NETWORKS AND THE EFFECTS OF USING THEMTHIEN HA

NETWORKS

• A network is a group of computer systems and other computing hardware devices that are linked together through communication channels to communication with each other and to share data

Examples: Banking Network Message Network Airline Network

NETWORKS DEVICESS

MODEMS

• Means “modulator demodulator”• Converts computer’s digital signal to analogue signal• Does the reverse process to enable the computer to process data• Used to allow computers to connect to networks• Dial-up modems transmission speed is 60 kilobits / second and Modern

broadband or ADSL (asymmetric digital subscriber line) transmission speed is 100 megabits / second • ADSL modems can allow tel. conversations and internet traffic to occur

HUBS

• Hardware devices that can have devices or computer connected to them• Used to connect devices to form a LAN• Main task is to take any data packet and broadcast to every

computer in the network

BRIDGE

• Device that connect two LANs that uses the same protocol• Connect different parts of a LAN so they function as a single

LAN• Tend to be used to interconnected LANs since sending every

data packet may cause network traffic• That’s why a router’s used to communicate with other

networks (internet)

ROUTER

• Enable data packets to be routed between the different networks• Has an internet cable plugged into it and several cables connected to devices on

the LAN• Broadband routers sit behind a firewall that protect the computers• Main function is to transmit internet and transmission protocols between 2

networks and allow private networks to be connected• Inspects data packets and sends to the appropriate switch by (internet protocol)

IP, and then delivered using MAC destination address• If MAC doesn’t match, passes to another switch till appropriate device’s found

DATA PACKETS

• Usually contains:• Form of header to identify the data packets• Sender’s IP address• Receiver’s IP address• How many data packets in the message• Identity number of each packet

• Information allows router to send packets across network to its destination

OTHER HARDWARE

• Gateway• A network point that acts an entrance to another network• Key point for data going to or from other networks• If a network node needs to communicate outside its network, gateway is needed

• Network interface card (NIC)• Needed to allow device to connect to network, contains the MAC address generated already

• Network cables• Has faster data transfer rates and can be more secure than wireless networks

INTERNET PROTOCOL (IP) AND MEDIA ACCESS CONTROL (MAC) ADDRESS• Each device on internet is given an address known as

internet protocol (IP) address• IP address gives the location of device on the internet

• MAC address identifies the device on the internet

• IP can be changed but MAC address remains

WI-FI

• A wire transmitter (WAP) receives information from a network via its connection• Converts received info into radio waves and then transmits them• A device receives radio waves via wireless adaptor that allows it

to download info from the data source• A Wi-Fi enabled device can access internet at any access point

(AP) or hot spot 100m away

BLUETOOTH

• Sends and receives radio waves in 79 different frequencies• Devices using Bluetooth detect and connect to each other• Spread-spectrum frequency hopping is when device changes channel if it’s used

to connect to other device• Bluetooth’s useful:

• When transferring data between 2 or more devices that are close• Speed of data is not critical• For low-bandwidth applications

• Creates a secure wireless personal area network (WPAN) based on key encryption

HOW TO SET UP AND CONFIGURE A SMALL NETWORK• When setting up and configuring a network, think about doing the following:

• Setting up an IP account if internet access is required• Setting up the system• Configuring all the hardware and software so they work together• If internet’s required, ensure that high-speed broadband exists• Putting all the common software onto a server and a network license is acquired• Setting up privileges so each user can only access their area• Setting up a network-manager-level of privilege do that they can monitor network

usage, change passwords

LOCAL AREA NETWORKS (LANS)

ADVANTAGES• Sharing of resources• Ease of communication

between users• Network administrator to

control and monitor all aspects of the network

DISADVANTAGES• Easier spread of viruses through the

network• Printer queues developing• Slower access to external network• Increased security risk when compared to

stand-alone computers• If mains server breaks down, network won’t

function

WIDE AREA NETWORKS (WANS)

• Used where computers or networks are situated far away from each other• WANs usually make up some public communications network• They can also use leased communication lines which is less

expensive and more secure

WIRELESS LANS (WLANS)SIMILAR TO LANS BUT WITHOUT WIRE OR CABLES

USES RADIO OR INFRARED SIGNALS INSTEAD

APS USE SPREAD SPECTRUM TECHNOLOGY OR INFRARED

AP RECEIVES AND TRANSMITS DATA BETWEEN WLAN AND WIRED NETWORK STRUCTURE

ADVANTAGES• All computers can access the same

services and resources• No cabling needed, increased flexibility• Adding new computers and devices is

easy

DISADVANTAGES• Security can be a big issue• Necessary to adopt complex data

encryption techniques• There may be problems of interference• Data transfer rate is slower than wired

LAN

Expensive to use if Wi-Fi hot spot’s unavailable Very portable; can be

used wherever there’s a mobile phone network signal

A person is likely to have a mobile phone with them

Easier to use while on the move than other devicesSignal less likely to be

stable or reliable as a wired system

Not all websites are mobile-friendly

Keyboards are very small; difficult to type messages or navigate web pages

Displays on mobile phones are smaller than other devices

MOBILE PHONES AND TABLETS

Has more power processors than other devices Has more stable and

reliable internet since it uses wire system

All web pages are accessible due to large screen size

Use of full sized keyboards and pointing devices

Require expensive ‘dongles’ to access phone networks

Parts are all separate and large size, they’re aren’t portable

DESKTOP COMPUTERS

Screen size is usually bigger than a mobile but smaller than desktop

More mobile than desktops but less portable than phones

Laptops require expensive ‘dongles’ to enter phone networks

Touchpads on laptops aren’t as easy as a mouse but easier than mobile phones

Processors in laptops are not as powerful as those in desktops

Keyboards on laptops aren’t as easy as desktop but easier than mobile phone’s

LAPTOPS

SHOULD THE INTERNET BE POLICED

• There were many arguments for the past years• Arguments in favor of some form of control:

• Prevent illegal material to be posted• Prevent people from discovering info that has serious consequences• Help prevent children and other vulnerable groups from being subjected to undesirable website• Help stop incorrect info being published on websites

• Arguments against some form of control:• Material published on webs is available from other sources• Very expensive to 'police’ all websites and users would have to pick up the bill• Difficult to enforce rules and regulations on a global scale• Can be argued that policing would go against freedom of info• Laws already exist to deal with those who post illegal material

INAPPROPRIATE SITES AND THE ACCURACY OF INFO• Aspects to consider when looking at the quality of

information found on internet:• Reliability of information• Undesirability of certain websites• Security issues

RELIABILITY OF INFORMATION

• Information on the internet is more likely to be up to date than books• Much easier to get info from websites• There’s a vast amount of info on the internet that’s easier to

locate• Info could also be incorrect, inaccurate since it’s not checked• There’s a real risk of info overload, even if search engine’s

used properly; difficult to find relevant info

UNDESIRABILITY OF CERTAIN WEBSITES

• There’s always a risk of finding undesirable websites• There’s a risk of connecting to websites that aren’t genuine• Security risks

SECURITY ISSUES

• Passwords are used in many instances in the internet:• Accessing your email account• Carrying out online banking• Accessing social networking sites

• Passwords should be protected, could be done by:• Running anti-spyware software• Changing passwords on a regular basis• Passwords shouldn’t be easy to guess or break

AUTHENTICATION

• Used to verify data comes from a secure and trusted source• Forms of authentications include:

• Digital certificates• Biometrics• Magnetic stripe cards/id cards/passports

• Magnetic stripe cards have a magnetic stripe that is read by swiping the card through the reader• Contactless cards can be read from a distance• Some ID cards use holographic image (hologram)• Another form of security is having photographic image of the card user printed on the card• Many passports contain an RFID tag/chip, photograph and holographic image

ANTIVIRUS SOFTWARE

• Common features of antivirus software• Check software or files before they are run or loaded• Compares a possible virus against a database of known viruses• They carry out heuristic checking-checking of software for types of behavior that

indicates a virus• Any possible infected files or programs are put into quarantine that:

• Allows the virus to be deleted• Allows user to make the decision about deletion

• Antivirus software needs to be kept up to date• Full system checks need to be carried out once a week

AVOIDING VIRUSES WHEN ACCESSING THE INTERNET• One way to help prevent virus attacks is to avoid unknown or

suspicious websites• Look out for odd behaviors in URL• Don’t open emails from unknown sources

VIRUSES FROM HARDWARE DEVICES

• Possible to pick up viruses from device plugged into the computer• Even memory sticks or DVDs from friends could still be

infected

DATA PROTECTION ACTS

• Most countries have some form of data protection act (DPA)• DPAs are set up to protect rights of the individual about whom data is

obtained, stored and processed• There are general guidelines about how to stop data being obtained

unlawfully:• Don’t leave personal info lying around when not attended• Lock filing cabinets at the end of the day or when room is unoccupied• Don’t leave data on a computer monitor if it’s unattended• Use passwords and user ids, which should be kept secure• Make sure that anything sent in an email or fax

FAXES AND EMAILS

• 2 basic ways of sending a fax:• A physical fax (a dedicated machine connected to a

telephone line; requires recipient's number to be dialed before fax is sent)• Electronic fax (requires a network, such as internet, for fax

to be sent)

PHYSICAL FAX MACHINES

• Allows documents to be sent to another fax machine using telephone line• User places the document in the fax tray, lifts the receiver and dials the

fax number of the recipient and presses “send”• Electronic faxing has following advantages over traditional methods:

• Costs are reduced as there’s no need to buy a fax machine, ink/toner or paper• Transfers using electronic methods are encrypted, improved security• Transmissions are sent to an email account• No issue of a busy signal preventing the fax being sent

EMAILS

• Electronic email (email) is useful when sending attachments• Email can be sent to or from any device connected to

internet• Email requires an account with an ISP• Sending an email requires the email address, a subject line

any attachments if required

COMPARISON OF TRADITIONAL FAXES AND EMAILS

TRADITIONAL FAXES

• More likely to be intercepted since the document needs to be printed out, accessible to many people

• Signatures on faxes are accepted legally• Quality of the documents printed out can

be quite poor at times• If telephone line is busy then fax is delayed• In can be a slow process if several

documents are to be sent

EMAILS

• More secure than faxes• No need to print the document• The document’s usually of a much better

quality• Unlike paper-based faxes, documents received

can be modified or easily copied and pasted• Can be sent and received from any device tat

has internet• Much easier to send multiple recipients at the

same time• People are more likely to have access to email

accounts than a fax machine

VIDEO CONFERENCING• Video conferencing is a communication method using both video and sound• Carried out in real time and makes use of some form of network• Basic hardware includes:

• Webcams• Large monitors/television screens• Microphones• Speakers

• Few items to consider before a conference begins:• Essential to agree a time and date for the conference• Delegates in each conference room mist log in to the video conference system• The video conference set-up needs to be checked before meeting goes live• Webcams need to be placed in correct position• Microphones need be placed centrally• Important for one person to be the main contact in each conference room to make sure that

each delegate is heard

POTENTIAL ISSUES WITH VIDEO CONFERENCING• Potential time lag in responses/delays when talking• Jerking images• Can be very expensive to set up• There can be problems if the delegates live in different countries• Training people to use system correctly is costly and time consuming• It can be demotivating for staff if they believe ‘perks’ of their job is

international travelling• Whole system relies on a good network connection

ADVANTAGES OF VIDEO CONFERENCING

• People are in their own building, much easier to access documents or bring in ‘experts’ at key parts of their conference• Possible to hold conferences at short notice• Not travelling physically to meetings reduces costs:

• Reduced travelling costs• No need to pay for accommodation• Reduces the cost of taking people away from their work for two or three days to travel

• May be better rather than having delegates traveling to potentially unsafe places around the world

AUDIO CONFERENCING

• Meetings held between people using audio equipment• It can be done over telephone network, here’s the procedure:

• Organizer of phone conference is given 2 PINs by the phone company, 1 for him/her and second to the participants

• Organizer contacts all of the participants and inform their PIN and data• When phone conference’s about to start, organizer dials the conference phone number and

plugs his/her PIN• Participants then call the conference number and put in their PIN

• Possible to hold an audio conference using computers, making use of Voice over Internet Protocol (VoIP)

• If some users don’t have internet, they can join through their telephone numbers• Disadvantages: Drop out, Echoing, Very noisy line making it hard to understand

WEB CONFERENCING• Often referred to webinar, uses the internet to permit conferencing to take place• Multiple computers are used, allows the following meetings to take place:

• Business meetings to discuss new ideas• Presentations• Online education or training

• Delegates can leave or join as they wish• Main features include of web conferencing:

• Slide presentations using presentation software can be posted on the conference website in advance

• Possible for any delegate to draw or write on a ‘whiteboard’ using keyboard or mouse• Possible to transmit images or videos using webcam throughout the conference• Documents can be shared by uploading them to the website• Possible to chat verbally or by instant messaging

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