blackstartNetworking and Communications

Oct 26, 2013 (4 years and 8 months ago)



1. List and briefly describe the role of the three components used in any
communication system.

The three components used in any communication system are the transmitter, the medium
(something to carry the message) and a receiver.

2. What is
a network?

A network is a collection of computers and related devices such as printers and modems
that are connected to each other by some type of medium such as cables. The connections
between the devices allow them to communicate with each other and to s
hare programs
and data.

3. Name four basic services provided by a network.

The four basic services provided by a network involve sharing. Computers connected to a
network can communicate (share messages) with each other and they can share hardware,
s, and data.

4. What do the letters LAN stand for? List five different hardware components that
you might find connected to a LAN.

the letters LAN stand for Local Area Network. Five hardware components you might find
attached to a LAN are workstations (typ
ically personal computers), a file server, network
interface cards (NIC), cables and printers.

5. Define the term protocol. Include in your answer two different types of protocols
we discussed in class.

Protocols are a set of rules that governs communicati
ons. For example, when a modem
sends a message to another modem, the receiving modem must have some way to
determine that the message it received is the same as the message that was sent.
Connected modems use a variety of communication protocols to accompl
ish this. Two
protocols in use today are http, hypertext transport protocol and ftp, file transfer protocol.

6. What do the letters WAN stand for? List two ways a WAN differs from a LAN.

The letters WAN stand for wide area network. One major difference bet
ween the two
types of networks is the geographical area they serve. A LAN's service area is usually
confined to a room or one floor in a building while a WAN covers a much larger area
such as a city or a state, or, in the case of the Internet, the entire p
lanet. Another
difference between the two is the equipment that forms the network. A LAN is composed
of computers, printers and other types of equipment that would be commonly found in
any computer store. The components of a WAN are much more sophisticated

expensive and might include mainframe and mini computers, satellites, routers and fiber
optic cables.

7. Define the term client/server computing.

The term client/server computing refers to a type of network where a group of individual
terminals, the c
lients, share a connection to a central computer called a server. The server
provides processing power and storage to the clients.

8. How does a dumb terminal differ from an intelligent terminal?

There are two types of terminals you might find connected to

a server, dumb and
intelligent. A dumb terminal combines a keyboard and a monitor with a connection to a
server. A dumb terminal can display data received from a server but cannot change it in
any way. An intelligent terminal combines a keyboard and a mon
itor with a CPU, RAM
and usually storage too. Once connected to a server, an intelligent terminal receives data
from the server and can process and store that data independently of the server.

9. What is the role of a computer used as a file server?

A file

server is the central computer on a file server type LAN. It is dedicated to the role
of running the network. Some space on its large hard drive is made available to hold
programs and data files that can be accessed by the workstations connected to the
twork. The file server also contains most of the network operating system.

An important measure of a network's performance is response time. Response time is the
amount of time that elapses between a request for some type of service such as opening a
and when the service is actually provided. In large LANs, the number of requests for
service made on the file server can slow down response time. In order to reduce the
number requests the file server must handle, other types of servers (computers) are oft
connected to the network. One such type of server is a print server. A print server is a
computer attached to a network. A print server has one function, to handle all print
requests. Whenever a user prints a file, the print request is passed along to t
he print server
thus freeing the file server to handle other requests. Often there will be many files sent to
the print server for printing at the same time. The print server receives these requests and
lines them up (places them in a queue) in the order t
hey were received.

10. What are the two types of LANs we discussed? Briefly describe the differences
between the two types of LANs.

The letters LAN stand for local area network. There are two types of LANs, file server
and peer to peer. The two types of LA
Ns are distinguished by the presence of lack of a
central computer called a file server. A file server LAN has a central computer that is
used exclusively to provide for the needs of the network. This type of LAN gets its name
from this computer. The file
server is a central computer that is distinguished from other
computers attached to the network by its large hard drive and large amount of RAM. The
file server also contains the network operating system, the software program that in a
sense creates the ne
twork. The file server is not used by anyone for typical applications
such as word processing or email. Instead, it is used to provide storage and programs for
the workstations connected to it.

By contrast, a peer to peer LAN does not have a central comput
er. All computers
connected in a peer to peer LAN are used by one or more users as their personal
computer. Because the computers are connected to each other, the individual users can
still share hardware, programs and data.

There are advantages and disadv
antages to either type of LAN. A file server LAN allows
greater control of the network. With a file server LAN, often there is one person called
the network administrator who is responsible for seeing that the network is always
running. The net administrat
or also controls access to the network and other functions
such as maintaining network security and seeing that regular backup are performed.
Although the file server and administrator means added expense, having a central
computer and one person responsib
le for network make it more likely that tasks such as
maintaining network security and back up will be done.

Peer to peer networks are less expensive to create and maintain. For example, there is no
need to dedicate one computer as a file server. But becau
se there is no central control,
key functions such network security and backup are left to individual users and often go
undone. If security is not maintained or back up isn't performed regularly, the entire
network and its continued operation may be compr

11. Define the term topology. Include three different types of LAN topologies in
your answer.

The term topology refers to layout of the devices attached to a LAN and how the devices
are connected to each other. Three different network topologies ar
e bus, star and ring.

12. Name three types of cabling used to transmit information over a network.

Three types of cables used to carry signals over a network are twisted pair, coaxial and
fiber optics. Twisted pair and coaxial are both copper cables that c
arry electricity; fiber
optic cable is composed of strands of glass that carry light. Twisted pair cabling is similar
to the wire used to connect a telephone to a wall jack while coaxial cabling is similar to
the cable used to connect a TV or VCR to a cabl
e company's signal. Twisted pair is the
cheapest and easiest to install but also carries the smallest amount of information at a
time. Twisted pair is a common choice for small, peer to peer networks found in small
offices or homes. Coaxial cable, while mo
re expensive than twisted pair, also carries
more information and is commonly used for file server networks. Fiber optic cabling is
not used for LANs; it is too expensive. Fiber optics is used in WANs where large amount
of data are transmitted over long di
stances. Because fiber optic cables carry light instead
of electricity, the signal they carry is less susceptible to noise and other types of signal

13. List three differences between transmitting information over coaxial cable
versus using fi
ber optic cable.

Coaxial cable consists of copper wire; fiber optic cables consist of strands of glass.
Coaxial cable transmits electricity while fiber optic cables transmit electricity. Coaxial
cable transmits much less information at one time than fiber
optic cabling.

14. Define the term wireless communication. List two methods for transmitting data

Wireless communications is communications that take place without the use of cables.
Two types of wireless communication used by LANs are infrared

and radio frequency

15. What is the role of a network operating system? Include two examples of
network operating systems in your answer.

A network operating system plays a similar role for a network to the role an operating
system plays for an indi
vidual computer. The network operating system controls the flow
of information from one component of a network to another component. Whether it is a
request to print a file or start a program stored on the file server, it is the network
operating system th
at receives the request and sees that it is carried out properly. The
network operating system is found in two places, on the file server and the individual
workstations. Most of the network operating system is installed on the file server.
Individual work
stations only contain as much of the network operating system as they
need to make communicating with the network possible.

Examples of file server type operating systems are Netware from the company called
Novell and Windows NT from Microsoft. The Macinto
sh operating system and Windows
95 serve as both personal computer operating systems and as peer to peer network
operating systems.

16. Define the term login.

Logging in is the process of identifying yourself to the network for the purpose of gaining
s to the services provided by the network. Logging in usually involves entering a
username and a password.

17. What is a password? What are some precautions you should take to protect your

A password is a string of characters known only to the in
dividual user. The purpose of a
password is to identify a user at login time and to verify their identity.

Some precautions you can take to protect your password are:

Make it at least five characters long.

Never tell anyone your password.

Avoid writing i
t down but if you do write it down, don't keep it near your

Don't use common information about yourself such as your last name or your
birth date or the name of your dog. If you must use personal information, insert
random characters such as num
bers or punctuation marks in the information you

Don't use words from the dictionary.

Change your password regularly and don't use the same password for more than
one account.

18. What role does a modem play in the transmission of data?

s store information in a digital format. Most telephone lines carry analog
signals. In order to transmit digital information over analog telephone lines, the digital
information must be converted into an analog format. The role of a modem is to perform
s translation. The term modem is composed of parts of two words, mo from modulate
and dem from demodulate, mo dem. At the transmitting end of the communication link, a
modem modulates or changes digital information into a form that can be sent over phone
ines. At the receiving end, the other modem demodulates the incoming signal or changes
it from an analog signal back into a digital format.

19. How is the speed of a modem measured?

The speed of a modem is measured in bits per second (bps). Today's fastest

modems can
theoretically transmit data at 53,300 bps although telephone line conditions can
significantly reduce the actual transmission speed. To obtain a more meaningful measure
of a modem's speed, divide its bps rating by 10. The result is the number o
f character per
second the modem can transmit.

20. Define the terms uploading and downloading.

The term uploading means sending data from your computer to another computer that
you are connected to, typically by modem.

Downloading is the reverse of uploadi
ng. When you download, you are receiving data
from another computer and storing it on your computer.

21. Define the terms simplex, half duplex and full duplex.

Simplex communication involves a one way transfer of information. The transmitter
sends a messag
e but there is no way for the receiver to send a message back to the
transmitter using the same medium.

Half duplex communications involve two way transfer of information but only in one
direction at a time. The transmitter sends while the receiver accepts

the message. The two
components can change roles so that the receiver becomes the transmitter.

With full duplex communications, information can flow in both directions at the same

22. Give an example of simplex, half duplex and full duplex communica

Simplex: radio or TV.

Half duplex: CB radio or fax.

Full duplex: telephone or email

23. What do the letters ISDN stand for? List three differences between transmitting
data over ISDN lines and transmitting data over normal telephone lines.

The le
tters ISDN stand for integrated services digital network. ISDN is an all digital
phone connection. ISDN has several advantages over regular phone lines. Because ISDN
is an all digital connection, there is no need for a modem. However, you still need a piec
of hardware called a terminal adapter attached to your computer to send signals over the
ISDN lines. ISDN lines are faster than a POTS (plain old telephone service) line. While
today's fastest modems theoretically can transmit data at speeds of 53.3 Kbps

per second), in actuality their top speed is closer to 40 Kbps under ideal conditions.
Under less than ideal conditions (which is usually the case), top modem transmission
speeds are closer to 33.6 Kbps. By contrast, an ISDN line can transmit da
ta at 56 Kbps.
Since an ISDN line is actually two lines in one, it is often possible to combine the two
lines into one to achieve transmission speeds up to 128 Kbps. Also, because an ISDN line
is two lines in one, it is possible to transmit data and talk t
o someone at the same time.
Another benefit provided by an ISDN line is that all digital connections are less
susceptible to corruption of the transmitted data.

24. What is a T1 line? How does T1 differ from T3?

T1 and T3 refer to high speed digital servic
es offered by communications companies. The
difference between T1 and T3 lines is the amount of data they can carry in a given
amount of time.

T1 can carry up to 1.544 Mbps

T3 can carry up to 44.736 Mbps or approximately 28 times as much data as a T1

25. What do the letters DSL stand for? How does DSL differ from cable?

DSL and cable are examples of high speed (broadband) communications available for
small businesses and personal use at much more affordable prices than T1 or T3.

The letters DSL stan
d for digital subscriber line. DSL is a telephone connection that can
transmit data over existing phone lines up to 50 times faster than today's fastest modems.
Although cable can be even faster than DSL, because it is a type of party line, as more
in a local cable cluster use their connection, the slower everyone's service
becomes. Cable and DSL are not available in all areas of the country. The farther you get
from a large city, the less likely your chances of getting either type of service. Both t
of connection are priced competitively.