Chapter 6 - Part 2

6.4 Internet in Action

By Klea h

Network Architecture

• In its simpliest form, the internet is just a large collection of interconnected devices (nodes) like desktop computers, laptops, tablets, phones, printers, cameras, routers, Wi-Fi access points, etc

• Devices connect either directly or indirectly.

• Any 2 devices are able to "communicate" by transmitting a digital signal along the appropriate medium (copper wire, fiber optic cable, radio wave transmission, etc.).

Client-Server Model

​The client-server model works in 3 steps:

• The client (like a computer or smartphone) connects to the network and sends various requests (e.g., to load a webpage or submit data).

• The server receives the requests, processes them, and sends back the requested data (like a file, webpage, or update).

• This model supports both client-side pull (you request info) and server-side push (the server sends info automatically).

Multiple Choice

Which of the following best describes how the client-server model operates on a network?

• The server initiates all requests and the client only responds when data is received.

• The client and server are identical systems that simultaneously exchange data.

• The client requests services or data from the server, which processes the request and returns the appropriate response.

• The client processes all network requests locally without needing to communicate with a server.

Packet Switching

Packet switching is the method the internet uses to send data. Instead of sending a file all at once, it breaks the data into small pieces called packets.

Each packet:

• Contains part of the data (like a puzzle piece)

• Includes instructions on where it's going and how to reassemble the message

Packets travel separately across the network and may take different routes. Once they all arrive, they’re put back together in the correct order.

It’s faster, more efficient, and helps avoid delays or slowdowns if one path is busy.

Multiple Choice

Packet switching is the method by which information is transmitted through routers on the internet. Data is split into packets which may be sent by multiple different routes to the destinations. The diagram in the PICTURE represents a series of routers through which packets can be sent.

If packets have an origin of “A” and a destination of “H,” which is NOT a path that a packet might take?

•  

  A to B to F to G to H

•  

  A to B to E to H

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  A to C to B to D to F to G to E to H

•  

  A to F to G to H

Speed & Performance

• Bandwidth = how much data can be sent per second (like the width of a pipe).

• Latency = how long it takes data to travel (like a delay or lag).

• A good internet experience has high bandwidth and low latency.

Multiple Choice

What does it mean for the routing of the Internet to be fault tolerant and redundant?

• If one path for data transmission is blocked or corrupted, data can follow another path.

• If the Internet goes down, packets of information will still be sent while “offline.”

•  There are no issues with routing information on the internet because protocols and high standards have made for faultless routing.

• There is only one path for data to travel from one device to another device on the Internet.

Multiple Choice

Students recently created a Gaming Club at their school. On Friday every week, students bring in their gaming consoles (Xbox, Playstation, etc) and they play their favorite games with other users online. However most of the students report that there is a lot more lag (delay in the actions of the controller and in game actions) when playing at school than when playing at home. Which of the following is most likely to be the issue students are having in their Gaming Club?

•  

  The bandwidth of the school’s internet connection is lower than the bandwidth of each of the students’ home internet connections.

•  

  At the gaming club, many more people are using the same internet connection than in a typical home, meaning the bandwidth available to each user is less.

•  

  The gaming consoles are unable to use as much RAM when used at school.

•  

  Friday night is a typical time at which most gaming consoles install updates. As these updates cannot be postponed the consoles will always run slower on a Friday night.

​​Routing and Nodes

• Routing is how data travels from sender to receiver through many devices (routers, gateways, switches).

• If one path is busy or down, the data finds a new route — this is routing redundancy.

• This makes the internet scalable, so it can work efficiently as more devices are added.

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Multiple Choice

A major connection in a network is damaged so that information can no longer be sent through the connection. If full communication on the network was able to continue, which of the following characteristics would the network be said to have?

• Fault-tolerant (or redundant) routing

• A hierarchical naming system

• Support for multiple protocols

• A server-client model

6.5 Communication Protocols

The Internet works because of protocols—rules that define how computers communicate. These protocols are essential for transmitting emails, loading web pages, sending texts, and more.

*protocol: A set of agreed-upon standards that specify the proper formatting of data, communication procedures, behavior and handling of information between any two networked components.

Examples of Protocols	​
​	Labels and delivers data like an address on a letter
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​	​
​	​
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​	Sends text messages (limited to 160 characters)
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Protocols ensure the internet functions reliably, securely, and across different systems. They allow innovation (like APIs) while maintaining a shared language between billions of devices.

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Multiple Choice

Which of the following is NOT a use of application programming interfaces (APIs)?

• Justifying a program’s correctness.

• Allowing software components to communicate.

• Simplifying complex programming tasks.

• Sharing a library of available procedures.

Multiple Choice

The IETF (Internet Engineering Task Force) is responsible for developing and overseeing internet standards. Which of the following is not a common protocol maintained by the IETF?

• UDP

• GPS

• IP

• SMTP

Multiple Choice

The architecture of the internet follows the end-to-end principle. This means that the verification and interpretation of data happens only at the endpoints: nodes passing on data packets do not know what they contain or if the data being sent is all received. Which of the following protocols can be used by the endpoints of a network following this principle to ensure the completeness of the transmission of data?

• TCP

• IP

• UDP

• HTTP

TCP/IP MODEL

1. The Link Layer: handles physical or wireless connections between devices. It makes sure your device can connect to the internet through cables or Wi-Fi.

2. The Transport Layer: This layer controls how data moves through the network. It uses TCP and UDP protocols.

3. The Internet Layer: decides where data goes. It uses IP (Internet Protocol) to label and route packets.

4. The Application Layer: This layer deals with specific tasks like:

   • HTTP/HTTPS for loading websites

   • SMTP for sending emails

   • FTP for downloading/uploading files

6.6 Internet Protocols - how devices communicate over the internet

What Is an IP Address?

• An IP address is a unique number assigned to each device on the internet like an address for your computer or phone.

​IPv4:

• Format: 4 numbers each (0–255) separated by dots (e.g., 192.168.1.1)

• Uses 32 bits = ~4.3 billion possible addresses

• Due to the explosion of internet-connected devices, IPv4 addresses are running out

IPv6:

• Format: 4 values each of digits(0-9) and letters (A-F)

• Uses 128 bits = 340 undecillion (that’s 340 billion billion billion billion!) addresses

• Can handle the growing number of devices, including IOT devices.

Multiple Choice

What must devices that communicate with one another on the internet have in common?

• Use the same internet protocols.

• Be in the same physical location.

• Be the same brand .

• Use the same internet service provider.

Multiple Choice

Which of the following is NOT a valid IP address that is consistent with the IPv4 standards?

• 8.8.8.8

• 4.15.207.256

• 12.144.65.88

• 10.10.129.242

​DNS: Domain Name System

Understanding IP and DNS helps explain how billions of devices talk to each other across the globe. It also highlights why new technologies like IPv6 are crucial to support our growing digital world.

​Humans remember website names (like google.com) better than long numbers.

• DNS translates domain names into IP addresses (just like a phone book for websites).

• When you type a URL, your browser asks DNS to find the matching IP address so it knows where to go.

Multiple Choice

Website IP addresses such as 74.125.65.91 and 72.21.211.176 are difficult to remember. When browsing the internet therefore users usually enter URLs such as http://www.youtube.com and http://www.amazon.com instead. The use of which internet protocol allows internet users to type URLs instead of IP addresses when navigating to a website?

• DNS

• HTTP

• URL

• IP

6.7 Caesar Cipher

• One of the earliest encryption methods (used by Julius Caesar)

• This schema is known as a substitution cipher because it substitutes each letter of the original, unencrypted message (the plaintext) with a corresponding letter in the final, encrypted message (the ciphertext).

• Example (shift of 3):

  • Plaintext: this is a caesar cipher

  • Ciphertext: qefp fp x zxbpxo zfmebo

Multiple Choice

The following message has been encoded using a Caesar cipher of shift −3: bibsbkp ybkze. Decode this message.

• elevens bench

• Captain crunch

• blowers hench

• algebra hands

Multiple Select

Which of the following open source software licensing scenarios are most likely to raise ethical/legal issues? Select two.

•  A software developer takes code used for an open source modeling software, renames it without changing any of the code, removes the attribution to the original creator and then shares it with friends.

•  A software developer uses a piece of open source code released and combines it with their own code. The new combined code is then licensed for commercial use.

•  A software developer takes code used for an open source email client and edits it to create their own modified version of the email client. The original license terms state that derivatives must be released under the same license, but as the developer used their own code as well they decide to release the software using a proprietary license instead.

•  A small business owner downloads open-source accounting software for her business. She rates the program highly, so decides to share it on a peer-to-peer file-sharing network so more people can download it.

Why Use Two Keys?

With symmetric encryption, you need to share the same key with the other person — which can be risky if intercepted. With asymmetric encryption, you never send your private key, so it’s safer.

Think of a public key like a locked mailbox with a mail slot:

• Anyone can drop a message into the slot (encrypt a message with your public key).

• But only you have the key to open the mailbox (your private key) and read it.

​Sender (Alice) encrypts the message using a key

​Message is sent (and is possibly seen by others like “Eve”)

​Recipient (Bob) uses the correct key to decrypt it

Multiple Choice

Consider the process of encoding and decoding a message using the following Caesar cipher encoding scheme in which the plaintext and ciphertext alphabets are offset by 4 positions, as shown in the picture:

Which of the following encoded ciphertext strings decodes to an original plaintext message of "secret"?

• wigvix

• owujwl

• etsecr

• oaynap

6.8 Cybersecurity

Cybersecurity is all about protecting computers, networks, and data from attacks, theft, or damage. It includes tools like antivirus software, firewalls, password protection, and secure networks.

​​The CIA Triad (Core of Cybersecurity - foundation of all secure systems)

​Authentication

• Authentication means verifying who someone is before giving them access.

• Strong passwords and multifactor authentication (like a code + fingerprint) help keep accounts secure.

Multiple Choice

Which of the following is not part of the CIA Triad?

• Authentication
• Integrity
• Confidentiality
• Availability

Multiple Choice

Which of the following is most likely to be a phishing attack?

•  A store manager asks you to use his personal laptop to login to your bank account to show that you have the funds necessary to buy that particular item.

•  A credit card company calls to inform you to check your account online to verify transactions.

•  An email is sent to you from your internet service provider indicating that there is suspicious activity coming from your IP address.

•  You get a letter in the mail, addressed to you, asking you to donate to the local fire department by dropping by the fire station and writing them a check.

Multiple Choice

Which of the following best defines confidentiality in context with information and data?

•  

  The ability to limit access to information to a certain set of users

•  

  The certainty that information is accurate

•  

  The confirmation that a company will not sell your information to others

•  

  The reliability of access to information

​Common Cyber Threats

• DDoS Attack: Overloads a website with traffic to shut it down.

• Malware & Viruses: Harmful programs that damage or take control of a device.

• Phishing: Tricking someone into giving away private info through fake emails or sites.

• Keylogging: Secretly records keystrokes to steal passwords and sensitive info.

• Rogue Wi-Fi: Fake public networks that steal your data.

How to Stay Safe

• Use antivirus software and firewalls

• Update your software regularly

• Avoid suspicious links and downloads

• Review app permissions

• Be cautious on public computers and Wi-Fi networks

Multiple Choice

Which of the following is a good practice to prevent your password from being vulnerable to attacks?

•  

  Create your passwords based on some algorithm that helps generate a password that uses a combination of letters, numbers and symbols

•  Always use the same passwords across different sites so that you can easily remember them.

•  Make sure to follow the links provided in emails to help you reset your passwords.

•  Use simple passwords that use basic words and important numbers like your birthday.

6.9 World Wide Web

The World Wide Web (WWW) is a way to share and access content over the Internet using web browsers and hyperlinks. It is not the same as the Internet, which is the physical network of connected computers.

Tim Berners-Lee invented the Web in the early 1990s to make information easier to access and share globally.

• The Web uses HTTP, HTML, and URLs to link and display pages.

• Hyperlinks connect web pages in a non-linear way, letting users jump freely between content.

Main Web Tools:

• Web Browser: lets users view websites

• Web Server: stores and delivers website content

• HTML: formats web page content

• URL/URI: the address of a web page

• HTTP: the protocol used to request and load web pages

Why It Matters:

• The Web changed how we learn, communicate, and do business.

• Berners-Lee made the Web free and open, encouraging global access and innovation.

6.10 Distributed Computing

Distributed computing is when multiple computers work together on a problem by sharing tasks. Instead of one computer doing all the work, many computers process smaller parts in parallel, saving time and boosting efficiency.

• Botnets (The Dark Side): Not all distributed systems are good. Botnets are a network of private computers infected with a malicious software and controlled as a group —all without the owner's knowledge.

• bitcoin mining: the processing of transactions in the digital currency system, in which the records of current Bitcoin transactions, are added to the record of past transactions.

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SETI@Home Example: lets people donate unused computer power to help scientists search for signals from space. It’s part of the BOINC project, which supports many research efforts using this model.

COMPUTATIONAL MODELS

• Sequential computing: operations are performed in order one at a time.

• Parallel computing: the program is broken into multiple smaller operations, some of which are performed simultaneously.

• Distributed computing: multiple connected devices are used to solve a problem or run a program

6.11 Internet of Things (IoT)

The Internet of Things (IoT) refers to everyday objects—like smart watches, fridges, cars, and thermostats—that are connected to the internet to send and receive data. These smart devices work together to improve convenience, efficiency, and automation.


Examples of IoT in Action:

• GPS systems for real-time navigation

• Sensor networks to monitor light, temperature, or sound

• Smart homes that auto-adjust lights and thermostats

• Healthcare devices that track steps, heart rate, or sleep

While IoT brings comfort and efficiency, it also raises security and privacy concerns, since more devices mean more potential for cyber threats.

Multiple Select

An electric grid was originally developed for power companies to distribute energy to customers and then bill them once a week for their usage. However, with the ever developing energy demands of the 21st century, the smart grid introduces a two-way dialogue where electricity and information can be exchanged between customers and utilities. It is a developing technology to help make the grid more efficient, reliable, secure and greener. Which of the following is an effect of the smart grid? Select two answers.

•  The smart grid allows for the creation of services which customers can use to access data about their electric use online.

•  The data provided by users on the smart grid could be used by energy providers to improve their models predicting when additional energy may need to be supplied to the grid.

•  After power outages, because of the complex nature of the computers and technologies involved, it will take longer to restore the electricity.

•  The cost for electric will eventually increase because of the increased need for operations and management of this new smart grid.

Multiple Select

GPS has fostered many benefits in our society, but has also added some risks. Which of the following are potential risks associated with GPS? Select two answers.

•  GPS navigation systems can distract drivers and sometimes cause accidents on the road.

•  GPS can be used by police in order to track down cars, cell phones, etc in order to locate stolen vehicles and devices.

•  GPS navigation systems are not always up-to-date, and therefore give outdated route information which can result in users becoming lost.

•  GPS is used by some backpackers in order to help them navigate the wilderness terrain.

6.12 Ethics of Autonomous Technology

Autonomous technology refers to smart systems (like self-driving cars) that make decisions without human input. As these technologies become more common, ethical and legal questions arise.

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• Can machines make ethical decisions like humans?

• What happens when autonomous systems must choose between two harmful outcomes (e.g., the Trolley Problem)?

• Who is responsible if a self-driving car causes an accident—the car, the owner, the programmers, or the manufacturer?

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​A moral dilemma: should you sacrifice one person to save five, even if the sacrifice requires you to actively cause harm?

​The Trolley Problem

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Broader Legal and Ethical Concerns:

• Biased algorithms

• Data privacy

• Misinformation spread

• Digital divide (tech access inequality)

• Use of technology to harm or manipulate others

Programmers must design with ethics in mind, and lawmakers must understand tech to create fair regulations. Ethics and law need to evolve alongside innovation.