Name : Vincent Limonty
NIM : 1701310124
NIM : 1701310124
Students Assignments - Checkpoint
1. What Is the Purpose of the Components
Required for Successful Communications, and What Are Various Sending and
Receiving Devices?
Computer communications describes a process
in which two or more computers or devices transfer data, instructions, and information.
Today, even the smallest computers and devices can communicate directly with
one another, with hundreds of computers on a company network, or with millions
of other computers.
For successful communications, you need the
following:
• A sending device that initiates an
instruction to transmit data, instructions, or information.
• A communications device that connects the
sending device to a communications channel.
• A communications channel, or transmission
media on which the data, instructions, or information travel.
• A communications device that connects the
communications channel to a receiving device.
• A receiving device that accepts the
transmission of data, instructions, or information.
Some devices that serve as sending devices
and receiving devices are
(a) mainframe computers,
(b) servers,
(c) desktop computers,
(d) notebook computers,
(e) smart phones,
(f) Internet-enabled portable media
players,
(g) handheld game consoles, and
(h) GPS receivers.
The communications channel consists of
telephone and power lines, cable television and other underground lines,
microwave stations, and satellites.
2. How Are Computer Communications Used?
Computer communications are everywhere.
Many require that users subscribe to an Internet access provider. With other
computer communications, an organization such as a business or school provides
communications services to employees, students, or customers.
The following pages discuss a variety of
computer communications. Communications technologies include blogs, chat rooms,
e-mail, fax, FTP, instant messaging, newsgroups, RSS, video conferencing, VoIP,
Web, Web folders, and wikis. Users can send and receive wireless messages to
and from smart phones, cell phones, handheld game consoles, and other mobile devices
using text messaging, picture messaging and video messaging, and wireless
instant messaging. People connect wirelessly to the Internet through a wireless
Internet access point. A hot spot is a wireless network that provides Internet
connections to mobile computers and devices. A cybercafé is a coffeehouse,
restaurant, or other location that provides computers with Internet access. A
global positioning system (GPS) analyzes signals sent by satellites to
determine an earth-based receiver’s geographic location. Many software products
provide a means to collaborate, or work online with other users connected to a
server. Groupware is software that helps groups of people work on projects or
share information over a network.
Voice mail allows someone to leave a voice message
for one or more people. Web services describe standardized software that
enables programmers to create applications that communicate with other remote
computers.
3.What Are the Advantages of Using a
Network, and How Are LANs, MANs, and WANs Different?
a network is a collection of computers and
devices connected together via
communications devices and transmission media. Many businesses network their
computers together to facilitate communications, share hardware, share data and
information, share software, and transfer funds.
• Facilitating communications — Using a
network, people communicate efficiently and easily via e-mail, instant
messaging, chat rooms, blogs, wikis, online social networks, video telephone
calls, online meetings, video conferencing, VoIP, wireless messaging services,
and groupware.
• Sharing hardware — In a networked
environment, each computer on the network can have access to hardware on the
network. Business and home users network their hardware to save money.
• Sharing data and information — In a
networked environment, any authorized computer user can access data and
information stored on other computers on the network.
• Sharing software — Users connected to a
network have access to software on the network.
To support multiple users’ access of
software, most vendors sell network versions or site licenses of their
software, which usually cost less than buying individual copies of the software
for each computer.
• Transferring funds — Called electronic
funds transfer (EFT ), it allows users connected to a network to transfer money
from one bank account to another via transmission media.
LANs,
MANs, and WANs
Networks usually are classified as a local
area network, metropolitan area network, or wide area network. The main differentiation
among these classifications is their area of coverage.
· LAN (local area network) is a network that
connects computers and devices in a limited geographical area such as a home,
school computer laboratory, office building, or closely positioned group of
buildings. Each computer or device on the network, called a node, often shares
resources such as printers, large hard disks, and programs.Often, the nodes are
connected via cables.
· MAN (metropolitan area network) is a high-speed
network that connects local area networks in a metropolitan area such as a city
or town and handles the bulk of communications activity across that region. A
MAN typically includes one or more LANs, but covers a smaller geographic area
than a WAN. A MAN usually is managed by a consortium of users or by a single
network provider that sells the service to the users. Local and state
governments, for example, regulate some MANs. Telephone companies, cable
television operators, and other organizations provide users with connections to
the MAN.
· WAN (wide area network) is a network that covers
a large geographic area (such as a city, country, or the world) using a
communications channel that combines many types of media such as telephone
lines, cables, and radio waves (Figure 9-12). A WAN can be one large network or
can consist of two or more LANs connected together. The Internet is the world’s
largest WAN.
4.How Are a Client/Server and
Peer-to-Peer Network Different, and How Does a P2P Network Work?
· Client/Server
On a client/server network, one or more computers act as a server, and
the other computers on the network request services from the server. A server,
sometimes called a host computer, controls access to the hardware, software,
and other resources on the network and provides a centralized storage area for
programs, data, and information. The clients are other computers and mobile
devices on the network that rely on the server for its resources. For example,
a server might store a database of customers. Clients on the network (company
employees) access the customer database on the server.
· Peer-to-Peer
One type of peer-to-peer network is a simple, inexpensive network that
typically connects fewer than 10 computers. Each computer, called a peer, has
equal responsibilities and capabilities, sharing hardware (such as a printer),
data, or information with other computers on the peer-to-peer network. Each
computer stores files on its own storage devices. Thus, each computer on the
network contains both the server operating system and application software. All
computers on the network share any peripheral device(s).attached to any
computer. For example, one computer may have a laser printer and a scanner,
while another has an ink-jet printer and an external hard disk. Peer-to-peer networks
are ideal for very small businesses and home users.
· Another type of peer-to-peer, called P2P,
describes an Internet network on which users access each other’s hard disks and
exchange files directly over the Internet. This type of peer-to peer network sometimes
is called a file sharing network because users with compatible software and an
Internet connection copy files from someone else’s hard disk to their hard
disks. As more users connect to the network, each user has access to shared
files on other users’ hard disks. When users log off the network, others no
longer have access to their hard disks.
5.How Are a Star Network, Bus Network,
and Ring Network Different?
· Star Network
On a star network, all of the computers and devices (nodes) on the
network connect to a central device, thus forming a star. Two types of devices
that provide a common central connection point for nodes on the network are a
hub and a switch. All data that transfers from one node to another passes
through the hub or switch. Star networks are fairly easy to install and
maintain. Nodes can be added to and removed from the network with little or no
disruption to the network. On a star network, if one node fails, only that node
is affected. The other nodes continue to operate normally. If the hub or switch
fails, however, the entire network is inoperable until the device is repaired.
Most large star networks, therefore, keep backup hubs or switches available in
case the primary one fails.
· Bus Network
A bus network consists of a single central cable, to which all computers
and other devices connect. The bus is the physical cable that connects the
computers and other devices. The bus in a bus network transmits data,
instructions, and information in both directions. When a sending device
transmits data, the address of the receiving device is included with the
transmission so that the data is routed to the appropriate receiving device.
Bus networks are popular on LANs because they are inexpensive and easy to
install. One advantage of the bus network is that computers and other devices
can be attached and detached at any point on the bus without disturbing the
rest of the network.
· Ring Network
On
a ring network, a cable forms a closed loop (ring) with all computers and
devices arranged along the ring. Data transmitted on a ring network travels
from device to device around the entire ring, in one direction. When a computer
or device sends data, the data travels to each computer on the ring until it
reaches its destination. If a computer or device on a ring network fails, the
entire network potentially could stop functioning. A ring network can span a
larger distance than a bus network, but it is more difficult to install. The
ring topology primarily is used for LANs, but also is used in WANs.
6.What Are Various Network
Communications Standards?
A network standard
defines guidelines that specify the way computers access a medium, the type(s)
of medium, the speeds on different types of networks, and the type of physical
cable or wireless technology used. Network communications standards include the
following. Ethernet specifies that no central computer or device on the network
should control when data can be transmitted. Token ring requires devices to
share or pass a special signal, called a token. TCP/IP divides data into
packets. Wi-Fi identifies any network based on the 802.11 standards for
wireless communications. Bluetooth uses
short-range radio waves to transmit data. UWB specifies how two UWB devices use
short-range radio waves to communicate at high speeds. IrDA transmits data
wirelessly via infrared light waves. RFID uses radio signals for
communications. WiMAX is a network standard developed by IEEE that specifies how
wireless devices communicate over the air in a wide area. The Wireless
Application Protocol (WAP) specifies how some mobile devices can display
Internet content.
7.What Is the Purpose of Communications
Software?
Communications software consists of
programs that (1) help users establish a connection to another computer or
network; (2) manage the transmission of data, instructions, and information;
and (3) provide an interface for users to communicate with one another. The
first two are system software and the third is application software. Chapter 3
presented a variety of examples of application software for communications:
e-mail, FTP, Web browser, newsgroup/message boards, chat rooms, instant
messaging, video conferencing, and VoIP. Sometimes, communications devices are
preprogrammed to accomplish communications tasks. Other communications devices
require separate communications software to ensure proper transmission of data.
Communications software works with the network standards and protocols just
discussed to ensure data moves through the network or the Internet correctly.
Communications software usually is bundled with the operating system or
purchased network devices. Communications software helps users establish a
connection to another computer or network; manages the transmission of data,
instructions, and information; and
provides an interface for users to communicate with one another.
8.What Are Various Types of Lines for
Communications over the Telephone Network?
· Dial-Up Lines
A dial-up line is a temporary connection that uses one or more analog
telephone lines for communications. A dial-up connection is not permanent. a
dial-up line to connect computers costs no more than making a regular telephone
call.
· Dedicated Lines
Satellite local access area local telephone company A dedicated line is a
type of always on connection that is established between two communications
devices (unlike a dial-up line where the connection is reestablished each time
it is used). The quality and consistency of the
connection on a dedicated line are better than a dial-up line because
dedicated lines provide a constant connection. Businesses often use dedicated
lines to connect geographically distant offices. Dedicated lines can be either
analog or digital. Digital lines increasingly are connecting home and business
users to networks around the globe because they transmit data and information
at faster rates than analog lines. Five types of digital dedicated lines are
ISDN lines, DSL, FTTP, T-carrier lines, and ATM.
· ISDN Lines
For the small business and home user, an ISDN line provides faster
transfer rates than dial-up telephone lines. Not as widely used today as in the
past, ISDN (Integrated Services Digital Network) is a set of standards for
digital transmission of data over standard copper telephone lines. With ISDN,
the same telephone line that could carry only one computer signal now can carry
three or more signals at once through the same line, using a technique called
multiplexing.
· DSL
DSL is a popular digital line alternative for the small business or home
user. DSL (Digital Subscriber Line) transmits at fast speeds on existing
standard copper telephone wiring.
Some DSL installations include a dial tone, providing users with both
voice and data communications. These DSL installations often require that
filters be installed to reduce noise interference when voice communications
share the same line. ADSL is one of the more popular types of DSLs. As shown in
Figure 9-25, ADSL (asymmetric digital subscriber line) is a type of DSL that
supports faster transfer rates when receiving data (the downstream rate) than
when sending data (the upstream rate). ADSL is ideal for Internet access
because most users download more information from the Internet than they
upload.
· FTTP
FTTP, which stands for Fiber to the Premises, uses fiber-optic cable to
provide extremely high-speed Internet access to a user’s physical permanent
location. Two specific types of FTTP are FTTH and FTTB. FTTH (Fiber to the
Home) provides home users with Internet access via fiber-optic cable.
Similarly, FTTB (Fiber to the Building) refers to small businesses that use
fiber-optic cables to access the Internet. With FTTP service, an optical
terminal at your location receives the signals and transfers them to a router
connected to your computer. As the cost of installing fiber decreases, more
homes and businesses will opt for this high-speed Internet access.
· T-Carrier Lines
A T-carrier line is any of several types of long-distance digital
telephone lines that carry multiple signals over a single communications line.
Where as a standard dial-up telephone line carries only one signal, digital
T-carrier lines use multiplexing so that multiple signals share the line.
T-carrier lines provide very fast data transfer rates. Only medium to large
companies usually can afford the investment in T-carrier lines because these
lines are so expensive.
· ATM
ATM (Asynchronous Transfer Mode) is a service that carries voice, data,
video, and multimedia at very high speeds. Telephone networks, the Internet,
and other networks with large amounts of traffic use ATM. Some experts predict
that ATM eventually will become the Internet standard for data transmission,
replacing T3 lines.
9.What Are Commonly Used Communications
Devices?
A communications device is hardware capable
of transmitting data between a sending device and a receiving device. A dial-up
modem converts digital signals to analog signals and analog signals to digital
signals. So that data can travel along analog telephone lines. A digital modem
sends and receives data and information to and from a digital line. An ISDN
modem transmits digital data to and from an ISDN line, while a DSL modem
transmits digital data to and from a DSL line. A cable modem, sometimes called
a broadband modem, is a digital modem that sends and receives digital data over
the cable television network. A wireless modem uses the cell phone network to
connect to the Internet wirelessly from mobile computers and devices. A network
card enables a computer or device that does not have built-in networking
capability to access a network. A wireless access point allows computers and
devices to transfer data wirelessly. A router connects multiple computers or
other routers together and transmits data to its correct destination on the
network. A hub or switch is a device that provides a central point for cables
in a network.
10. How
Can a Home Network Be Set Up?
A home network connects multiple computers
and devices in a home. An Ethernet network connects each computer to a hub with
a physical cable. A home power line cable network uses the same lines that
bring electricity into the house. A phone line network uses existing telephone
lines in a home. Most home networks use a Wi-Fi network.
11.What
Are Various Physical and Wireless Transmission Media?
· Twisted-Pair Cable
One of the more widely used transmission media for network cabling and
telephone systems is twisted-pair cable. Twisted-pair cable consists of one or
more twisted-pair wires bundled together. Each twisted-pair wire consists of
two separate insulated copper wires that are twisted together. The wires are
twisted together to reduce noise. Noise is an electrical disturbance that can
degrade communications.
· Coaxial Cable
Coaxial cable, often referred to as coax (pronounced KO-ax), consists of
a single copper wire surrounded by at
least three layers: (1) an insulating material, (2) a woven or braided metal,
and (3) a plastic outer coating (Figure 9-37). Cable television (CATV) network
wiring often uses coaxial cable because it can be cabled over longer distances
than twisted-pair cable. Most of today’s computer networks, however, do not use
coaxial cable because other transmission media such as fiber-optic cable
transmit signals at faster rates.
· Fiber-Optic Cable
The core of a fiber-optic cable consists of dozens or hundreds of thin
strands of glass or plastic that use light to transmit signals. Each strand,
called an optical fiber, is as thin as a human hair. Inside the fiber-optic
cable, an insulating glass cladding and a protective coating surround each
optical fiber. Fiber-optic cables have the following advantages over cables
that use wire, such as twisted-pair and coaxial cables:
• Capability of carrying significantly more signals than wire cables
• Faster data transmission
• Less susceptible to noise (interference) from other devices such as a
copy machine
• Better security for signals during transmission because they are less
susceptible to noise
• Smaller size (much thinner and lighter weight)
· Broadcast radio distributes radio signals
through the air over long and short distances.
· Cellular radio is a form of broadcast radio that
is used widely for mobile communications.
· Microwaves are radio waves that provide a high
speed signal transmission.
· A communications satellite is a space station
that receives microwave signals from an earth-based station, amplifies the
signals, and broadcasts the signals back over a wide area.
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