Chapter 7: Networking and Security
7.1 Networking Fundamentals
A network is a computer system that uses communication equipment to connect two or
more computers and their resources. In other words, a network is an interconnected
system of computers, terminals, and communications channels and devices. Networking
includes local area networks (LAN) which are designed to share data and resources
among several individual computer users in an office or building.
The basic components for networking consists of communication system used to
transmit the messages are (1) a sending device (2) a communication channel, and (3) a
receiving device. A communication network is any arrangement where a sender
transmits a message to a receiver over a channel consisting of some type of medium
(communication channel). Figure 7.1 illustrates a simple conceptual model of a
telecommunication network, which shows that it consists of five basic categories of
components.
Telecommunication
Processors
PCs, NCs and
other
terminals
Telecommunications
channels
Telecommunication
Processors
Computers
Figure 7.1: The five basic components for telecommunications network

Terminals, such as networked personal computers, network computers, or
information appliances. Any input/output device that use telecommunication
networks to transmit or receive data is a terminal, including telephones and the
various computer terminals.

Telecommunications processors, which support data transmission and reception
between terminals and computers. These devices, such as modems, switches,
and routers, perform a variety of control and support functions in a
telecommunications network. For example, they convert data from digital to
analog and back, code and decode data, and control the speed, accuracy, and
efficiency of the communications flow between computers and terminals in a
network.

Telecommunications channels over which data are transmitted and received.
Telecommunications channels may use combinations of media, such as copper
wires, coaxial cables, or fiber-optic cables, or use wireless systems like
microwave, communications satellite, radio, and cellular systems to interconnect
the other components of a telecommunications network.

Computers of all sizes and types are interconnected by telecommunications
networks so that they can carry out their information processing assignments.
For example, a mainframe computer may serve as a host computer for a larger
network, assisted by a midrange computer serving as a front-end processor,
while a microcomputer may act as a network server in a small network.

Telecommunications control software consists of programs that control
telecommunications activities and manage the functions of telecommunications
networks. Examples include network management programs of all kinds, such as
a telecommunications monitors for mainframe host computers, network
operating systems for network servers, and Web browsers for micro-computers.
7.2 Network Architectures and Protocols
Network Architecture. The goal of network architectures is to promote an open, simple,
flexible, and efficient telecommunications environment. This is accomplished by the use
of standard protocols, standard communications hardware and software interfaces, and
the design of a standard multilevel interface between end users and computer systems.
Protocols. A protocol is a standard set of rules and procedures for the control of
communications in a network. However, these standards may be limited to just one
manufacturer’s equipment, or to just one type of data communications. Part of the goal
of communication network architecture is to create more standardization and
compatibility among communication protocols. One example of a protocol is a standard
for the physical characteristics of the cables and connectors between terminals,
computers, modems, and communication lines. Other examples are the protocols that
establish the communication control information needed for handshaking which is the
process or exchanging predetermined signals and characters to establish a
telecommunications session between terminals and computers. Other protocols deal
with control of data transmission reception in a network, switching techniques,
internetwork connections, and so on.
The OSI Model. The International Standards Organization (ISO) has developed a sevenlayer Open Systems Interconnection (OSI) model to serve as a standard model for
network architectures. Dividing data communications functions into seven distinct
layers promotes the development of modular network architectures, which assists the
development, operation, and maintenance of complex telecommunications networks.
Figure 7.2 illustrates the functions of the seven layers of the OSI model architecture.
The Internet’s TCP/IP. The Internet uses a system of telecommunications protocols that
has become so widely used that it is equivalent to a network architecture. The Internet’s
protocols suite is called Transmission Control Protocol/Internet Protocol and is known as
TCP/IP. As figure 7.2 shows, TCP/IP consists of five layers of protocols that can be
related to the seven layers of the OSI architecture. TCP/IP is used by the Internet and by
all intranets and extranets. Many companies and other organizations are thus
converting their client/server networks to TCP/IP technology, which are commonly
known as IP networks.
TCP/IP
Application for
Process Layer
Application
Layer
Provides communications services for
end user applications
Presentation
Layer
Provides appropriate data
transmission formats and codes
Session
Layer
Support the accomplishment of
telecommunications sessions
Host-to-Host
Transport Layer
Transport
Layer
Supports the organization and
transfer of data between nodes in
the network
Internet Protocol (IP)
Network
Layer
Provides appropriate routing by
establishing connections among
network links
Network Interface
Data Link
Layer
Supports error-free organization
and transmission of data in the
network
Physical Layer
Physical
Layer
Provides physical transmission of
data on the telecommunications
media in the network
Figure 7.2: The seven layers of the OSI communications network architecture,
and the five layers of the Internet’s TCP/IP protocol suite
7.3 Type of Communications Networks
Many different types of networks serve as the telecommunications infrastructure for
the Internet, intranets and extranets. However, from the end user’s point of view, there
are only a few basic types, such as wide area and local area networks and client/server,
network computing, and peer-to-peer networks.
Wide Area Network. Telecommunications networks covering a large geographic area
are called wide area network (WAN) (figure 7.3a). Networks that cover a large city or
metropolitan area (metropolitan area networks) can also be included in this category.
Such large networks have become a necessity for carrying out the day-to-day activities
of many business and government organizations and their end users. For example,
WANs are used by many multinational companies to transmit and receive information
among their employees, customers, suppliers, and other organizations across cities,
regions, countries and the world.
Figure 7. 3 (a) Wide Area Network
(b) Local Area Network
Local Area Networks. Local Area Networks (LANs) connects computers and other
information processing devices within a limited physical area, such as an office,
classroom, building, manufacturing plant, or other work site (figure 7.3b). LANs have
become commonplace in many organizations for providing telecommunications
network capabilities that link end users in offices, departments and other workgroups.
LANs use a variety of telecommunications media, such as ordinary telephone wiring,
coaxial cable, or even wireless radio and infrared system, to interconnect
microcomputer workstations and computer peripherals. To communicate over the
network, each PC usually has a circuit board called a network interface card. Most LANs
use a more powerful microcomputer having a large hard disk capacity, called a file
server or network server, that contains a network operating system program that
controls telecommunications and the use and sharing of network resources. For
example, it distributes copies of common data files and software packages to the other
microcomputers in the network and control access to shared laser printers and other
network peripherals.
Virtual Private Networks. Most organizations use Virtual Private Networks (VPNs) to
establish secure intranets and extranets. A virtual private networks is a secure network
that uses the Internet as its main backbone network but relies on the fire walls and
other security features of its Internet and intranet connections and those of
participating organizations (figure 7.4a). Thus, for example, VPNs would enable a
company to use the Internet to establish secure intranets between its distant branch
offices and the manufacturing plants, and secure extranets between itself and its
customers and suppliers. Virtual private networks (VPN) provide an encrypted
connection between a user's distributed sites over a public network (e.g., the Internet).
By contrast, a private network uses dedicated circuits and possibly encryption. This page
describes IP-based VPN technology over the Internet, though an organization might
deploy VPN's on its internal nets (intranets) to encrypt sensitive information. The basic
idea is to provide an encrypted IP tunnel through the Internet that permits distributed
sites to communicate securely. The encrypted tunnel provides a secure path for network
applications and requires no changes to the application.
Client/Server Networks. Client/server networks have become the predominant
information architecture of enterprise wide computing. Client/server network consists
of one powerful computer that coordinates and supplies to all other nodes on the
network. Server nodes coordinate and supply specialized services, and client nodes
request the services. In a client/server networks, end-user PC or NC workstations are
the clients. They are interconnected by local area networks and share application
processing with network servers, which also manage the networks (figure 7.4b). This
arrangement of clients/servers is sometimes called two-tier client/server architecture.
Local area networks are also interconnected to other LANs and WANs of client
workstations and servers.
Figure 7.4 (a) Virtual Private Networks
(b) Client/Server Networks.
A continuing trend is the downsizing of larger computer systems by replacing them with
client/server networks. For example, a client/server network of several interconnected
LANs may replace a larger mainframe-based network with many end user terminals
(figure 7.5). This typically involves a complex and costly effort to install new applications
software that replaces the software of older, traditional mainframe-based business
information systems, now called legacy systems. Client/server networks are seen as
more economical and flexible than legacy systems in meeting end user, workgroup, and
business unit needs, and more adaptable in adjusting to a diverse range of computing
workloads.
Servers
Client system
Types: PCs, Network
computers, workstations,
Macintoshes.
Functions: Provide user
interface, perform some /
most processing on an
application
Types: Servers,
workstations, or
midrange systems.
Functions: Shared
computation,
application
control,
distributed
databases
Host systems/
superservers
Types: mainframes
and midrange
systems.
Functions: Central
databases control
security, directory
management, heavyduty processing.
Figure 7.5: The functions of the computer systems in client/server networks.
Network Computing. Network computing or network-centric concept views networks as
the central computing resources of any computing environment. The growing reliance
on the computer hardware, software, and data resources of the Internet, intranets,
extranets, and other networks has emphasized that for many users, ‘the network is the
computer’ (figure 7.6).
User
interface
Network computer
and other clients
provide a browserbased user interface
for applet processing
System and
application
software
Application servers
for multi-user
operating systems,
Web server software,
and application
software applets
Database and
database
management
Database servers for
Internet/intranet
Web databases,
operational
databases, and
database
management
software
Figure 7.6 The functions of the computer systems in network computing
Peer-to-peer networks. This network is a civilization –altering event for the media
industry. Every consumer now is a producer, distributor, and marketer of intellectual
property and information content (a ’human node’) with vast new powers. In a P2P
network it creates a computing environment where end users computers connect,
communicate, and collaborate directly with each other via Internet or other
telecommunications network links.
The emergence of peer-to-peer (P2P) networking technologies and applications is being
hailed as a development that will revolutionize e-business and e-commerce and the
Internet itself. Peer-to-peer network is a powerful telecommunications networking tool
for many business applications (figure 7.7).
Figure 7.7 Peer-to-peer networks
Napster Peer-to-Peer Networks Architecture
The program "Napster" came into being in January 1999 when Shawn Fanning, a
freshman at Northeastern University, wrote an application to allow music sharing
between people in his dormitory. Napster Inc. was founded in May of that year and
scaled up to massive 21 million users. It took only until December 1999 before the
record industry of America sued Napster for copyright infringements and currently,
although Napster is still in operation, it has only a tiny fraction of its once huge user
base.
Napster is based on a client - server architecture. The role of the server is to hold a
searchable index that contains entries of mp3s that all the currently connected clients
contain. The server is actually multiple very hi-spec machines load balancing the
requests from clients. This makes scaling the service simply a matter of adding machines
into the server pool and ensures redundancy in the fact that servers can fail and be
replaced without significant disruption to the service they are providing. Redundancy
needs to be implemented for the connection between client and server as well so the
servers are placed on multiple connections to different large ISPs.
The clients have the functionality of being able to index and associate meta-data with
shared mp3s on their own machine. This information is then sent to the Napster servers
when connecting. At this point the client may search all clients connected on Napster by
sending search queries to the Napster server. The server will search its internal indexes
of currently shared files and return results to match. The results contain the meta-data
about the file, the location of the file and speed of the clients that are sharing the files. If
the client wishes to download one of the files contained in the search results then it
connects directly to the other client sharing the file and begins the download. The file
itself never passes through or is stored on the Napster server. This is the peer-to-peer
aspect of the protocol.
In the Napster architecture, P2P file-sharing software connects the user’s PC to a
central server that contains a directory of all of the other users (peers) in the network.
When users request a file, the software searchers the directory for any other users who
have that file and are online at the moment. It then sends you a list of the users’ names
that are active links to all users.
Figure 7.8 Napster Peer-to-peer network architecture
Gnutella Peer-to-Peer Networks Architecture
On the 14th of March 2000 Nullsoft, a subsidiary of America Online, released a file
sharing application called GNUtella that allowed file swapping without the need of a
central indexing server and therefore no central point of failure, and no central point to
sue for copyright infringements. On April 10th America Online declared GNUtella to be a
rogue project and terminated it, but not before the program had been downloaded and
replicated by thousands of users around the net. Over the next few weeks the protocol
was reverse engineered and GNUtella clones began to appear.
The Gnutella architecture is a pure peer-to-peer network since there is no central
directory or server. First, the file-sharing software in Gnutella-style P2P network
connects your PC with one of the online users in the network. Then an active link to
your user name is transmitted from peer to peer to all the online users in the network
that the first user (an all other online users) encountered in previous sessions. In this
way, active links to more and more peers spread throughout the network the more it is
used.
GNUtella's architecture is completely decentralised and distributed, meaning that there
are no central servers and that all computations and interactions happen between
clients. All connections on the network are equal. When a client wishes to connect to
the network they run through a list of nodes that are most likely to be up or take a list
from a website and then connect to how ever many nodes they want. This produces a
random unstructured network topology.
Routing in the network is accomplished through broadcasting. When a search
request arrives into a client that client searches itself for the file and broadcasts the
request to all its other connections. Broadcasts are cut off by a time to live that specifies
how many hops they may cover before clients should drop them rather than broadcast
them. There is a small degree of anonymity provided on GNUtella networks by this
packet routing technique. Any client that receives a packet doesn't know if the client it
has received the packet from is the original sender or just another link in the chain. This
is somewhat undermined however by the fact that nearly all packets on the network
start with a TTL (time to live) of 7 and therefore if you receive a packet with a TTL of 7
you can be nearly certain that the packet has originated from your immediate upstream
neighbour. GNUtella allows the functionality of being able to search for files. All other
operations such as uploads and downloads occur outside of the network and will be
explained later.
Figure 7.9 Gnutella Peer-to-Peer Networks Architecture
7.4 Network Topologies
Topology describes the appearance or layout of a network and how data flows through
the network. A network is a computer system that uses communication equipment to
connect computers. They can be connected in different ways. The physical layout of a
network is called a topology. There are three common topologies: star, ring, and bus
networks. In a network topology, a component is called a node, which is usually a
computer on a network. (The term node is also use to refer to any device connected to a
network, including the server, computers, and peripheral device such as printers.)

Star network. A star network has a hub computer that is responsible for
managing the network. A star network features a central connection point called
a hub that may be a hub, switch or router (figure 7.10). All devices are connected
to a central point called a hub. These hubs collect and distribute the flow of data
within the network. Signals from the sending computer go to the hub and are
then transmitted to all computers on the network. Large networks can feature
several hubs. Devices typically connect to the hub with Unshielded Twisted Pair
(UTP) Ethernet. A star network is easy to troubleshoot because all information
goes through the hub, making it easier to isolate problems. Compared to the bus
topology, a star network generally requires more cable, but a failure in any star
network cable will only take down one computer’s network access and not the
entire LAN.
The main advantages of a star network are:
a) All messages are routed through the central computer, which act as a traffic
cop to prevent collisions.
b) Any connection failure between a node and the hub will not affect the
overall system.
The main disadvantage of a star network is:
a) if the hub computer fails the network fails.
Figure 7.10 Star Network

Ring network. A ring network links all nodes together in a circular chain. Data
message travel in only one direction around the ring (figure 7.11). Any data that
passes by is examined by the node to see if it is the addressee; it not, the data is
passed on to the next node in the ring. In a ring network, every device has
exactly two neighbors for communication purposes. All messages travel through
a ring in the same direction (either “clockwise” or “counterclockwise”). A failure
in any cable or device breaks the loop and can take down the entire network.
Ring topologies are found in some office buildings or school campuses.
The main advantage of a ring network is:
a) Since data travels in only one direction, there is no danger of data collision.
The main disadvantage of a ring network is:
a) is one node fails, the entire network fails.
Figure 7.11 Ring Network

Bus network. A bus network has a single line to which all the network nodes are
attached (figure 7.12). Computers on the network transmit data in the hope that
it will not collide with data transmitted by other nodes; if this happens, the
sending node simply tries again. Nodes can be attached to or detached from the
network without affecting the network. Furthermore, if one node fails, it does
not affect the rest of the network.
Figure 7.12 BUS Network
Bus networks use a common backbone to connect all devices. The backbone is a high
capacity communications medium that joins networks and central network devices
on the same floor in a building. A single cable, the backbone functions as a shared
communication medium, that device attach or tap into with an interface connector.
A device wanting to communicate with another device on the network sends a
broadcast message onto the wire that all other devices see, but only the intended
recipient actually accepts and processes the message.
The main advantages of a bus network are:

Easier to locate problem workstations

depending on the backbone can provide very fast networks
The main disadvantage of bus networks are:

issues with security as data is broadcasted across the network

Single point of failure - if hub or backbone goes down
7.5 Keeping Your Home Computer Safe
Protect hardware. There is an active market for stolen personal computers and their
internal components. As a remedy, all computer hardware and computers’ internal
components should be locked. In addition, personal computers users need to be
concerned about the computer’s environment. Personal computers are designed to
withstand the wear and tear of the office environment. Most manufactures discourage
eating and smoking near computers and recommend some specific cleaning techniques,
such as vacuuming the keyboard.
Back up File. You should back up your files at regular basis. Some people simply make
another copy of their hard disk files on diskettes. A better way to back up your files on a
tape because it is faster and safer. You can also use software that will automatically
back up all your files at certain time of the day.
7.6 Computer Threats: Hackers
Hackers are enthusiastic, largely self-taught computer user who gains access to
computer systems illegally, usually from a personal computer. The term hackers used to
mean a person with significant computer expertise, but the term has taken on more
sinister meaning with the advent of computer miscreants. Hackers ply their craft for a
variety of reason but most often to show off for their peers or to harass people they do
not like. A favorite tricks, for example, is turn a rival’s telephone into a pay phone, so
that when his or her parent try to dial a number an operator would interrupt to say,
“please deposit 25 cent.” A hacker may have more sinister motives, such as getting
computer services without paying for them or getting information to sell.
You will probably not be surprised to learn that hackers have invaded websites. These
vandals show up with what amounts to a digital spray can, defacing sites with taunting
boasts, graffiti, and their own private jokes. Although the victims feel violated, the
perpetrator views their activities as mere pranks.
Hackers and Other Miscreants
Hacking has long been thought the domain of teenagers with time on their hands. The
pattern is changing, however. A recent government survey showed that the computer
system of over half of the largest U.S. corporations had been invaded, but not by
teenagers. Most intruders were competitors stealing proprietary information. For
example, suppose a biomedical company discovers just one little research secret in a
competitor’s computer files; the snooping company may then be the first to market
with a drug that the invaded company has been working on for years. Even more
astounding, federal investigators told a U.S. Senate hearing that the abilities of other
nations, which, in a worst-case scenario, could seriously degrade the military’s ability to
deploy and sustain military forces.
Hackers ply their craft by surprisingly low-tech means. Using what is called social
engineering, a tongue-in-check term for con artist actions, hackers simply persuade
unsuspecting people to give away their passwords over the phone. Recognizing the
problem, employers are educating their employees to be alert to such scams.
Hackers are only a small fraction of the security problem. The most serious losses are
caused by electronic pickpockets who are usually a good deal older and not so harmless.
Consider these examples:

A brokerage clerk sat at his terminal in Denver and with a few taps of the keys
transformed 1700 shares of his own stock, worth $1.50 per share, to the same
number of shares in another company worth ten times that much.

A Seattle bank employee used her electronic fund transfer code to move certain
bank funds to an account held by her boyfriend as a “joke”; both the money and
the boyfriend disappeared.

A keyboard operator in Oakland, California, changed some delivery address to
divert several thousand dollars’ worth of department store goods into the hands
of accomplices.

A tickets clerk at the Arizona Veteran’s Memorial Coliseum issued full-price
basketball tickets for admission and pocketed the difference.
These stories point out that computer crime is not always the flashy, front-page news
about geniuses getting away with millions of dollars. These people are ordinary
employees in ordinary business-committing computer crimes.
The problems of computer crime have been aggravated in recent years access to
computer. More employees now have access to computer at work, he or she also gains
knowledge that-potentially-could be used to harm the company.
The Changing Face of Computer Crime
Computer crime once fell into a few simple categories, such as theft of software or
destruction of data. The dramatically increased access to networks has changed the
focus to damage that can be done by unscrupulous people with online access. The most
frequently reported computer crimes fall into these categories:

Credit card fraud. Costumer numbers are floating all over public and private
networks, in varying states of protection. Some are captured and used
fraudulently.

Data communication fraud. This category covers a board spectrum, including
piggybacking on someone else’s network, the use of an office network for
personal purposes, and computer-directed diversion of funds.

Unauthorized access to computer files. This general snooping category covers
everything from accessing confidential employee records to the theft of trade
secret and product pricing structure.

Unlawful copying of copyrighted software. Whether the casual sharing of
copyrighted software among friends or assembly line copying by organized
crime, unlawful copying incurs major losses for software vendors.
Discovery and Prosecution
Prosecution the computer criminal is difficult for several reasons. To begin with,
discovery is often difficult. Many times the criminal simply goes undetected. In addition,
crimes that are detected are-an estimated 85 percent of the time-never reported to the
authorities. By law, banks have to make a report when their computer systems have
been compromised but other businesses do not. Often they choose not to report such
crimes because they are worried about their reputations and credibility in the
community.
Most computer crimes are discovered by accident. For example, a bank employee
changed a program to add 10cent to every customer service charge under $10 and $1 to
every charge over $10. He then placed this overage into the last account, a bank
account he opened himself in the name of Zzwicke. The system worked fairly well,
generating several hundred dollars each month, until the bank initiated a new
marketing campaign in which it singled out for special honors the very first depositorand the very last. In another instance some employees of city welfare department
created a fictitious work force, complete with social security numbers, and programmed
the computer to issue paychecks, which the employees would then intercept and cash.
They were discovered when a police officer investigated and illegally parked overdue
rental car and found the fraudulent checks inside.
Even if a computer crime is detected, prosecution is by no means assured. There are a
number of reasons for this. First, some law enforcement agencies do not fully
understand the complexities of computer-related fraud. Second, few attorneys are
qualified to handle computer crimes cases. Third, judges and juries are not always
educated about computers and may not understand the nature of violation or the
seriousness of the crime.
In short, the chances of having a computer crime go undetected are, unfortunately,
good. And the chances that, if detected, there will be no ramifications are also good: a
computer criminal may not go to jail, may not be found guilty if prosecuted.
But this situation is changing. Since USA Congress passed the Computer Fraud and
Abuse Act in 1986, there has been growing awareness of computer crime on the
national level. This law is supplemented by state statues; most states have passed some
form of computer crimes law. Computer criminals that are successfully prosecuted are
subject to fines, jail time, and confiscation of their computer equipment.
7.7 Computer Safeguards: Firewalls
An important method for control and security on the Internet and other networks is the
use of firewall computers and security software. Firewall protects computer networks
from intrusion by screening all network traffic and serving as a safe transfer point for
access to and from other network.
A network firewall can be a communication processor, typically a router or a dedicated
server, along with firewall software. A firewall serves as a gatekeeper system that
protects a company’s intranets and other computer networks from intrusion by
providing a filter and safe transfer point for access to and from the Internet and other
networks. It screens all network traffic for proper passwords or other security codes,
and only allows authorized transmissions in and out of the network. Firewalls have
become an essential component of organizations connecting to the Internet, because of
its vulnerability and lack of security.
Firewalls can deter, but not completely prevent, unauthorized access (hacking) into
computer networks. In some cases, a firewall may allow access only from trusted
locations on the Internet to particular computers inside the firewall. Or it may allow only
‘safe’ information to pass. For example, a firewall may permit users to read e-mail from
remote locations but not to run certain programs. In other cases, it is impossible to
distinguish safe use of a particular network service from unsafe and so all requests must
be blocked. The firewall may then provide substitutes for some network services (such
as e-mail or file transfer) that perform most of the same functions but are not so
vulnerable to penetration.
7.8 Securing Networks
The goal of security of security management is the accuracy, integrity, and the safety of
all system processes and resources. Effective security management can minimize errors,
fraud and losses in the internetworked computer-based systems that interconnect
today’s e-business enterprise.
Networks (whether connected to Internet of not) pose unique security and privacy
problems. Organizations must be concerned about unauthorized people intercepting
data in transmit, whether hackers or thieves or industrial spies. Networks can be
secured by the following:

Firewall. One fundamental approach to network security is to dedicate one
computer called a firewall, whose sole purpose is to talk to the outside world A
firewall will provide an organization with greatly increased security because only
one network computer is accessible to people outside the network, and that one
computer accepts only appropriate access.

Encryption. Data being sent over communication lines may be protected by
scrambling the messages that is, putting the messages in code that can be
broken only by the person receiving the message. The process of scrambling
messages is called encryption. Encryption protects data by scrambling data or
converting it, prior to transmission, to a secret code that masks the meaning of
the data to unauthorized recipients.
The American National Standard Institute (ANSI) has endorsed a process called
Data Encryption Standard (DES), a standardized public key by which senders and
receivers can scramble and unscramble their messages. Although DES code is
well known, companies still use it because the method makes it quite expensive
to intercept coded messages. Thus, interlopers are forced to use other methods
of gathering data – methods that carry greater risk of detection. Encryption
software is available for personal computers. A typical package for example
offers a variety of security features file encryption, keyboard lock, and password
protection.
Organizations are advised to have a disaster recovery plan for its computer system. A
disaster recovery plan is a method of restoring computer processing operations and
data files if operations are halted or files are damaged by major destructions. There are
various approaches. Some organizations revert temporarily to manual services, but life
without the computer can be difficult indeed. Others arrange to buy time at a service
bureau, but this is inconvenient for companies in remote or rural area. If a single act,
such as fire, destroys your computing facility, it is possible that a mutual aid pact will
help the organization to continue running its business. In such a plan, two or more
companies agree to lend each other computing power if one of them has a problem.
Other organizations sometimes form a consortium, a joint venture to support a
complete computer facility. Such facility is completely available and routinely tested but
used only in the event of disaster.
7.9 Computer Threats: Computer Viruses
Worms and viruses are rather unpleasant terms that have entered the jargon of the
computer industry to describe some of the insidious ways that computer system can be
invaded.
A worm is a program that transfers itself from computer to computer over a network
and plants itself as a separate file on the target computer’s disk. One newsworthy
worm, originated by Robert Morris when he was a student at Cornell University,
traveled the length and breadth of the land through an electronic mail network, shutting
down thousands of computer. The worm was injected into the network and multiplied
uncontrollably, clogging the memories of infected computers until they could no longer
function.
A virus, as its name suggests, is contagious. That is a virus, set of illicit instruction,
passes itself on to other programs or document with which it comes in contact. In its
most basic form, a virus is digital equivalent of vandalism. It can change or delete files,
display words or obscene massage, or produce bizarre screen effects. In its most
vindictive form, a virus can slowly sabotage a computer system and remain undetected
for months, contaminating data or, in this case of the famous Michelanglo virus, wiping
out your entire hard drive. A virus may be dealt with by means of a vaccine, or antivirus,
a computer program that stop the spread of and often eradicates the virus. However, a
retrovirus has the ability to fight back and may even delete antivirus software.
Viruses seem to show up when least expected. In one instance call came to a company’s
information center at about 5:00 p.m. The caller’s computer making a strange noise.
With the expectation of an occasional beep, computer performing routine business
chores do not usually make noises. Soon employees were calling from all over the
company, all with “noisy” computers. One caller said that it might be a tune coming
from the computer’s small internal speaker. Finally, one caller recognized a tinny
rendition of “Yankee Doodle” confirmation that an old virus had struck once again. The
Yankee Doodle virus, once attached to a system, is scheduled to go off at 5:00 p.m.
every eight days. Viruses, once considered merely a nuisance, are costing American
business over $2 billion a year. Unfortunately, viruses are easily transmitted.
You may wonder who produces viruses. At one point, the mischief makers were merely
teenagers with too much time on their on their hands. Now, virus makers are older and
actually trade notes and tips on the Internet. They do what they do, psychologist say,
mostly to impress their friends. Experts have estimated that there are hundreds of virus
writers worldwide. However, although there are thousands of unknown viruses, most of
the damage is cause by only a dozen or so.
Transmitting a Virus. A virus can be transmitted easily via Internet. Each time a user
runs the virus program, it will be loaded into the memory of the computer that the users
used.. The virus stays in memory, infecting any other program loaded until the
computer is turned off again. The virus not now has spread to other programs, and the
process can be repeated again and again. In fact, each newly infecting program becomes
a virus carrier. Although many virus are transmitted just way via networks, the most
common method is by passing diskettes from computer to computer.
Here is another typical scenario. An office worker puts a copy of a report on a diskette
and slips it into her briefcase to take home. After shooing her children away from the
new game they are playing on the computer, she sits down to work on the report. She
does not know that a virus, borne by the kids’ new software, has infected the diskette.
When she takes the disk back down to work, the virus is transmitted from her computer
to the entire office network.
The most insidious viruses attach to the operating system. One virus, called Cascade,
causes random text letter to “drop” to a pike at the bottom to the screen. Viruses
attached to the operating system itself have greater potential for mischief.
A relative newcomer to the virus scene is the macro virus, which uses a program’s own
macro programming language to distribute itself. Unlike previous viruses, a macro virus
does not infect a program; it infects a document. When you open the document that
has the virus, any other document opened in same session may get virus too.
Damage from Viruses.
Most viruses remain dormant until triggered by some activity.
For example, a virus called Jerusalem B activates itself every Friday the 13 th and
proceeds to erase any file you may try to load from your disk. Another virus include
instructions to add 1 to a counter each time the virus is copied to another disk. When
the counter reaches 4, the virus erases all data files. All the other three copied disks
have also been infected. The Concept virus, a relatively benign macro virus, refuses to
let users to save their documents after they have made changes., saying the file is ‘read
only’. The Nuclear macro virus, among other things destroys vital operating system files
on any April 5th.
Prevention. Although viruses are most commonly passed via diskettes, viruses can
propagate by other means, such as local area network, electronic mail, and the Internet.
Furthermore, viruses are rampant on some college campuses. Use these commonsense
approaches to new files:

Use virus-scanning software to check any file or document before loading it onto
your hard disk.

Never install a program unless the diskettes come in a sealed package.

Be especially wary of software that arrives unexpectedly from companies with
whom you have not done business
Although there have been isolated instances of viruses in commercial software, viruses
tend to show up on free software or software acquired from friends or the Internet.
Antivirus software can be installed to scan the hard disk every time the computer is
booted or at regular scheduled intervals.
Summary
A network is an interconnected system of computers, terminals, and communications
channels and devices. Networking includes local area networks (LAN) which are
designed to share data and resources among several individual computer users in an
office or building. Many different types of networks serve as the telecommunications
infrastructure for the Internet, intranets and extranets
A protocol is a standard set of rules and procedures for the control of communications
in a network. Part of the goal of communication network architecture is to create more
standardization and compatibility among communication protocols.
An important method for control and security on the Internet and other networks is the
use of firewall computers and security software.
Reference:
James O’Brien, Introduction to Information Systems, McGraw-Hill, 2003.
H.L. Capron, Computers Tools for an Information Age, Addision Wesley, 1997.
Loudon and Loudon, Essentials of Management Information Systems, Prentice Hall,
2001.
www.csm.ornl.gov/~dunigan/vpn.html
True / False Questions
No.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Questions
Answer
The basic components for networking consists of
communication system used to transmit the messages are
(1) a sending device (2) a communication channel, and (3) a
receiving device.
Michelanglo is a protocol standard set of rules and
procedures for the control of communications in a network.
There are eight layers of the OSI communications network
architecture, and the seven layers of the Internet’s TCP/IP
protocol suite.
The goal of network architectures is to promote an open,
simple, flexible, and efficient telecommunications
environment.
In a client/server networks, end-user PC or NC workstations
are the clients. They are interconnected by local area
networks and share application processing with network
servers.
The goal of security of security management is the accuracy,
integrity, and the safety of all system processes and
resources.
In a bus network, all messages are routed through the
central computer.
A firewall serves as a gatekeeper system that protects a
company’s intranets and other computer networks from
intrusion by providing a filter and safe transfer point for
access to and from the Internet and other networks.
Installing antivirus software to scan the hard disk every time
the computer is booted or at regular scheduled intervals is
an example to protect your computer.
Many times the computer criminal can be easily detected
True
False
False
True
True
True
False
True
True
False
Presentation Slides
Slide 1
Topic 7
Networking and Security
Slide 2
Learning Outcome
Learning Outcome
At the end of the lesson, the students will be able to:







Define what is computer network system.
Identify the basic components of computer networking
system.
Understand the different type of network architectures.
Discuss the importance of protocols.
Discuss the different type of network topologies.
Aware of the potential threat to computer and its network
Aware of computer viruses and how they spread.
Slide 3
List of Topics

Networking Fundamentals

Network Architectures and Protocols

Type of Communications Networks

Network Topologies

Keeping Your Home Computer Safe

Computer Threats: Hackers

Securing Networks

Computer Threats: Computer Viruses
Slide 4
List of terminology
Computer system
network
Communications systems connecting two or more computers
and their peripherals devices to exchange information and share
resources.
Terminals
Any input/output device that uses telecommunication networks
to transmit or receive data is a terminal, including telephones
and the various computer terminals.
Telecommunications Supports data transmission and reception between terminals and
processors
computers.
Telecommunications Over which data are transmitted and received.
channels
Telecommunications Consists of programs that control telecommunications activities
control software
and manage the functions of telecommunications networks. E
Network
Architectures
Describes how networks are configured and how the resources
are shared.
Protocols
A standard set of rules and procedures for the control of
communications in a network.
OSI Model
The International Standards Organization (ISO) has developed a
seven-layer Open Systems Interconnection (OSI) model to serve
as a standard model for network architectures.
TCP/IP
The Internet’s protocols suite.
Wide area network
(WAN)
Local Area Networks
(LAN)
Telecommunications networks covering a large geographic area.
Virtual private
networks
A secure network that uses the Internet as its main backbone
Connects computers and other information processing devices
within a limited physical area, such as an office,
network but relies on the fire walls and other security features of
its Internet and intranet connections and those of participating
organizations
Client/server
networks
Network in which one powerful computer coordinates and
supplies to all other nodes on the network. Server nodes
coordinate and supply specialized services, and client nodes
request the services.
Peer-to-peer
networks
Network in which nodes can act as both servers and clients. For
example, one microcomputer can obtain files located on another
microcomputer and also can provide files to other
microcomputers.
Network Topology
Describes the appearance or layout of a network and how data
flows through the network.
Star network
Network of computers or peripherals devices linked to a central
computer through which all communication pass.
Ring network
Network of computers in which each device is connected to two
other devices, forming a ring.
Bus network
Network in which all communications travel along a common
connecting cable called a bus. Also known as Ethernet.
Firewall
Protects computer networks from intrusion by screening all
network traffic and serving as a safe transfer point for access to
and from other network.
Slide 5
Computer Network



Uses communication equipment to connect two or
more computers and their resources.
An interconnected system of computers, terminals, and
communications channels and devices.
Includes local area networks (LAN) which are designed
to share data and resources among several individual
computer users in an office or building.
Slide 6
Basic components for networking
 A communication network is any arrangement where a
sender transmits a message to a receiver over a
channel consisting of some type of medium
 Consists of communication system used to transmit the
messages :
 a sending device
 a communication channel
 a receiving device.
Slide 7
Telecommunication
Processors
PCs, NCs and
other
terminals
Telecommunications
channels
Telecommunication
Processors
Computers
Figure 7.1: The five basic components for telecommunications network
Slide 8
Network Components
 Terminals such as networked personal computers, network
computers, or information appliances.
 Telecommunications processors support data transmission and
reception between terminals and computers.
 Telecommunications channels over which data are transmitted
and received.
 Computers are interconnected by telecommunications
networks so that they can carry out their information
processing tasks.
 Telecommunications control software consists of programs
that control telecommunications activities and manage the
functions of telecommunications networks.
Slide 9
Network Architecture

The goal of network architectures is to promote an open,
simple, flexible, and efficient telecommunications
environment.

Accomplished by the use of standard protocols, standard
communications hardware and software interfaces, and the
design of a standard multilevel interface between end users
and computer systems.
Slide 10

.
Protocols
A standard set of rules and procedures for the control of
communications in a network.

Part of the goal of communication network architecture is to
create more standardization and compatibility among
communication protocols.

One example of a protocol is;
 A standard for the physical characteristics of the cables and
connectors between terminals, computers, modems, and
communication lines.
 Protocols that establish the communication control
information needed for handshaking which is the process or
exchanging predetermined signals and characters to
establish a telecommunications session between terminals
and computers.
 Protocols deal with control of data transmission reception in
a network, switching techniques, internetwork connections,
Slide 11



.
The OSI Model
Developed by the International Standards
Organization (ISO)
Has a seven-layer Open Systems Interconnection
(OSI) model to serve as a standard model for
network architectures.
Dividing data communications functions into seven
distinct layers promotes the development of
modular network architectures, which assists the
development, operation, and maintenance of
complex telecommunications networks.
Slide 12
TCP/IP
Application for
Process Layer
Application
Layer
Provides communications services for
end user applications
Presentation
Layer
Provides appropriate data
transmission formats and codes
Session
Layer
Support the accomplishment of
telecommunications sessions
Host-to-Host
Transport Layer
Transport
Layer
Supports the organization and
transfer of data between nodes in
the network
Internet Protocol (IP)
Network
Layer
Provides appropriate routing by
establishing connections among
network links
Network Interface
Data Link
Layer
Supports error-free organization
and transmission of data in the
network
Physical Layer
Physical
Layer
Provides physical transmission of
data on the telecommunications
media in the network
Figure 7.2: The seven layers of the OSI communications network architecture,
and the five layers of the Internet’s TCP/IP protocol suite
Slide 13

The Internet’s TCP/IP
Internet’s protocols suite is called Transmission Control
Protocol/Internet Protocol and is known as TCP/IP.

A system of telecommunications protocols that has become
so widely used that it is equivalent to a network architecture.

TCP/IP consists of five layers of protocols that can be related
to the seven layers of the OSI architecture.

TCP/IP is used by the Internet and by all intranets and
extranets.
Slide 14
Type of Communications Networks

Many different types of networks serve as the
telecommunications infrastructure:
 wide area networks
 local area networks
 client/server networks
 network computing networks
 peer-to-peer networks.
Slide 15



Wide Area Network (WAN)
Telecommunications networks covering a large geographic area.
Networks that cover a large city or metropolitan area
(metropolitan area networks) can also be included in this
category.
WANs are used by many multinational companies to transmit
and receive information among their employees, customers,
suppliers, and other organizations across cities, regions,
countries and the world.
Slide 16
Wide Area Network
Slide 17
Local Area Networks (LAN)





Connects computers and other information processing devices
within a limited physical area, such as an office, classroom,
building, manufacturing plant, or other work site.
LANs have become commonplace in many organizations for
providing telecommunications network capabilities that link end
users in offices, departments and other workgroups.
Uses a variety of telecommunications media to interconnect
microcomputer workstations and computer peripherals. .
Each PC usually has a circuit board called a network interface
card.
Most LANs use a more powerful microcomputer having a large
hard disk capacity, called a file server or network server, that
contains a network operating system program that controls
telecommunications and the use and sharing of network
resources.
Slide 18
Local Area Network
Slide 19
Virtual Private Networks




Organizations use Virtual Private Networks (VPNs) to establish secure
intranets and extranets.
A virtual private networks is a secure network that uses the Internet as
its main backbone network but relies on the fire walls and other
security features of its Internet and intranet connections and those of
participating organizations.
VPNs would enable a company to use the Internet to establish secure
intranets between its distant branch offices and the manufacturing
plants, and secure extranets between itself and its customers and
suppliers.
The basic idea is to provide an encrypted IP tunnel through the Internet
that permits distributed sites to communicate securely. The encrypted
tunnel provides a secure path for network applications and requires no
changes to the application.
Slide 20
Virtual Private Networks
Slide 21
Client/Server Networks



In a client/server networks, end-user PC or NC workstations are the
clients.
They are interconnected by local area networks and share application
processing with network servers, which also manage the networks.
Local area networks are also interconnected to other LANs and WANs
of client workstations and servers.
Slide 22
Client/Server Networks
Slide 23
Functions of the Computer Systems in Client/Server Networks
Servers
Client system
Types: PCs, Network
computers,
workstations,
Macintoshes.
Functions: Provide
user interface,
perform some / most
processing on an
application
Types: Servers,
workstations, or
midrange systems.
Functions: Shared
computation,
application control,
distributed databases
Host systems/
superservers
Types: mainframes
and midrange
systems.
Functions: Central
databases control
security, directory
management,
heavy-duty
processing.
Slide 24



Peer-to-Peer Networks
A computing environment where end users computers connect,
communicate, and collaborate directly with each other via
Internet or other telecommunications network links.
The emergence of peer-to-peer (P2P) networking technologies
and applications is being hailed as a development that will
revolutionize e-business and e-commerce and the Internet
itself.
Peer-to-peer network is a powerful telecommunications
networking tool for many business applications
Slide 25
Peer-to-peer networks
Slide 26
Napster Peer-to-Peer Networks Architecture





Napster is based on a client - server architecture.
The role of the server is to hold a searchable index that
contains entries that all the currently connected clients
contain.
The server is actually multiple very hi-spec machines load
balancing the requests from clients. This makes scaling the
service simply a matter of adding machines into the server
pool and ensures redundancy in the fact that servers can fail
and be replaced without significant disruption to the service
they are providing.
In the Napster architecture, P2P file-sharing software
connects the user’s PC to a central server that contains a
directory of all of the other users (peers) in the network.
When users request a file, the software searchers the
directory for any other users who have that file and are
online at the moment. It then sends you a list of the users’
names that are active links to all users.
Slide 27
Napster Peer-to-peer Network Architecture
Slide 28
Gnutella Peer-to-Peer Networks Architecture





GNUtella that allowed file swapping without the need of a central
indexing server and therefore no central point of failure, and no
central point to sue for copyright infringements.
The Gnutella architecture is a pure peer-to-peer network since there is
no central directory or server.
First, the file-sharing software in Gnutella-style P2P network connects
your PC with one of the online users in the network.
Then an active link to your user name is transmitted from peer to peer
to all the online users in the network that the first user (an all other
online users) encountered in previous sessions.
In this way, active links to more and more peers spread throughout
the network the more it is used.
Slide 29
Gnutella Peer-to-Peer Networks Architecture
Slide 30
Network Topologies




Topology describes the appearance or layout of a network and how data
flows through the network.
A network is a computer system that uses communication equipment to
connect computers. They can be connected in different ways.
The physical layout of a network is called a topology.
There are three common topologies: star, ring, and bus networks. In a
network topology, a component is called a node, which is usually a
computer on a network. (The term node is also use to refer to any device
connected to a network, including the server, computers, and peripheral
device such as printers.)
Slide 31
Star Network





A star network has a hub computer that is responsible for managing
the network.
A star network features a central connection point called a hub that
may be a hub, switch or router.
All devices are connected to a central point called a hub. These
hubs collect and distribute the flow of data within the network.
Signals from the sending computer go to the hub and are then
transmitted to all computers on the network. Large networks can
feature several hubs.
A star network is easy to troubleshoot because all information goes
through the hub, making it easier to isolate problems.
Slide 32
Advantages and Disadvantages of Star Network
The main advantages of a star network are:
 All messages are routed through the central computer, which act
as a traffic cop to prevent collisions.
 Any connection failure between a node and the hub will not affect
the overall system.
The main disadvantage of a star network is:
 if the hub computer fails the network fails.
 Requires more cabling
Slide 33
Star Network
Slide 34
Ring Network





. 
A ring network links all nodes together in a circular chain.
Data message travel in only one direction around the ring
Any data that passes by is examined by the node to see if it is the
addressee; it not, the data is passed on to the next node in the
ring. In a ring network, every device has exactly two neighbors for
communication purposes.
All messages travel through a ring in the same direction (either
“clockwise” or “counterclockwise
Ring topologies are found in some office buildings or school
campuses.
Slide 35
Advantages and Disadvantages of Ring Network
The main advantage of a ring network is:
 Since data travels in only one direction, there is no
danger of data collision.
The main disadvantage of a ring network is:
 is one node fails, the entire network fails.
 A failure in any cable or device breaks the loop and
can take down the entire network.
Slide 36
Ring Network
Slide 37
Bus Network







A bus network has a single line to which all the network nodes are
attached.
Computers on the network transmit data in the hope that it will not collide
with data transmitted by other nodes; if this happens, the sending node
simply tries again.
Nodes can be attached to or detached from the network without affecting
the network.
Furthermore, if one node fails, it does not affect the rest of the network.
Bus networks use a common backbone to connect all devices.
A single cable, the backbone functions as a shared communication
medium, that device attach or tap into with an interface connector.
A device wanting to communicate with another device on the network
sends a broadcast message onto the wire that all other devices see, but
only the intended recipient actually accepts and processes the message.
Slide 38
BUS Network
Slide 39
Advantages and Disadvantages of Bus Network
The main advantages of a bus network are:


Easier to locate problem workstations
depending on the backbone can provide very fast networks
The main disadvantage of bus networks are:


issues with security as data is broadcasted across the network
Single point of failure - if hub or backbone goes down
Slide 40
Keeping Your Home Computer Safe
 Protect hardware
 From theft
 From dust

Back up File.
 Back up your files at regular basis.
 Make copies of their hard disk files on diskettes.
 Computer Threats
 Hackers
 Virus
Slide 41
The Changing Face of Computer Crime

Computer crime once fell into a few simple categories, such as theft of
software or destruction of data.
 E.g. of computer crimes:
 Credit card fraud. Costumer numbers are floating all over public and
private networks, in varying states of protection. Some are captured and
used fraudulently.
 Data communication fraud. This category covers a board spectrum,
including piggybacking on someone else’s network, the use of an office
network for personal purposes, and computer-directed diversion of
funds.
 Unauthorized access to computer files. This general snooping category
covers everything from accessing confidential employee records to the
theft of trade secret and product pricing structure.
 Unlawful copying of copyrighted software. Whether the casual sharing
of copyrighted software among friends or assembly line copying by
organized crime, unlawful copying incurs major losses for software
vendors.
Slide 42
Discovery and Prosecution



Discovery of computer crime is often difficult. Many times the criminal
simply goes undetected
Crimes that are detected are-an estimated 85 percent of the timenever reported to the authorities. Reporting such crimes are not done
because companies are worried about their reputations and credibility
in the community.
Since USA Congress passed the Computer Fraud and Abuse Act in
1986, there has been growing awareness of computer crime on the
national level.
Slide 43
Computer Safeguards: Firewalls





A network firewall can be a communication processor, typically a
router or a dedicated server, along with firewall software.
A firewall serves as a gatekeeper system that protects a company’s
intranets and other computer networks from intrusion by providing a
filter and safe transfer point for access to and from the Internet and
other networks.
It screens all network traffic for proper passwords or other security
codes, and only allows authorized transmissions in and out of the
network.
Firewalls have become an essential component of organizations
connecting to the Internet, because of its vulnerability and lack of
security.
Firewalls can deter, but not completely prevent, unauthorized access
(hacking) into computer networks.
Slide 44
Securing Networks

The goal of security of security management is the accuracy,
integrity, and the safety of all system processes and resources.
 Effective security management can minimize errors, fraud and
losses in the internetworked computer-based systems that
interconnect today’s e-business enterprise.
 Networks can be secured by the following:
 Firewall protects computer networks from intrusion by screening all
network traffic and serving as a safe transfer point for access to and
from other network.
 Encryption protects data by scrambling data or converting it, prior
to transmission, to a secret code that masks the meaning of the data
to unauthorized recipients.
 Disaster recovery plan for its computer system. A disaster recovery
plan is a method of restoring computer processing operations and
data files if operations are halted or files are damaged by major
destructions.
Slide 45
Computer Threats
 Computer Viruses
 Worm: a program that transfers itself from computer to computer
over a network and plants itself as a separate file on the target
computer’s disk.
 Virus: set of illicit instruction, passes itself on to other programs or
document with which it comes in contact.
 Retrovirus has the ability to fight back and may even delete
antivirus software.
Slide 46
Prevention
 Precaution and use common sense approach:
 Use virus-scanning software to check any file or document before
loading it onto your hard disk.
 Never install a program unless the diskettes come in a sealed package.
 Be especially wary of software that arrives unexpectedly from
companies with whom you have not done business
Activity A
Crossword Puzzle
Answers
Questions
Network Topology
Describes the appearance or layout of a network and how
data flows through the network.
Star network
Network of computers or peripherals devices linked to a
central computer through which all communication pass.
Ring network
Network of computers in which each device is connected to
two other devices, forming a ring.
Bus network
Also known as Ethernet.
Terminals
Any input/output device that uses telecommunication
networks to transmit or receive data is a terminal, including
telephones and the various computer terminals.
Architectures
Describes how networks are configured and how the
resources are shared.
OSI Model
A seven-layer Open Systems Interconnection (OSI) model to
serve as a standard model for network architectures.
TCP/IP
The Internet’s protocols suite.
Wide area network (WAN) Telecommunications networks covering a large geographic
area.
Local Area Networks
(LAN)
Connects computers and other information processing
Virtual private networks
A secure network that uses the Internet as its main
devices within a limited physical area, such as an office,
backbone network but relies on the fire walls and other
security features of its Internet and intranet connections
and those of participating organizations
Client/server networks
Network in which one powerful computer coordinates and
supplies to all other nodes on the network.
Peer-to-peer networks
Network in which nodes can act as both servers and clients.
Group Activity
Discuss the various steps to ensure the security of your computer system against
potential threat.
Answers:
a) Install antivirus software.
b) Install firewall.
c) Take extra precaution when downloading files.
d) Clean any computer parts affected by virus.
Exercise
Drag and fill in the blank spaces.
TCP/IP
Firewall
Protocols
Topology
Network Architectures
1.
Network
Client
Telecommunications processors
WAN
Communication channel
__________ supports data transmission and reception between terminals and
computers.
2.
The transmission medium that carries the message is referred to as the
__________.
3.
Two or more computers connected so that they can communicate with each
other and share information are called a __________.
4.
A device, connected to a network, that shares resources with other computers is
called a _________.
5.
Standard protocols used for Internet is _________.
6.
The arrangement of the computers in a network is called a _____.
7.
The rules for exchanging data between computers are called __________.
8.
__________ describes how networks are configured and how the resources are
shared.
9.
__________ protects an organization’s network from outside attack.
10.
Telecommunications networks covering a large geographic area.
Answer:
1- Telecommunications processors
2- Communication channel
3-Network
4- Client
5-TCP/IP
6-Topology
7-Protocols
8- Network Architectures
9-Firewall
10-WAN