COMMUNICATIONS,
NETWORKS, & SAFEGUARDS
The Wired & Wireless World
Chapter Topics & Key Questions
6.1 From the Analog to the Digital Age How do digital data and
analog data differ, and what does a modem do?
6.2 Networks What are the benefits of networks, and what are their
types, components, and variations?
6.3 Wired Communications Media What are types of wired
communications media?
6.4 Wireless Communications Media What are types of wireless
communications media, both long distance and short distance?
6.5 Cyberthreats, Hackers, & Safeguards What are areas I should be
concerned about for keeping my computer system secure?
6.1 FROM THE ANALOG TO THE DIGITAL AGE
How do digital data and analog data differ, and what does a modem
do?
The Digital Basis of Computers: Electrical Signals as
Discontinuous Bursts
What does “digital” mean?
Digital describes any system based on discontinuous data or
events; in the case of computers, it refers to communications
signals or information represented in a two-state (binary)
way using electronic or electromagnetic signals. Each 0 and
1 signal represent a bit.
The Analog Basis of Life: Electrical Signals as Continuous Waves
What does “analog” mean?
Analog relates to using signals or information represented by
a continuously variable physical quantity such as spatial
position, voltage, etc.
Purpose of the Dial-Up Modem: Converting Digital Signals to Analog
Signals & Back
How does a telephone modem change analog to digital signals and
the reverse?
Modems (modulators/demodulators) are data communication
devices that convert digital signals to analog signals, and
vice versa.
An analog–to–digital converter (ADC, A/D, or A-to-D) is a
system that converts an analog signal, such as a sound picked
up by a microphone or light entering a digital camera, into
a digital signal.
While the digital-to-analog conversion (DAC), process by
which digital signals (which have a binary state) are
converted to analog signals (which theoretically have
an infinite number of states). For example, a modem converts
computer digital data to analog audio–frequency signals that
can be transmitted over telephone lines.
6.2 NETWORKS
Network
A network is a communication between two or more computer
devices means when two or more devices are connected to each
other for the purpose of communication is called network. So
essentially, network consist of two or more computers to share
resources, exchange files or allow electronic communications.
The Benefits of Networks
What are five ways I might benefit from networks?
1. SHARING OF PERIPHERAL DEVICES – such as printers, scanners,
disk drives.
2. SHARING OF PROGRAMS & DATA – less expensive.
3. BETTER COMMUNICATIONS – use other communication program.
4. SECURITY OF INFORMATION – backup critical information because
it is stored centrally.
5. ACCESS TO DATABASES – Networks enable users to tap into
numerous databases.
Types of Networks: WANs, MANs, LANs, HANs, PANs, & Others
Types of Networks
LOCAL AREA NETWORK (LANs). It is used in local areas means it
is a small network that covers small areas like an office,
school, college, building etc. Uses of Local Area Network are
the following: LAN are mostly used in business where all
business data stores in serves; This can be used in factories;
This can be used in schools and colleges where all the
students, teachers, staff all the data store in servers; and,
This network can also be used in our homes where all the
computers, mobiles, printers are connected to the routers,
and these devices can exchange data.
METROPOLITAN AREA NETWOR (MANs). It is a network which is
bigger than the local area network. MAN is used in larger
areas than LANs. For example, a business company has many
branches in different locations and every branch uses a LAN.
WIDE AREA NETWORK (WANs). Meaning this network is used in
large geographical areas like in the whole country or
continent and uses common carriers like – satellite,
telephone line, etc. when many LANS and MANS networks are
connected to each other for the purpose of communication then
it’s become WAN because now the area of the network is too
wide so it is called a wide area network. This network
generally covers larger distance areas (like states,
countries, and continents). Actually, when you are reading
articles on the internet which is the largest WAN in the
world, where thousands of LAN and MAN connected to each other.
HOME AREA NETWORK. A home area network (HAN) uses wired,
cable, or wireless connections to link a household’s digital
devices.
PERSONAL AREA NETWORK. Meaning it is the smallest network
which is very personal to a user. This network use in the
personal space of a person that’s why this network name is a
personal area network. This normally ranges within around 10
meters.
HOME AUTOMATION NETWORK. A home automation network relies on
very inexpensive, very short-range, low-power wireless
technology in the under 200-Kbps range to link switches and
sensors around the house.
How Networks Are Structured: Client/Server & Peer to Peer
How Networks Are Structured:
1. Client/Server – a client/server network consists of
clients, which are microcomputers that request data, and servers,
which are computers used to supply data. Network mostly used in
business organizations where central servers are used and all the
business data stored in a server. All the clients computers are
connected to the central server where they can access data from
the server.
2. Peer to Peer – In a peer–to-peer (P2P) network, all
microcomputers on the network communicate directly with one
another without relying on a server. Networks are mostly used in
homes where all computers are connected to each other and can
exchange data with each other without server.
Intranets, Extranets, & VPNs
What are the differences among Intranets, Extranets, and VPNs?
INTRANETS: FOR INTERNAL USE ONLY
An intranet is an organization’s internal private network
that uses the infrastructure and standards of the internet
and the web. Many businesses now build internal
networks (more commonly known as an intranet) to store
information on a central system at a private internet address,
accessible only by their employees.
EXTRANETS: FOR CERTAIN OUTSIDERS
An extranets are private intranets that connect not only
internal personnel but also selected suppliers and other
strategic parties. For example, a business can let clients
track the progress of their orders, and the payment of
suppliers online can be linked directly to the business
accounts system.
VIRTUAL PRIVATE NETWORKS (VPNs)
A virtual private networks ( VPNs), private networks that use
a public network (usually the internet) to connect remote
sites. A virtual private network or VPN allows the user to
connect across the internet to the business’ private network.
It creates a secure link between the remote worker’s computer
and the central system. A VPN can be cheaper to use than
leased lines or domestic–type broadband connections.
Components of a Network
What are the various parts of a network?
COMPUTER NETWORK
A computer network is build up from several components,
hardware and software alike. Regardless of size, networks all
have several components in common. These components together
makes it possible to transfer data from one device to another
and makes smooth communication between two or more devices.
WIRED AND/ OR WIRELESS CONNECTIONS. A network uses either wired or
wireless connection system. Wired networks use cables like
twisted-pair cable, coaxial cable, or fiber optic cable to connect
devices, such as laptop or desktop computers, to the Internet or
another network. On the other hand, wireless networks allow devices
to stay connected to the network but roam untethered to any wires.
Access points amplify signals, so a device can be far from a router
but still be connected to the network. These signals may come from
infrared, microwave (such as Bluetooth), broadcast radio (such as
Wi–Fi), or from a satellite.
HOSTS AND NODES. Host is a device that is linked to a particular
network, it may work as a server that offers applications to
devices and users. A host may also play the role of the client on
a network. And because it is a host computer, it can control the
network. Node is the communication endpoint, it is any network–
attached addressable computer. Basically, it is a computer in a
network.
PACKETS. Packets are small segments of a larger message.
Essentially, the data sent over computer or communications
networks (such as the internet), is divided into packets. These
packets are then recombined by the computer or device that receives
them to appear just like the original data before it was
transmitted.
PROTOCOLS. Fundamentally, protocols allow connected devices to
communicate with each other, regardless of any differences in their
internal processes, structure or design. It is possible because
they are established set of rules that determine how data is
transmitted between different devices in the same network. Network
protocols are the reason you can easily communicate with people
all over the world, and thus play a critical role in modern digital
communications. Every device connected to a network has an internet
protocol (IP) address so that other computers on the network can
properly route data to that address. Sending and receiving devices
must follow the same set of protocols.
NETWORK LINGKING DEVICES: HUBS, SWITCHES, BRIDGES, GETAWAYS,
ROUTERS AND BACKBONES
NETWORK LINGKING DEVICES.
Hardware devices that are used to connect computers and other
electronic devices to a network are called network devices or
network linking devices. These devices transfer data in a
fast, secure and correct way over the same or different
networks. Network devices may be inter–network or intra–
network. Some devices are installed on the device, like NIC
card or RJ45 connector, whereas some are part of the network,
like router, switch, etc. They are also used to link together—
LANs to MANs and MANs to WANs.
• HUBS are hardware devices that divides the network connection
among multiple devices. Meaning, they are a central point
where data arrives from one or more directions. And after
they arrive, they are then forwarded towards another set of
directions because they contain multiple ports. However, it
is a half-duplex device which transmits data in both
directions but only in one direction at a time and the
bandwidth is shared by all components.
• SWITCHES are devices that connects computers to a network
just like hubs. They are full-duplex devices which allow them
to transmit data back and forth at the same time and this
greatly enhance the performance and sped of the network.
Additionally unlike its counterpart, a switch allows each
component full use of the bandwidth.
• BRIDGES connect multiple LANs (local area networks) that has
similar protocols to form a larger LAN. And this process is
