things like scanning documents or images, and managing a
library of scanned images. Only the driver software, and not the full feature software, is needed to use the printer.
Again, most manufacturers have similar Websites. They want you to be able to use their products, which are
useless without the manual and the software drivers. They almost all also have simple quick start guides or getting
started booklets so you can set up their products without reading through the entire manual.
But how do you replace a missing cable? Simply buy a compatible USB cable from almost any consumer
electronics store, such as Best Buy or Radio Shack. If you are not sure which cable will work, then you can use
the model number to find a correct cable. You can also order the proper cable directly from the manufacturer, or
from online retailers like amazon.com or tigerdirect.com. The USB HP Photosmart printer has a type B connector
(shown back in Figure 5-8). Most USB printers have a similar type B connector.
5.2 Section Review
A. What is a driver. Do USB peripheral devices need
drivers?
B. Briefly describe how to connect a camera that
doesn't need a driver to a computer and move pictures
from the camera to the computer. What alternative
method can sometimes be used, and why doesn’t it
always work?
C. What three steps should someone always follow
when connecting a device that needs driver software,
such as a printer, to a computer? How can you tell if a
device needs a driver? Where can you find
replacement manuals and driver software?
—— § ——
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Section 5.3 – A Wireless Home Network with Internet Service
In this section we will look at wireless home network standards and hardware, how to set up the network, and
how to secure it from outside intrusion.
5. 3a Wireless Home Networks
Wireless home networks are becoming increasingly popular because they allows users to connect computers to
the Internet, to peripheral devices such as printers, and to other computers from almost any place in the home
without installing wires or cables. This is especially useful as laptop computers become more common, allowing
users to make the most of the laptop’s portability. Wireless home networks are also popular because they are less
expensive than wired networks, and easier to setup.
Most home computer networks are connected to and centered on the home’s broadband connection to the Internet,
which is often a telephone company DSL connection, a telephone company fiber optic connection, or a coaxial
cable television connection. Broadband networks are high speed networks that have special hardware allowing
data to move across the network more quickly. Broadband Internet connections, offered by companies like
Verizon and Comcast, are usually DSL, cable, or fiber optic connections accounting for most Internet access in
the US today, so we will focus on these.
Broadband and Dial-up Internet Access
in American Homes, 2000-2010
80%
70%
60%
50%
40%
30%
20%
10%
0%
2000
2001
2002
2003
2004
2005
Broadband
2006
2007
2008
2009
2010
Dial-up
Figure 5-15: The growth of home broadband Internet access in the United States. Broadband includes
DSL, cable and fiber optic connections.
data source: Pew Internet & American Life Project surveys
http://pewinternet.org/Reports/2010/Home-Broadband-2010.aspx
Dial-up telephone modem Internet access is becoming increasingly rare, so we will not cover that category. In the
Spring of 2010, for example, less than five percent of all Internet users in the U.S. had dial-up Internet access, as
shown in Figure 5-15.
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5.3c Wireless Networking Standards
The most important standards for wireless home networks are the IEEE’s 802.11 standards for wireless
telecommunication. (The standards are in section 802.11 of the IEEE’s telecommunications code.) Three
different standards are commonly used today for wireless home networks – IEEE 802.11b, 802.11g, and 802.11n.
All three will work, but the g and n standards work better over longer distances.
Standard
Max. Data Rate
Indoor Range
Outdoor Range
802.11 b
802.11 g
802.11 n
11 Mbps
54 Mbps
150 Mbps
125 ft
125 ft
230 ft
460 ft
460 ft
820 ft
Figure 5-16: Maximum data transfer rates and effective ranges for wireless
networking standards.
data source:
http://standards.ieee.org/getieee802/download/802.11-2007.pdf
5.3b Wireless Home
Network
Hardware
Almost all home computer networks and most networks in schools and the workplace use Ethernet technology.
Ethernet, defined by IEEE standard 802.3, is a networking standard defining cables .connections and protocols
for low cost local area networks. The hardware needed for a wireless home network includes a broadband modem,
a wireless router, and wireless network adapters for each computer or device connected to the network. Even
though it’s a wireless network, there are a few components wired together, most commonly using Ethernet
technology. So, you will also need at least two Ethernet cables, even though it’s called a wireless home network.
An Internet Service Provider will bring Internet service into your home through a broadband connection, usually a
DSL, coaxial cable, or fiber optic connection. The cable coming into the home is connected to an Ethernet
broadband modem, which is a device that changes the high speed signals used on a broadband network to
Ethernet signals compatible with data communication hardware for home computers. It is usually located in some
out of the way place, such as a basement or closet. The broadband modem is also called a DSL modem, coaxial
cable modem, or fiber optic modem, depending on the technology used on your Internet service provider’s
network. Modems change both the speed of the signal and the transmission media – for example, from a Verizon
coaxial cable to copper wiring in the home.
A router is an electronic device that routes data moving
across a network and between two networks. The router in a
home network is the electronic gateway between the Internet
service provider’s network and your home network. It routes
data between the two networks, making sure that each packet
of data is on its way to the correct destination with the right
addressing information for the receiving network. A wireless
router moves data between a wired network and a wireless
broadcast network.
Figure 5-17 shows two views of a Linksys E1000 wireless
router from Cisco. Most wireless routers for the home have
one port for a connection to the ISP’s broadband modem and
several connections for home devices that are wired directly
into the router. They can also transmit and receive signals to
communicate with wireless devices in the home. In this case,
the E1000 has a port with a yellow label for the connection to
the broadband modem, and four numbered ports with blue
labels for connections to devices in the home.
Figure 5-17: a Linksys E1000 wireless router.
Data Communications
Figure 5-18: RJ 45 connectors and an RJ-45
port on a laptop computer.
page 12
The ports on wireless routers use the standard connections
for Ethernet networking, called 8P8C (8 position 8 contact)
connectors or RJ-45 connectors. They are similar to the
standard RJ-11 telephone jacks found in most homes, but
slightly larger. Technically, RJ-45 is a particular wiring
standard defining how connectors with 8 positions and 8
contacts should be wired for a telephone system. The same
connectors are used in Ethernet technology, but wired
differently than the RJ-45 telephone wiring standard. Yet,
they are commonly called RJ-45 connectors rather than
8P8C connectors because they are exactly the same
connectors used in RJ-45 telephone jacks. Figure 5-18
shows two standard RJ-45 connectors and an RJ-45
Ethernet port on a common laptop computer.
The cables used for wired home networks and for the wired
connections in a wireless network are standard Ethernet
Category 5 or Category 6 cables, called cat-5 or cat-6
cables. They have 8 wires with RJ-45 connectors on each
end of the cable. Category 5 and Category 6 cables will
both work with common Ethernet technology, but Category
6 wiring is less subject to interference than Category 5
wiring, so it is more reliable and can handle a higher
bandwidth. Cat-6 is used for 1 gigabit per second Ethernet
networks, found in many businesses and schools. Most
home networks aren’t quite that fast. The Linksys E1000
wireless router shown above in Figure 5-17, for example,
operates at speeds up to 300 Mbps, or 0.3 gigabits per
second.
Figure 5-19: A cable for an Ethernet network
with RJ-45 connectors on each end.
For a home network, the broadband modem provided by the Internet service provider will need to be connected to
the wireless router using a cat-5 or cat-6 cable. It’s also necessary to connect a personal computer directly to the
wireless router using a cat-5 or cat-6 cable to initialize and program the router when setting up the network..
Of course, to plug your computer directly into an Ethernet port on the router, your computer will need to have an
Ethernet port as well. Almost all modern computers have at least one RJ-45 Ethernet port.
For wireless connections to the router, each device will
need to have a built-in wireless network adapter. A wireless
network adapter is a device with the electronic
components needed to transmit and receive data over a
wireless network. In essence, it is a specialized digital
radio. New laptop computers usually have built-in wireless
adapters.
Figure 5-20: An 802.11 g USB wireless adapter
from Netgear.
Computers that do not have built-in wireless adapters will
require a wireless adapter that can be plugged into the
computer. Today the easiest and most common way to do
this is by using an adapter that connects to the computer’s
USB port, and which looks very similar to a USB thumb
drive, like the one shown in Figure 5-20.
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Inexpensive printers are now available with built in wireless adapters. For example, the Lexmark Impact S305
and Epson Stylus® NX420 are all-in-one wireless printers that can each be purchased for less than $100.
Other devices, such as cell phones, alarm systems, and video game consoles, can also be connected to a wireless
network. Nintendo’s Wii game system, for example, comes with a built-in wireless adapter, and can easily be
connected to the Internet through your home’s wireless router.
Figure 5-21: Hardware in a typical wireless home network.
Figure 5-21 shows how all of this hardware for a wireless home network fits together. Your Internet service
provider’s network is connected to your home by a broadband modem. The modem is connected to an Ethernet
compatible wireless router using a cat-5 or cat-6 cable with RJ-45 connectors. Each computer on the wireless part
of the network connects to the router by using a wireless adapter. Other devices, such as a printer and a Nintendo
Wii game console, can also be connected if they have built-in wireless adapters.
5.3d Setting up a Wireless Home Network with Internet Service
Setting up a wireless home network is easier than you might think it is. Basically, you need to make sure that you
have the right equipment, that it is connected properly, and that it is properly initialized. The two trickiest things
to set up are the broadband modem, which connects your home to the Internet, and the wireless router. Your
Internet Service Provider should install and set up a broadband modem for you. That step is taken care of for you.
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So, to set up a wireless home network you will first need to locate your broadband modem or have one installed
by an Internet Service provider, then connect and initialize a wireless router. After that, the wireless devices in the
network should be able to connect to the router. You should also secure the network, which is discussed in the
next section of this chapter.
Setting up a wireless router requires you to connect the router to the broadband modem using an Ethernet cable.
You will also need to connect a computer directly to the router using a cable so that you can use the computer to
initialize the router. After the router is initialized, you can then disconnect the computer if you wish to do so, and
use it wirelessly.
Typically, routers have a control panel that is accessed through an Internet browser, such as Internet Explorer or
Firefox. After you connect the router, you must enter the router’s URL in the browser, then the control panel will
appear in the browser. You will need to use the control panel to do things like name the network and set up
network security. Except for network security, which is covered in the next section of this chapter, it shouldn’t be
too complicated. Yet, each router is slightly different and you may encounter things you have never seen before,
so, it is best to follow the same three step process used to set up a printer with a driver – 1. Find the directions. 2.
Read the directions 3. Follow the directions. Even experienced computer professionals who know what they are
doing will most likely still need the directions to find the router’s URL.
Almost all router manufacturers have a free help line you can call if you run into trouble setting up your router,
and the manuals for routers are available on the manufacturers’ Web sites, just like printer drivers are.
Computers with wireless adapters
should be able to detect the wireless
router and connect to it once it is set
up, but the first time each device
connects to the router, you may
need to make the connection
manually, using the operating
system’s connect to a network
feature. The following steps show
you how to do this in Windows 7.
The process is very similar in
Windows XP and Windows 8.0.
To connect a PC to a wireless
router:
1. Open the windows Control
Panel. This can be done from
the Windows start menu, as
shown in Figure 5-22. There
may a Connect To shortcut on
your system and there are other
ways to do this, but this way
should be available on every
computer with Windows.
Figure 5-22: The Windows 7 Start Menu, showing the link the
Control Panel.
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2. When the Control Panel opens, select Connect to the Internet under the Network and Internet heading, as
shown in Figure 5-23. In the figure, the Network and Internet links are also shown in a red box
Figure 5-23: The Connect to the Internet link 7 on the Windows Control Panel.
.
3. A Connect to the Internet window will appear, as shown on the left in Figure 5-24. Select Wireless and a
menu of the wireless routers your computer can detect will appear. This is shown on the right in Figure 5-24.
The router name and the network name are the same. Select your network. In the figure, the Office network
has been already selected.
4. A Connect automatically check box will appear asking if you wish to make this connection automatic in the
future. If you make the connection automatic, then the computer will connect to this network whenever it is
in range of the wireless router without you having to go through these steps. For now, you need to click the
Connect button to connect to the network.
Figure 5-24: The Connect to the Internet link 7 on the Windows Control Panel.
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5. If you have already set up security on your wireless
network, then a security window will appear, as shown
in Figure 5-25, asking yout to enter the network
security key. Once you enter the proper security key
and click OK, you will be connected to the network. If
the network has no security key, then you will be
connected without seeing this Window.
That’s it. It may take a minute or two for your router to
connect your computer to the Internet, but once that’s done
you are now ready to use your home network.
Setting up network security, including a network security
key is addressed in the next section.
Figure 5-25: the window asking you to enter
the network security key when connecting to a
wireless network.
5.3 Section Review
A. What are wireless home networks and why are they
popular?
B. Briefly describe the hardware needed for a wireless
home network.
C. What is the 802.11 standard? What versions of the
standard should be used for a wireless home network?
D. Briefly describe how to set up a wireless home
network. What can you do about computers that don't
have a built-in wireless adapter?
—— § ——
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Section 5.4 – Securing a Wireless Home Network
In this section we will look at the need to secure a wireless home network, the top five things you can do to secure
a wireless home network, and how to do so by reconfiguring a wireless router.
5.4a The Need to Secure a Wireless Home Network
As wireless home computer networks become increasingly popular, the need to secure them becomes increasingly
important. If you have an unsecured wireless network in your home, then your neighbors, people walking down
the street, or people driving by in cars may be able to connect to your network … unless your network is properly
secured.
Here are a few of the things that a person who is able to connect to your wireless network might do:

Slow down your Internet connection.

Steal data and files from your computer, including passwords, bank account information, credit card
details, photographs, and other personal private data.

Steal your identity.

Change the software on your computer.

Install viruses on your computer.

Send email, spam or viruses to other computers from your computer.

Use your computer as part of a denial of service attack on other computers.
These are just some of the risks of using an unsecure home network. In this lesson we will look at some fairly
easy things you can do to secure your wireless network, and then look at the process of configuring your router to
implement these security measures.
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5.4b Improving Wireless Home Security
Let’s list and describe several things that you can do in just a few minutes to make your wireless home network
more secure. Each of these involves configuring your wireless router, which is covered in the next section. So
here, in reverse order of importance, are the top five things you can do to configure your wireless network for
better security. Of course we won’t list things like ―don’t tell people your password‖ …
5. Use data encryption – This is what banks, credit card companies, and agencies like the FBI and CIA do to
protect data that is moving over a computer network. You can do the same thing on a home wireless network by
setting up an encryption method and an encryption key for your wireless router, and for any devices on your
network, including PCs and peripheral devices like printers. This is only number five in our list because
encryption schemes can be broken, so while it’s fifth in the list for keeping out professional hackers, it’s the
simplest and easiest way to protect data from casual users.
4. Don’t broadcast your network SSID – an SSID (Service Set
IDentifier) is the name of a network, or more precisely, the name of
the router controlling a network. When someone who has a computer
with a wireless adapter asks the computer to connect to a wireless
network, it will show a list of available networks. This list comes
from the wireless routers broadcasting their network SSIDs and
asking if anyone wants to connect to them. It’s like putting up an
electronic billboard that says ―Hey! This house has a network. Do
you want to try to connect to it?‖
You can stop this from happening by connecting to your router and
telling it not to broadcast the SSID. Then, anyone who wants to
connect to your network needs to know in advance that it’s there, and
what its name is.
Of course, once you stop broadcasting your SSID, then you will need
to tell each device that you want to connect to the network what the
network’s SSID is. You only need to do this once on each device that
is part of your network, so, you won’t have to type in the network
name every time you want to use the network, just the first time each
particular device connects to the network.
Figure 5-27: The names that appear
when someone attempts to connect
to a wireless network are each
network’s SSID.
3. Use your network adapters’ MAC addresses – A MAC address (Media Access Control address) is like a
serial number that is built into the hardware of each network adapter. The number is usually printed somewhere
on the adapter, or on the device if the adapter is built-in. You can give the router a list of MAC addresses, and
enable MAC addressing, which would only let the router connect with adapters you’ve listed. This isn’t foolproof
because MAC addresses themselves can be stolen and faked, but it goes a long way toward stopping things like
what’s shown in the Doonesbury comic strip above.
2. Disable remote router administration – Most routers have a feature that will allow someone to take control
of the router from another network by accessing it through your broadband connection. Your Internet service
provider or the router’s manufacturer may need to do this sometimes to diagnose and fix a problem with your
network. You should turn off this feature of your modem so that other people can’t log in and do the same
whenever they want to do so. You can turn it back on later if you actually do need remote help.
… and the number one thing you can do to protect your home network is:
1. Change the password on your wireless router – This is a big deal. If you leave your router’s password to be
the factory setting, then anyone familiar with that brand of router can actually log into the router and change your
network settings so that they, and not you, control the network in your home. They can actually take over your
computers while locking you out of the network. Again, this is a big deal. Changing your router’s password is one
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of the simplest and most important things you can do to secure your network. But, as with all passwords, don’t
lose it, or you may need to buy a new router.
5.4c Reconfiguring Your Router to Secure Your
Wireless Home Network
Now that you know what you can do to secure your wireless
home network, let’s look at how to actually do it. The first
and most important thing to know is that not all router
interfaces look the same, and this section provides a general
description of what to do, but the actual look of the screens,
buttons you need to press, and so on, are different from one
manufacturer to the next ... but only slightly. If you know
what to do and what to look for it is fairly easy to negotiate
the differences between router control panels, just as it’s
fairly easy to learn to drive most cars once you’ve learned
on one particular car.
Step 0 – Before you start. It helps to have a copy of the
manual or other documentation that came with your router,
because it will tell you exactly what to do. If you can’t find
it, then you can probably find it online by going to the
manufacturer’s Web site and searching for ―[the make and
model of your router] + documentation‖ or ―[the make and
model of your router] + manual‖.
Figure 5-28: a wireless security tab on the
control panel for a LinkSys wireless router.
Step 1. Access the router’s control panel. Once you have the documentation, you should connect to the router’s
internal software. This is easy to do because you use a Web browser to do so. Most routers will allow you to do
this from any brand of computer, sometimes even a cell phone, from almost any browser – Internet Explorer,
Firefox, Google Chrome, Safari, and so on. You won’t be connecting to the Internet, but will using the same
technology – a browser and an IP address – to connect your computer to the router.
Common Wireless Router
IP Addresses
Brand
3Com
Apple
AirLink+
Belkin
Dell
D-Link
Linksys
Microsoft
Netgear (since 2005)
US Robotic
IP Addresses
192.168.1.1
10.0.1.1
192.168.1.1
192.168.2.1
192.168.1.1
192.168.0.1
192.168.1.1
192.168.0.1
192.168.1.1
192.168.1.251
192.168.2.1
192.168.0.1
192.168.0.227
192.168.1.1
Figure 5-29: wireless router IP addresses
The image above shows the router control panel for a Cisco
Linksys router. Most router control panels are really just
web pages with tabs for different settings, text boxes, radio
buttons, etc. to configure the router. This image shows the
wireless encryption tab.
Each router has a ―home‖ IP address for your network. An
IP address is an Internet Protocol networking address. It is
like a numerical equivalent of a URL. URL’s like
www.ccp.edu are actually turned into IP addresses. To
connect to your router using a Web browser, you need to
open the browser and then type in the IP address of the
router as if it were a URL. The chart in Figure 5-29 shows
some common router IP addresses, but your router’s
manual is the best place to find your router’s IP address.
The browser will then probably ask you for the router’s
administrator login and password. Again this is in the
manual, unless, of course someone has changed it. If
anyone has changed it, then you need to know what it is
before continuing.
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After that, the router control panel will appear in the browser. You’ll be amazed at how fast this happens … this
is not some slow Internet connection; you are working with a device that is directly connected to your computer.
Step 2 – Set up data encryption. You can set up data encryption using WEP, WPA or other encryption methods.
The screen above shows settings for WEP encryption. WPA encryption is a newer more secure method, but WEP
is good enough to keep out all but dedicated professional hackers. Encryption methods can almost always be
broken by dedicated professionals, so by itself, this is only a small measure intended to keep out unwanted
nuisance intruders, so WEP is probably good enough. WEP can be set to 40/64 bit or 128 bit. If you’re not sure
what to do, then you should simply choose 40/64 bit encryption, enter a passphrase (if required), and then click
the button to generate one or more encryption keys. Write these down, because from now on you will need to use
one of them to set up a connection to your router from PC’s, etc. on your network.
Step 3– Turn off SSID Broadcasting. You’ll have to search around to find this setting, which could be on the
setup or administration tabs, but once you find it, it’s a simple matter of checking the box to ―turn off SSID
broadcasting‖. This will effectively prevent people from setting up a connection to your network unless they
know the network name in advance.
Step 4– Turn on the MAC filter. Usually there is a separate tab for this. If you look closely at the Linksys screen
above, you can see that it says “MAC Address Filter” in the second row of the menu bars at the top of the screen.
You’ll have to check a box to turn on MAC filtering, then type in the MAC addresses of the wireless adapters in
your network. The MAC addresses are usually printed on the Wi-Fi adapters or on a sticker on the computer if the
adapter is built into the computer. If you can’t find the MAC addresses, then do not turn on the MAC address
filter. Once you do turn it on and put in the MAC addresses, it works automatically. You can also come back and
change this later, for example, if you buy a new computer or Wi-Fi adapter.
Step 5 – Disable remote router administration. This is almost always just a simple check box on the
administration tab. You can turn it off then log in again to turn it on if you do someday need remote help.
Step 6 – Change the router’s login and password. This function could be on the setup or the administration tab,
and works pretty much the same as changing any login and password. This is a wise thing to do, as long as you
don’t lose the password. As mentioned above, changing your router’s password is one of the simplest and most
important things you can do to secure your network, but don’t lose the password.
That’s it. Don’t forget to save your changes when exiting the router control panel and to write down important
information, like encryption keys and the router’s new password. Most routers have a number of advanced
features beyond the scope of this course, and many have additional easy-to-use features like parental controls that
allow you to block certain Web sites.
5.4 Section Review
A. What are some of the things that a person who is
able to connect to your wireless network might do?
C. Briefly describe how to reconfigure a wireless
router to secure a home network.
B. List five things you can do to improve the security
of your wireless home network.
—— § ——
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page 21
Chapter 5 – Vocabulary
1. Define each of the following terms:
bit
Ethernet broadband modem
serial data communication
broadband network
Firewire
SSID
byte
IP address
byte-addressable memory
MAC address
Universal Serial Bus Implementers
Forum (USB-IF)
communications protocol
mobile computing devices
data bus
parallel data communication
data communication
peripheral device
data communication standards
RJ-45
driver
router
Ethernet
RS-232c
USB (Universal Serial Bus)
wireless network adapter
wireless router
word
word length
Chapter 5 – On the Web
For more information on the material on this chapter see the following Web sites:
Chapter 5 – Exercises
Exercise 1 – HP USB Printer
Create a Word document for this exercise listing your name, any other information your instructor directs you to
include, and the title HP C4480 Photosmart printer.
Find and open the setup guide for the HP C4480, as shown in the chapter. Copy into your word document the
URL for the Web page from which you can download the setup guide. Using Window’s print screen function,
copy an image of the screen showing the setup guide’s title page to a Word document. Add short notes describing
what the URL and image are.
Find the Web page for downloading the driver for the 32-bit Windows 7 operating system. Copy and paste the
URL for the Web page into your word document from part 1 of this question. Using Window’s print screen
function, copy a screen image of the page, and paste it into the Word document. Add short notes describing the
URL and what the image shows. Make sure your word document is neatly formatted and easy to understand.
Save the Word document for this exercise and submit it to your instructor. Make sure your name and any other
information the instructor requires are in the document.
Exercise 2 – Another USB Printer
In this assignment you will create a short word document describing how to find the manual and the driver
software for a particular printer other than the one shown in class. You must find the manual and driver software
for the printer n the Web.
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Select any common printer for a PC, such as:
Epson Artisan 810
Canon MX 330
Lexmark Interact S605
or a printer that you have at home or at work.
Create a short Word document listing the printer you choose.
Find the printer’s manual on the Web. Copy into your word document the URL for the Web page from which
you can download the setup guide. Open the manual and copy the cover page into your the Word document.
Find the Web page for downloading the driver for the printer for Windows 7 (32 bit). Copy the URL for the Web
page from which you can download the driver and paste it into your word document. Copy an image of the page
into a Word document using Window’s print screen function. Crop the image as necessary in Word.
Add some text to your document to briefly describe how to find the setup manual and the driver software for the
printer you have chosen, putting your two images in the correct location in the document. You may also add
other screen images if you would like, but keep it simple. Make sure your word document is neatly formatted and
easy to understand.
Save the Word document for this exercise and submit it to your instructor. Make sure your name and any other
information the instructor requires are in the document.
Note: Some of the manufacturers’ websites require you to select your country first, then re-direct you to their
USA website. All of their websites don't look the same, but they all have search boxes, and using your printer’s
model number you should be able to find the printer’s manual and its software. Some searches will take you to a
general Web page for the product. Look around the resulting page for a link to downloading, or for support.
Chapter 5 – Research Topics
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page 23
CCoonntteennttss
Chapter 5 Personal Computer Data Communications and Networking ....................................................................1
Section 5.1 – Serial Data Communications ............................................................................................................1
5.1a – Digital Data..............................................................................................................................................1
5.1b – Parallel and Serial Data Communication .................................................................................................2
5.1c – Serial Data Communication Protocols and Standards .............................................................................3
5.1d – RS-232c ...................................................................................................................................................3
5.1e – USB ..........................................................................................................................................................4
5.1f – Firewire ....................................................................................................................................................4
5.1 Section Review .............................................................................................................................................5
5.2a Using USB Technology ..............................................................................................................................5
5.2b Moving data from a camera over a USB Connection .................................................................................5
5.2c Connecting a USB Printer ..........................................................................................................................7
5.2 Section Review .............................................................................................................................................9
Section 5.3 – A Wireless Home Network with Internet Service ..........................................................................10
5. 3a Wireless Home Networks ........................................................................................................................10
5.3c Wireless Networking Standards................................................................................................................11
5.3b Wireless Home Network Hardware ..........................................................................................................11
5.3d Setting up Wireless Home Network with Internet Service .......................................................................13
5.3 Section Review ...........................................................................................................................................16
Section 5.4 – Securing a Wireless Home Network ..............................................................................................17
5.4a The Need to Secure a Wireless Home Network ......................................................................................17
5.4b Improving Wireless Home Security .........................................................................................................18
5.4c Reconfiguring Your Router to Secure Your Wireless Home Network ....................................................19
5.4 Section Review ...........................................................................................................................................20
Chapter 5 – Vocabulary ........................................................................................................................................21
Chapter 5 – On the Web .......................................................................................................................................21
Chapter 5 – Questions .......................................................................................... Error! Bookmark not defined.
Chapter 5 – Exercises ...........................................................................................................................................21
Exercise 1 – HP USB Printer............................................................................................................................21
Exercise 2 – Another USB Printer....................................................................................................................21
Chapter 5 – Research Topics ................................................................................................................................22
Topic 1 – Data Communications Standards ..................................................... Error! Bookmark not defined.

Chapter 5 Personal Computer Data Communications and Networking

Transcription

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