Computer Networks: Devices, LANs, WLANs, WANs

Objectives of Computer Networks

• Describe the use of various devices used to set up computer networks
• Describe the use of Wi-Fi and Bluetooth in networks
• Define the terms LAN, WLAN, and WAN and identify their characteristics
• Note the differences between LAN, WLAN, and WAN
• Identify a variety of methods of communication over networks
• Describe the advantages and disadvantages of the internet and intranets in business environments
• Understand the advantages and disadvantages of accessing the internet using different types of computer
• Understand and explain the need to use IDs and passwords
• Understand and explain the need for confidentiality and data security on computer networks
• Identify and explain the need for encryption and authentication techniques

What is a Network?

• A network consists of two or more computers or electronic devices
• They are connected to facilitate data exchange
• Networks allow computers to share files, exchange messages, and share resources like printers
• Connections are typically made using cables, but can also be achieved through radio signals (Wi-Fi), telephone lines (with modems), or satellite links for long distances

Why Use Networks?

• Networks facilitate easy sharing of files and data
• Resources such as printers and Internet connections can be shared
• Communication among network users is enhanced through email, instant messaging, and video conferences
• Central data storage on a file server allows for easy access and backup
• Workstations can access settings centrally managed
• Online services like shopping (e-commerce) and banking become accessible
• Access to a wide array of information is available for research purposes
• Different forms of entertainment, including games and video, can be accessed
• Online communities, such as MySpace and Facebook, can be joined

Why Not Use Networks?

• Computers become more vulnerable to hackers
• Network disruptions can make tasks difficult
• The risk of virus attacks increases
• Revealing personal information requires caution
• Users must avoid potentially harmful websites that may contain malware
• Information on the Internet may not always be accurate or reliable

Computers in a Network

• Client computers, or workstations, are the computers users interact with for their work
• Servers are powerful computers that provide services to client computers on the network
• Server services include centralized file storage, sharing hardware such as printers, controlling network access, and sharing Internet connections

Types of Network

• There are networks that don't involve computers

Local Area Network (LAN)

• A LAN confines its network to one building or site
• LANs are private networks belonging to an organization or business
• LANs typically use cables or low-power radio (wireless) for connections because they are geographically small

Wireless Local Area Network (WLAN)

• A WLAN is a LAN that uses radio signals (WiFi) instead of cables to connect computers
• A wireless switch or router with antennas is at the center of the WLAN
• The antennas send and receive data to the computers

Wide Area Network (WAN)

• A WAN extends over a large area
• A WAN is created by joining several LANs together, like when offices in different countries link their LANs
• WANs often use optical fiber cables, satellite radio links, and microwave radio links

Bluetooth (Personal Area Network)

• Bluetooth is a wireless networking technology designed for short-range connections
• Bluetooth aims to eliminate the need for cables that connect computers to devices like printers, mice, and keyboards
• Bluetooth devices use small, low-power radio transmitters and receivers
• When devices are in range, they detect each other and can be paired

LAN Topologies

• LAN topologies define the structure of a network

Bus Network

• It uses a long, central cable called “bus' to connect all of the computers
• Is cheap to install because it only requires one long cable
• Communication can be slow because all computers share the same cable
• A break in the central bus cable will halt the network

Ring Network

• Each computer is connected to a loop of cable in a ring network
• The network can manage a break in the ring cable, as all computers remain connected

Star Network

• Each computer is connected to a central device
• The central device is often a hub or switch and passes messages between the computers
• It is expensive to install
• It is very fast because each computer has its own cable
• A central device impacts the workings of the entire network
• The network will fail if the central device breaks
• Is the most common network topology

Hybrid Network

• A hybrid network combines two or more basic topologies

Networking Hardware

• Cables are needed to connect different devices to create a network
• Cables are still used in most networks to carry more data per second

Key Cable Network Types

• Fiber optic cables
• Coaxial cable
• Unshielded twisted pair

Network Interface Card (NIC)

• For a computer to connect to a network, it needs to have a network interface card (NIC)
• Modern computers typically have NICs on the motherboard, but some may require an additional expansion card

Hub

• A hub connects a number of computers to create a LAN
• Hubs are found at at the center of a star network and have cables plugged into it from each computer
• If a hub receives data, it resends it to every computer on the network, and is considered a “dumb” device
• Hub-based networks are not very secure because everyone can listen in to communications

Switch

• A switch connects computers to make a LAN
• Switches are found at the center of a star network, and they have cables plugged into it from each computer
• Switches are more 'intelligent' devices. When they receive a message, it checks who it is addressed to and only sends it to the specific computer
• Networks that use switches are more secure than those that use hubs, but are also more expensive

Router

• Routers connect two or more networks
• They join a local network to the Internet

Proxy Server

• Proxy servers share resources such as an Internet connection
• Other computers request web pages via the proxy server and then it sends it back to the computer that asked for it
• Used because additional software can be installed such as anti-virus and web filtering

Bridge

• A bridge is a network device that links two parts of a LAN together
• A router links a LAN to a WAN, such as the Internet
• Bridges link independent parts of a LAN so it acts like a single LAN

Firewall

• A firewall is a device or software that is positioned between your computer and other networks
• Its purpose is to protect an entire LAN from hackers on the Internet
• Firewalls block unauthorized connections and allow normal data to pass through

Modem

• Modems were used to connect to the Internet via telephone lines
• Telephone lines are designed to carry voices (analogue signals), not digital data
• The solution was to use modems which convert data for transmission

Key Terms

• The Digital to Analogue Converter (DAC) in the modem translates digital data into analogue signals for telephone lines
• The Analogue to Digital Converter (ADC) in the modem translates analogue signals from telephone lines back into digital data
• Modems convert computers to send signals from digital to analogue and from analogue to digital

Parts of a Webpage Address

• https://www.singaporeschools.ph/admission/ is an example of a webpage address

Internet vs Intranet

• A website address uses:
• Top Level Domain
• Second Level Domain
• Subdomain
• File name
• File Path
• Host name
• Protocol

Key Terms

• Https:// - Hypertext transfer protocol secure. A set of rules/protocol to transfer web pages securely.
• WWW - World wide web. An information system that operates over the internet
• Script - A set of instructions for computer Scripting language
• URL - Uniform Resource Locator is another term for the name of a website
• There is software that allows access to the internet
• You can access a website via URL or IP address

The Internet

• It's an international network that supports email, web browsing and text or voice chat

Internet vs Intranet: Webpages vs Websites

• Webpages contain text, images, sound, animations, and video
• Websites are linked together by hyperlinks that allow a user to navigate between webpages

Intranet Advantages

• Data is relevant to the user
• Data has been checked and validated by the organisation
• Smaller size makes communication and searching for information faster
• The structure will also be relevant to the organisation, so it will be easier for users to understand
• Ensure that all material is safer and appropriate

Intranet Disadvantages

• Limited resources when compared with the internet
• Limited range of views offered
• Expensive to setup and maintain as technicians need to be trained
• Staff need to be trained to upload material
• Limited access to/by customers and other organizations

Extranet vs Intranet

• Extranets are private internal networks with limited external access via the internet.
• Intranets are internal to companies or organizations
• Extranets and intranets provide limited information of relevance to specific external users
• Intranets block access to the internet to protect data
• The data stored locally on an intranet is very secure
• Extranets and intranets each have a layered method for access control

Internet vs Intranet (Differences)

• Security, data safety, access policies, etc, differentiate an intranet from the public wide open internet
• The data on an intranet is more relevant/reliable than information found on the internet

Internet vs Intranet (Similarities)

• Both are communication systems and networks
• Both use internet technologies and HTML to write the web pages
• Both are information systems

Accessing the internet

Dial-Up:

• Utilizes Dial-up Modems and a telephone line
• The advantage is that it is very cheap and only requires access to a telephone line
• The disadvantage is the slowest connection speed at 56 kbps while tying up the telephone line

Fibre Optic Cable

• Utilizes a cable modem
• The advantage is a very fast and stable connection that does not rely on the telephone line
• The disadvantages are they are often available only in urban areas

Broadband (DSL)

• Utilizes an ADSL Modem,
• The advantages are fast connections with an “always on” service
• One disadvantage is that heavy users can exceed limits
• Broadband is delivered via telephone connections
• The disadvantage is reduced speeds for users during peak demand

Mobile Broadband

• Utilizes phone data plans and a mobile phone with data
• Provides mobile access at any location for a fee

IP Address

• Internet Protocol address
• Consists of unique identifier
• IP addresses must be different for each device on a network
• All devices connected to the internet use IP addresses
• This determines the electronic location of the device

Purpose of a Routing Table

• Used to determine where data packets will be directed
• Stores route information
• Stores IP addresses

Protocols associated with Internet/Intranet

• HTTP/HyperText Transfer Protocol is used to transfer data between a webserver and the browser
• HTTPS/ HyperText Transfer Protocol Secure variant, is a secure version with data transfer between a webserver and the browser
• FTP/File Transfer Protocol transfers files between computers or websites
• VOIP/Voice Over Internet Protocol makes phone calls over the internet
• SSL/TLS (Secure Sockets Layer/Transport Layer Security) Determines variables of the encryption
• SMTP/Simple Mail Transfer Protocol A communication protocol for email
• SLS/Service Level Specification is a protocol used on the internet

Computer Networks in Business Environments

• Networks handle payments, send invoices, order materials, pay employees, deposit money and calculate finances

School management systems

• Used for School library, human resources, site management, finance, and many other systems

Booking systems Advantages:

• Individual seats and showings can be booked and payments can be made online
• You do not have to visit the cinema/theatre to book
• Returning customers details are saved, and theatres can plan ahead

Booking systems Disadvantages

• Things can be booked quickly reducing options
• Lack of Internet access can prevent bookings
• System crashes or duplicates create transaction errors

Banking systems Advantages:

• Accessed via ATM anywhere in the world and via internet
• Transactions can be done remotely
• Money moved between account quickly
• payroll can be set to benefit employer and employee

Banking systems Disadvantages

• Banks are distant reducing customer interaction
• Fraud via electronics increases
• Lack of Internet access reduces service benefits

Library system Advantages

• Renewed remotely with reminders via email or text
• Membership automated and cards not needed
• Books borrowed from other libraries

Library system Disadvantages

• People can miss out on books if they are renewed remotely
• traditional browsing is less helpful if most books are not stored in store

Expert System

• It's a computer software that attempts to act as a human expert on a particular subject area
• They are often used to advise or advisee non-experts
• Their function is used where expert is unavailable or might be to expensive to employ

How are expert systems created?

• Experts a interviewed and their knowledge is collected.
• Knowledge is organized and stored.
• This allows the knowledge base to be searched by the user.

Explanation/User Inferface

• This allows the user to communicate with the expert system
• Includes, text boxes, Check boxes/ option buttons, and Submit buttons Finally the expert system is tested to make sure that the correct answers

Elements/parts of an Expert system

• Inferface
• The system allows the user to ask their query and receive a response.
• Works like a search engine,
• Follows rules to get answers from the knowledge base by reasoning.
• Includes a Knowledge database with checked, stored and retrieved

What is a Rules Base

• Made up of inference rules that are use reason and make decision Example: IF the country United Kingdom AND its name begins with W, THEN it must be Wales.
• the system Explains to the user the reasoning behind the results they have been given.

Examples of Expert System

• Mineral Prospecting system
• Car engine fault diagnosis
• Medical diagnosis systems
• Chess and strategy game systems
• Financial planning systems
• Route scheduling for delivery vehicles
• Plant and animal identification system

Case Studies on Expert Systems

• Expert systems use analysis in the medical sector
• Help troubleshoot problems in companies in the telecommunications industry
• Assist finical planning systems
• Used for analysis and quality in Manufacturing

Methods of Electronic Communication:

• Email
• Most common method of communication in business context
• SMS text messaging Short Message Service is a designed for mobile phone networks around the world
• Real time communication built into social networking applications
• Video and audio conferencing
• Internet-based system based on streaming live video and audio between users
• Audio Conferencing
• Audio technology to to access location world wide
• The internet - Users can share electronic content with the others in the meeting. Voice Video and more over internet

Social Media and Networks

• Blogs (weblog)
• Online journals that are frequently updated
• Content is presented in chronological order
• Wikis use collaboration via online website tools
• Any member of the wiki can add and edit content
• Use of “Tweets” a messaging social media platform

Principles of Data Protection Act

• There are rules that protect individual privacy when it comes to internet data.
• There standards to ensure that Data kept is safe and lawful, accurate with limited transfer
• Parental consent required for processing personal data of children including online services

Personal Data

• Personal data is data relating to an individual/person that can be identified

Examples are Data protection

• Name, address, date of birth, medical and criminal records
• Religious or philosophical beliefs
• Trade-union membership record, genetic data, IP address, racial identity

Key Point

• The person can be identified so data as it links to them should safe
• someone gets access to the data they can attack the user
• it could lead to home burglaries since the user has revealed person data
• It Protections are put in place