Основи комп'ютених мереж

Basics of computer networks

Introduction to Networking:
- Computers communicate with each other over a network by sending and receiving data.
  - Local area networks (LANs) are used for communication within a small area, like an office, while wide area networks (WANs) cover larger geographical areas, like connecting offices in different cities.
  Real life examples
  - LAN: Computers in an office sharing files and printers.
  - WAN: Connecting multiple branches of a company across different cities.
  Examples related to the topic
  - Sending an email from one computer to another.
  - Streaming a video from a server to your device.
  Want to know more? Google these points:
  - How do LANs and WANs differ?
  - How does data travel between computers on a network?
  Later we'll discuss
  - TCP/IP protocol suite
  - IP addresses
- Differentiating between local area networks (LANs) and wide area networks (WANs).
OSI Model:
The OSI model is a framework that defines how different devices communicate over a network. It consists of seven layers, each with its own specific functions. This model helps in understanding the flow of data between devices and enables interoperability between different network technologies.
- OSI Model basics
  - Real life examples
    Imagine sending a letter to a friend. The process involves writing the letter (application layer), putting it in an envelope (transport layer), addressing the envelope (network layer), sending it through the postal system (data link layer), and finally delivering it to your friend (physical layer).
    Examples related to the topic
    When you visit a website, your web browser (application layer) sends a request to the server (transport layer) using the IP address (network layer). This process is known as the client-server communication model. The server then receives the request, which includes information about the specific page or resource you are trying to access. It processes the request by retrieving the necessary data or executing the required actions. Once the server has completed its processing, it generates a response, which includes the requested data or the result of the executed actions. The response is then sent back to your web browser through the same layers of the communication model. This process ensures that the information you requested is efficiently transmitted from the server to your browser, allowing you to view and interact with the website's content.
- Understanding the purpose and functions of each OSI layer:
  The OSI model is a framework that helps us understand how devices communicate over a network. It consists of seven layers, each with its own specific functions. Here's a brief description of each layer:
  - Application Layer: This layer deals with user interaction and provides services for applications to access the network. It includes protocols like HTTP, FTP, and SMTP.
    Real life examples
    Sending emails or browsing websites.
    Examples related to the topic
    Using the HTTP protocol to request web pages.
  - Presentation Layer: This layer is responsible for data formatting and encryption. It ensures that data from the application layer is correctly interpreted by the receiving device.
    Real life examples
    Converting a file from one format to another
    Examples related to the topic
    Encrypting data before sending it over the network.
  - Session Layer: This layer establishes, manages, and terminates connections between devices. It allows devices to have conversations and ensures data integrity.
    Real life examples
    Making a phone call or video conference.
    Examples related to the topic
    Establishing a connection between two devices for data transfer.
  - Transport Layer: This layer handles end-to-end communication and ensures reliable delivery of data. It breaks data into smaller packets and reassembles them at the destination.
    Real life examples
    Sending a package through the mail.
    Examples related to the topic
    Splitting a large file into smaller packets for transmission.
  - Network Layer: This layer deals with network addressing and routing. It determines the best path for data packets to reach their destination.
    Real life examples
    Using a GPS navigation system to find the most efficient route.
    Examples related to the topic
    Using IP addresses to route data packets over the internet.
  - Data Link Layer: This layer provides error-free transmission of data frames between devices on the same network. It also handles flow control and error detection.
    Real life examples
    Sending a letter through the postal service.
    Examples related to the topic
    Transmitting data frames between devices connected by Ethernet.
  - Physical Layer: This layer deals with the physical transmission of data over the network. It includes specifications for cables, connectors, and other hardware.
    Real life examples
    Speaking to someone face-to-face.
    Examples related to the topic
    Transmitting electrical signals or light pulses through network cables.
  - Want to know more? Google these points:
    What are the functions of the OSI model layers?
    How does data flow through the OSI model?
    How does each layer of the OSI model work?
    What are the advantages of using the OSI model for network communication?
  - Later we'll discuss:
    TCP/IP protocol suite
    IP addresses
TCP/IP Stack:
- Learning about the TCP/IP protocol suite, which is fundamental to the Internet.
  The TCP/IP protocol suite is like a set of rules that computers follow to talk to each other on the internet.
  - Real life examples
    Imagine the TCP/IP suite as a recipe book for making a delicious dish. Each step (protocol) is essential to create the final meal (data transfer).
  - Examples related to the topic
    In this "recipe," TCP ensures the ingredients (data) are mixed properly, and IP is like the cooking instructions, making sure the dish (data) reaches its destination.
  - Want to know more?
    OSI Model, TCP vs. UDP, IP addressing.
  - Later we'll discuss
    Socket programming, network troubleshooting.
  - Exploring the key protocols within TCP/IP, including TCP (Transmission Control Protocol) and IP (Internet Protocol).
    TCP and IP are like a dynamic duo - TCP ensures data arrives safely, and IP guides it to the right destination.
    Real life examples
    Think of TCP as a trustworthy delivery person who checks the package (data) to make sure nothing is broken. IP is the address on the package, telling the delivery person where to go.
    Examples related to the topic
    Before sending the package (data), TCP and IP have a quick chat (three-way handshake) to make sure everything is set for a smooth delivery.
    Initiation (SYN): The client sends a SYN packet to the server to start the connection.
    Acknowledgment and Agreement (SYN-ACK): The server responds with a SYN-ACK packet, acknowledging the client's request and signaling its willingness to establish a connection.
    Final Acknowledgment (ACK): Upon receiving the server's SYN-ACK, the client sends an ACK packet to confirm the connection is established.
    The three-way handshake is like a polite conversation before exchanging information. It ensures that both the client and server are aware of each other's presence, willing to communicate, and ready to start the data transfer. This process helps in preventing data loss and ensures a reliable and synchronized connection between the devices.
    Want to know more?
    TCP flags, IPv4 vs. IPv6, subnetting.
    Packet loss, retransmission.
IP Addresses:
- IP addresses are unique identifiers assigned to devices on a network. They allow devices to send and receive data to and from other devices. It's like a phone number for the internet.
  - Real life examples
    Each house having a unique address in a neighborhood.
  - Examples related to the topic
    Devices on a network having unique IP addresses to communicate with each other.
  - Want to know more? Google these points:
    How are IP addresses assigned?
    What is the difference between IPv4 and IPv6?
  - How are IP addresses assigned?
    IP addresses are assigned to devices on a network by network administrators or Internet Service Providers (ISPs). There are two main types of IP addresses: static and dynamic. Static IP addresses are manually assigned to devices and remain the same over time. Dynamic IP addresses are automatically assigned by the network's DHCP (Dynamic Host Configuration Protocol) server and can change periodically. IP addresses are essential for devices to communicate with each other on a network, similar to how each house has a unique address in a neighborhood.
    Real life examples
    Regional postal services distributing address blocks to local post offices.
    Assigning a specific parking spot to each employee in an office building.
    Imagine going to a coffee shop and connecting your laptop to their Wi-Fi network. Instead of manually configuring your IP address, DHCP (Dynamic Host Configuration Protocol) automatically assigns one to your device.
    Examples related to the topic
    Assigning a unique IP address to each device connected to a home Wi-Fi network.
    IP addresses are allocated globally by regional Internet registries (RIRs) who distribute them to Internet Service Providers (ISPs) or organizations within their region. This hierarchical system ensures efficient distribution of IP addresses worldwide.
    Want to know more? Google these points:
    How does DHCP work?
    How are IP addresses allocated globally?
  - Differentiating between IPv4 and IPv6 addressing:
    IPv4 and IPv6 are two different versions of the Internet Protocol, which is responsible for assigning unique addresses to devices on a network.
    Real life examples
    Imagine a neighborhood where houses are assigned street addresses. IPv4 would be like using a 4-digit numbering system, which limits the number of unique addresses available. IPv6, on the other hand, would be like using a 6-digit numbering system, allowing for a much larger pool of unique addresses.
    Examples related to the topic
    IPv4 addresses are structured as 32-bit, divided into four groups of numbers separated by periods. IPv6 addresses, on the other hand, are structured as 128-bit, divided into eight groups of hexadecimal numbers separated by colons.
    IPv4 addresses are represented in a dotted-decimal format, such as 192.168.0.1. IPv6 addresses are represented in a hexadecimal format, such as 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
    Want to know more? Google these points:
    What are the differences between IPv4 and IPv6?
    How are IPv4 and IPv6 addresses structured?
    Later we'll discuss:
    TCP/IP protocol suite
    IP addresses
Subnetting:
- Learning how to subnet IP addresses to efficiently allocate and manage network resources.
  Subnetting is like dividing a big neighborhood (network) into smaller blocks for easier management. It helps in organizing and efficiently using IP addresses.
  - Real life examples
    Imagine a large field (network) being divided into smaller plots (subnets), each assigned to a different purpose.
    Think of a subnet mask like a city map. A mask of 255.255.255.0 means you can move freely within a city block (subnet), but crossing streets (subnets) requires more effort.
  - Examples related to the topic
    Subnetting allows network administrators to allocate specific ranges of IP addresses to different departments or devices.
  - Want to know more?
    VLSM (Variable Length Subnet Masking), subnetting tools, subnet design best practices.
  - Later we'll discuss
    CIDR notation, subnetting in IPv6.
- Subnet Masks
  Subnet masks act like fences, separating the network and host portions of an IP address. Common subnet masks include 255.255.255.0 and 255.255.0.0.
  - Real life examples
    Think of a subnet mask like a city map. A mask of 255.255.255.0 means you can move freely within a city block (subnet), but crossing streets (subnets) requires more effort.
- Public and Private IP Addresses
  Public IP addresses are like street addresses that are visible to the outside world, while private IP addresses are like apartment numbers within a building, hidden from the public.
  - Real life examples
    Think of a public IP address as your home address, and private IP addresses as apartment numbers within your building. Another example is a small village that internally uses its own numbering system for houses, but most houses also have a public address.
    Your home's public IP address is what allows your computer to connect to websites and servers on the internet.
  - Examples related to the topic
    Public IP addresses are used for devices that need to communicate with the internet, while private IP addresses are for devices within a local network.
    Common private IP address ranges include 192.168.x.x, 172.16.x.x–172.31.x.x, and 10.x.x.x.
  - Want to know more?
    NAT (Network Address Translation), IP address allocation policies, IPv6 addressing
- Other IP Addresses
  Other IP addresses may refer to reserved or special-use addresses. These include loopback addresses, multicast addresses, and reserved ranges for documentation.
  - Real life examples
    The loopback address (127.0.0.1) is like talking to yourself in a conversation. It's used for testing network functionality on your own device.
  - Want to know more?
    Reserved IP address ranges, special-purpose addresses like APIPA (Automatic Private IP Addressing).
    Multicast communication, the significance of loopback addresses in troubleshooting.
Routing:
- Exploring the basics of routing and how routers facilitate communication between different networks:
  Routing is the process of directing network traffic from one network to another. Routers are devices that help facilitate this communication by determining the best path for data to travel between networks. They use routing protocols to exchange information and build a map of the network. Routers analyze the destination IP address of incoming data packets and forward them to the appropriate network. They ensure that data reaches its intended destination by making decisions based on routing tables. Without routers, networks would not be able to connect with each other.
  - Real life examples
    Think of routing as planning a road trip. You use a map or GPS to find the best route to your destination, avoiding traffic and roadblocks.
  - Examples related to the topic
    When you access a website hosted on a server in a different country, routers help route your request through various networks to reach the server.
    Routers play a crucial role in the internet, ensuring that data packets are directed to the correct networks worldwide.
    Trick your computer into thinking that it is opening your own page instead of Google by adding an entry to the ‘hosts’ file like this: 127.0.0.1 google.com. This allows you to test web applications locally. However, please note that this change only affects your computer and does not affect other devices on the network or external routers when resolving .
  - Want to know more? Google these points:
    How do routers work?
    Network topologies
    Routing protocols
    What are routing protocols?
    What is the ‘hosts’ file?
DNS (Domain Name System):
- Understanding the role of DNS in translating domain names to IP addresses.
  DNS (Domain Name System) acts like a phone book for the internet, translating human-friendly domain names (like ) into computer-friendly IP addresses.
  - Real life examples
    Think of DNS like a librarian who helps you find a book (website) by translating its title (domain name) into the right section (IP address).
  - Examples related to the topic
    When you type a website's name, DNS quickly looks up the address, so you reach the correct online destination.
    A common example is when you have issues opening certain pages on your computer, while others open without any problems. In such cases, try changing your DNS provider in the settings. Two common options are 8.8.8.8 and 8.8.4.4, both owned by Google.
  - Want to know more?
    DNS resolution process, recursive vs. authoritative DNS servers.
- Exploring the hierarchical structure of the DNS.
  The DNS is organized in a hierarchical structure, with different levels of authority. It starts with the root domain, followed by top-level domains (TLDs), and then individual domain names.
  - Real life examples
    Imagine a large organization with departments and teams. The root domain is like the CEO, TLDs are department heads, and individual domain names are team members.
  - Examples related to the topic
    The root domain is represented by a dot (.), and it leads to TLDs like .com, .org, and country-specific ones like .uk or .jp.
    Some domains can be used only for some particular purposes like edu,
  - Want to know more?
    DNS zone files, authoritative name servers, DNS delegation.
    Anycast DNS, the role of registrars in domain management.
- Domain Registration Process
  Owning a domain involves registering it through a domain registrar. You choose a unique domain name, check its availability, and pay a registration fee to the registrar for a specified period, usually annually.
  Real-life examples
  - Registering a domain is like reserving a unique business name with the government. Once registered, it's officially yours.
  - Certain domain extensions, also known as TLDs, have specific purposes and restrictions. Examples include .edu for educational institutions, .gov for U.S. government entities, .mil for the U.S. Department of Defense, .int for international organizations, .museum for museums, .aero for the aerospace industry, and .coop for cooperative associations. These are some specialized domain extensions.
  - Some domain extensions can only be reserved under certain circumstances. For example, the .ua extension can only be obtained if you have a trademark registered in Ukraine.
Ports and Sockets:
- Learning about ports as communication endpoints in networking.
  Ports are like doors on a computer. They allow different applications to send and receive data. Each port number is associated with a specific type of service or application.
  - Real life examples
    Think of ports as apartment numbers in a building. Each apartment (port) is a different residence (service) inside the building (computer).
  - Examples related to the topic
    Port 80 is commonly used for web traffic, like opening the front door for visitors to a website.
  - Want to know more?
    Well-known port numbers, dynamic vs. static ports.
  - Later we'll discuss
    Port forwarding, security considerations in port usage.
- Port Numbers
  Port numbers range from 0 to 65535. Well-known ports (0-1023) are reserved for standard services like HTTP (80) and FTP (21). Registered ports (1024-49151) are for user-registered services, and dynamic or private ports (49152-65535) are for temporary purposes.
  - Real life examples
    Think of port numbers like TV channels. Well-known channels (ports) are for common shows (services), while you can choose other channels (ports) for your personal preferences.
  - Examples related to the topic
    Port 443 is commonly used for secure web browsing (HTTPS). Port 80 is assigned to HTTP (Hypertext Transfer Protocol).
  - Want to know more?
    IANA's list of assigned port numbers.
  - Later we'll discuss
    Port scanning, port exhaustion.
- Understanding sockets as a mechanism for processes on different devices to communicate.
  Sockets are communication endpoints in a network. They enable processes on different devices to send and receive data. A socket consists of an IP address and a port number.
  - Real life examples
    Imagine a telephone as a socket. You have your phone number (IP address) and a specific extension (port) for communication.
  - Examples related to the topic
    A server socket might be waiting for calls (connections) on a specific phone line (port).
  - Want to know more?
    Types of sockets (stream vs. datagram), socket programming.
  - Later we'll discuss
    Socket states, socket options.
HTTP and HTTPS:
- HTTP Basics
  HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the World Wide Web. It is a set of rules for transferring text, images, sound, video, and other multimedia files between web browsers and servers.
  - Real life examples
    When you enter a URL in your browser to view a website, you're using HTTP. It's like requesting a specific book from a library.
  - Examples related to the topic
    HTTP is used for loading web pages, submitting forms, and interacting with various online services.
  - Want to know more?
    HTTP request methods (GET, POST), status codes (200 OK, 404 Not Found).
  - Later we'll discuss
    HTTP headers, cookies, and the evolution of HTTP versions.
- HTTPS for Secure Communication
  HTTPS (Hypertext Transfer Protocol Secure) is the secure version of HTTP. It adds a layer of encryption using SSL/TLS protocols, ensuring that data exchanged between the user's browser and the website's server is secure and cannot be easily intercepted.
  - Real life examples
    When you see a padlock icon in your browser's address bar, it indicates a secure HTTPS connection, similar to a sealed envelope for a private letter.
  - Examples related to the topic
    HTTPS is crucial for secure transactions like online banking, shopping, and protecting user login information.
  - Want to know more?
    SSL/TLS handshake process, obtaining and installing SSL certificates.
Network Security:
- Basics of network security, including concepts like firewalls and encryption:
  Network security involves protecting computer networks and the data they transmit from unauthorized access and threats. Firewalls are security devices that monitor and control incoming and outgoing network traffic, acting as a barrier between trusted and untrusted networks. Encryption is the process of converting data into a coded form that can only be accessed by authorized users, ensuring that sensitive information remains secure.
  - Real life examples
    Imagine a firewall as a security guard at the entrance of a building, checking who can enter and blocking unauthorized individuals.
    Encryption is like sending a secret message using a secret code that only the intended recipient can decode.
  - Examples related to the topic
    Firewalls prevent unauthorized access to a company's internal network from external sources, such as hackers or malicious software.
    Encryption is used when sending sensitive information, such as passwords or credit card details, over the internet to ensure that only the intended recipient can read it.
  - Want to know more? Google these points:
    How do firewalls work?
    Types of encryption algorithms.
    Best practices for network security.
  - Later we'll discuss:
    Intrusion detection systems.
    Virtual private networks (VPNs).
- Common Security Threats
  Security threats include viruses, malware, phishing attacks, and unauthorized access attempts. These threats can compromise the confidentiality, integrity, and availability of data.
  - Real life examples
    Just as you protect your home from burglars, network security defends against online threats seeking unauthorized access to your data.
  - Examples related to the topic
    Malware can be like a digital thief trying to steal sensitive information from your computer.
  - Want to know more?
    Types of malware (viruses, ransomware, spyware), social engineering attacks.
  - Later we'll discuss
    Advanced persistent threats, zero-day vulnerabilities.
Wireless Networking:
- Basics of wireless networking, including Wi-Fi standards and security considerations.
  Wireless networking enables devices to connect and communicate without physical cables. It utilizes radio waves to transmit data between devices, providing flexibility and convenience for users.
  - Real life examples
    Imagine a cordless phone; you can move around freely while staying connected. Wireless networking for devices like laptops and smartphones operates similarly.
  - Examples related to the topic
    Wi-Fi (Wireless Fidelity) is a common technology for wireless networking, allowing devices to connect to the internet without physical connections.
  - Want to know more?
    How wireless signals work, the difference between Wi-Fi and cellular networks.
  - Later we'll discuss
    Wireless communication protocols, emerging wireless technologies.

DIY

Try to ping some other IP address and see if there is a connection
```
ping 8.8.8.8
```

Creating a simple networked application using JavaScript and Node.js.

Install Node.JS using your terminal and google

Copy the code into a file named app.js.

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello, World!');
});

const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`Server is running on <http://localhost>:${PORT}`);
});

Open your terminal or command prompt.
Navigate to the directory containing app.js.
Run the following command
```
node app.js
```
Open this in your browser: http://localhost:3000

Experiment with Node.js, start by searching for the following:
- Node.js tutorials
- Node.js documentation
- Node.js example projects
- Node.js code samples

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Last updated 1 year ago

Basics of computer networks

Introduction to Networking:

Computers communicate with each other over a network by sending and receiving data.
- Local area networks (LANs) are used for communication within a small area, like an office, while wide area networks (WANs) cover larger geographical areas, like connecting offices in different cities.
Real life examples
- LAN: Computers in an office sharing files and printers.
- WAN: Connecting multiple branches of a company across different cities.
Examples related to the topic
- Sending an email from one computer to another.
- Streaming a video from a server to your device.
Want to know more? Google these points:
- How do LANs and WANs differ?
- How does data travel between computers on a network?
Later we'll discuss
- TCP/IP protocol suite
- IP addresses
Differentiating between local area networks (LANs) and wide area networks (WANs).

OSI Model:

The OSI model is a framework that defines how different devices communicate over a network. It consists of seven layers, each with its own specific functions. This model helps in understanding the flow of data between devices and enables interoperability between different network technologies.

OSI Model basics
- Real life examples
  - Imagine sending a letter to a friend. The process involves writing the letter (application layer), putting it in an envelope (transport layer), addressing the envelope (network layer), sending it through the postal system (data link layer), and finally delivering it to your friend (physical layer).
    Examples related to the topic
    When you visit a website, your web browser (application layer) sends a request to the server (transport layer) using the IP address (network layer). This process is known as the client-server communication model. The server then receives the request, which includes information about the specific page or resource you are trying to access. It processes the request by retrieving the necessary data or executing the required actions. Once the server has completed its processing, it generates a response, which includes the requested data or the result of the executed actions. The response is then sent back to your web browser through the same layers of the communication model. This process ensures that the information you requested is efficiently transmitted from the server to your browser, allowing you to view and interact with the website's content.

Understanding the purpose and functions of each OSI layer:
The OSI model is a framework that helps us understand how devices communicate over a network. It consists of seven layers, each with its own specific functions. Here's a brief description of each layer:
- Application Layer: This layer deals with user interaction and provides services for applications to access the network. It includes protocols like HTTP, FTP, and SMTP.
  - Real life examples
    Sending emails or browsing websites.
  - Examples related to the topic
    Using the HTTP protocol to request web pages.
- Presentation Layer: This layer is responsible for data formatting and encryption. It ensures that data from the application layer is correctly interpreted by the receiving device.
  - Real life examples
    Converting a file from one format to another
  - Examples related to the topic
    Encrypting data before sending it over the network.
- Session Layer: This layer establishes, manages, and terminates connections between devices. It allows devices to have conversations and ensures data integrity.
  - Real life examples
    Making a phone call or video conference.
  - Examples related to the topic
    Establishing a connection between two devices for data transfer.
- Transport Layer: This layer handles end-to-end communication and ensures reliable delivery of data. It breaks data into smaller packets and reassembles them at the destination.
  - Real life examples
    Sending a package through the mail.
  - Examples related to the topic
    Splitting a large file into smaller packets for transmission.
- Network Layer: This layer deals with network addressing and routing. It determines the best path for data packets to reach their destination.
  - Real life examples
    Using a GPS navigation system to find the most efficient route.
  - Examples related to the topic
    Using IP addresses to route data packets over the internet.
- Data Link Layer: This layer provides error-free transmission of data frames between devices on the same network. It also handles flow control and error detection.
  - Real life examples
    Sending a letter through the postal service.
  - Examples related to the topic
    Transmitting data frames between devices connected by Ethernet.
- Physical Layer: This layer deals with the physical transmission of data over the network. It includes specifications for cables, connectors, and other hardware.
  - Real life examples
    Speaking to someone face-to-face.
  - Examples related to the topic
    Transmitting electrical signals or light pulses through network cables.
- Want to know more? Google these points:
  - What are the functions of the OSI model layers?
  - How does data flow through the OSI model?
  - How does each layer of the OSI model work?
  - What are the advantages of using the OSI model for network communication?
- Later we'll discuss:
  - TCP/IP protocol suite
  - IP addresses

TCP/IP Stack:

Learning about the TCP/IP protocol suite, which is fundamental to the Internet.
The TCP/IP protocol suite is like a set of rules that computers follow to talk to each other on the internet.
- Real life examples
  - Imagine the TCP/IP suite as a recipe book for making a delicious dish. Each step (protocol) is essential to create the final meal (data transfer).
- Examples related to the topic
  - In this "recipe," TCP ensures the ingredients (data) are mixed properly, and IP is like the cooking instructions, making sure the dish (data) reaches its destination.
- Want to know more?
  - OSI Model, TCP vs. UDP, IP addressing.
- Later we'll discuss
  - Socket programming, network troubleshooting.
- Exploring the key protocols within TCP/IP, including TCP (Transmission Control Protocol) and IP (Internet Protocol).
  TCP and IP are like a dynamic duo - TCP ensures data arrives safely, and IP guides it to the right destination.
  - Real life examples
    Think of TCP as a trustworthy delivery person who checks the package (data) to make sure nothing is broken. IP is the address on the package, telling the delivery person where to go.
  - Examples related to the topic
    Before sending the package (data), TCP and IP have a quick chat (three-way handshake) to make sure everything is set for a smooth delivery.
    Initiation (SYN): The client sends a SYN packet to the server to start the connection.
    Acknowledgment and Agreement (SYN-ACK): The server responds with a SYN-ACK packet, acknowledging the client's request and signaling its willingness to establish a connection.
    Final Acknowledgment (ACK): Upon receiving the server's SYN-ACK, the client sends an ACK packet to confirm the connection is established.
    The three-way handshake is like a polite conversation before exchanging information. It ensures that both the client and server are aware of each other's presence, willing to communicate, and ready to start the data transfer. This process helps in preventing data loss and ensures a reliable and synchronized connection between the devices.
  - Want to know more?
    TCP flags, IPv4 vs. IPv6, subnetting.
    Packet loss, retransmission.

IP Addresses:

IP addresses are unique identifiers assigned to devices on a network. They allow devices to send and receive data to and from other devices. It's like a phone number for the internet.
- Real life examples
  - Each house having a unique address in a neighborhood.
- Examples related to the topic
  - Devices on a network having unique IP addresses to communicate with each other.
- Want to know more? Google these points:
  - How are IP addresses assigned?
  - What is the difference between IPv4 and IPv6?
- How are IP addresses assigned?
  IP addresses are assigned to devices on a network by network administrators or Internet Service Providers (ISPs). There are two main types of IP addresses: static and dynamic. Static IP addresses are manually assigned to devices and remain the same over time. Dynamic IP addresses are automatically assigned by the network's DHCP (Dynamic Host Configuration Protocol) server and can change periodically. IP addresses are essential for devices to communicate with each other on a network, similar to how each house has a unique address in a neighborhood.
  - Real life examples
    Regional postal services distributing address blocks to local post offices.
    Assigning a specific parking spot to each employee in an office building.
    Imagine going to a coffee shop and connecting your laptop to their Wi-Fi network. Instead of manually configuring your IP address, DHCP (Dynamic Host Configuration Protocol) automatically assigns one to your device.
  - Examples related to the topic
    Assigning a unique IP address to each device connected to a home Wi-Fi network.
    IP addresses are allocated globally by regional Internet registries (RIRs) who distribute them to Internet Service Providers (ISPs) or organizations within their region. This hierarchical system ensures efficient distribution of IP addresses worldwide.
  - Want to know more? Google these points:
    How does DHCP work?
    How are IP addresses allocated globally?
- Differentiating between IPv4 and IPv6 addressing:
  IPv4 and IPv6 are two different versions of the Internet Protocol, which is responsible for assigning unique addresses to devices on a network.
  - Real life examples
    Imagine a neighborhood where houses are assigned street addresses. IPv4 would be like using a 4-digit numbering system, which limits the number of unique addresses available. IPv6, on the other hand, would be like using a 6-digit numbering system, allowing for a much larger pool of unique addresses.
  - Examples related to the topic
    IPv4 addresses are structured as 32-bit, divided into four groups of numbers separated by periods. IPv6 addresses, on the other hand, are structured as 128-bit, divided into eight groups of hexadecimal numbers separated by colons.
    IPv4 addresses are represented in a dotted-decimal format, such as 192.168.0.1. IPv6 addresses are represented in a hexadecimal format, such as 2001:0db8:85a3:0000:0000:8a2e:0370:7334.
  - Want to know more? Google these points:
    What are the differences between IPv4 and IPv6?
    How are IPv4 and IPv6 addresses structured?
  - Later we'll discuss:
    TCP/IP protocol suite
    IP addresses

Subnetting:

Learning how to subnet IP addresses to efficiently allocate and manage network resources.
Subnetting is like dividing a big neighborhood (network) into smaller blocks for easier management. It helps in organizing and efficiently using IP addresses.
- Real life examples
  - Imagine a large field (network) being divided into smaller plots (subnets), each assigned to a different purpose.
  - Think of a subnet mask like a city map. A mask of 255.255.255.0 means you can move freely within a city block (subnet), but crossing streets (subnets) requires more effort.
- Examples related to the topic
  - Subnetting allows network administrators to allocate specific ranges of IP addresses to different departments or devices.
- Want to know more?
  - VLSM (Variable Length Subnet Masking), subnetting tools, subnet design best practices.
- Later we'll discuss
  - CIDR notation, subnetting in IPv6.
Subnet Masks
Subnet masks act like fences, separating the network and host portions of an IP address. Common subnet masks include 255.255.255.0 and 255.255.0.0.
- Real life examples
  - Think of a subnet mask like a city map. A mask of 255.255.255.0 means you can move freely within a city block (subnet), but crossing streets (subnets) requires more effort.
Public and Private IP Addresses
Public IP addresses are like street addresses that are visible to the outside world, while private IP addresses are like apartment numbers within a building, hidden from the public.
- Real life examples
  - Think of a public IP address as your home address, and private IP addresses as apartment numbers within your building. Another example is a small village that internally uses its own numbering system for houses, but most houses also have a public address.
  - Your home's public IP address is what allows your computer to connect to websites and servers on the internet.
- Examples related to the topic
  - Public IP addresses are used for devices that need to communicate with the internet, while private IP addresses are for devices within a local network.
  - Common private IP address ranges include 192.168.x.x, 172.16.x.x–172.31.x.x, and 10.x.x.x.
- Want to know more?
  - NAT (Network Address Translation), IP address allocation policies, IPv6 addressing
Other IP Addresses
Other IP addresses may refer to reserved or special-use addresses. These include loopback addresses, multicast addresses, and reserved ranges for documentation.
- Real life examples
  - The loopback address (127.0.0.1) is like talking to yourself in a conversation. It's used for testing network functionality on your own device.
- Want to know more?
  - Reserved IP address ranges, special-purpose addresses like APIPA (Automatic Private IP Addressing).
  - Multicast communication, the significance of loopback addresses in troubleshooting.

Routing:

Exploring the basics of routing and how routers facilitate communication between different networks:
Routing is the process of directing network traffic from one network to another. Routers are devices that help facilitate this communication by determining the best path for data to travel between networks. They use routing protocols to exchange information and build a map of the network. Routers analyze the destination IP address of incoming data packets and forward them to the appropriate network. They ensure that data reaches its intended destination by making decisions based on routing tables. Without routers, networks would not be able to connect with each other.
- Real life examples
  - Think of routing as planning a road trip. You use a map or GPS to find the best route to your destination, avoiding traffic and roadblocks.
- Examples related to the topic
  - When you access a website hosted on a server in a different country, routers help route your request through various networks to reach the server.
  - Routers play a crucial role in the internet, ensuring that data packets are directed to the correct networks worldwide.
  - Trick your computer into thinking that it is opening your own page instead of Google by adding an entry to the ‘hosts’ file like this: 127.0.0.1 google.com. This allows you to test web applications locally. However, please note that this change only affects your computer and does not affect other devices on the network or external routers when resolving .
- Want to know more? Google these points:
  - How do routers work?
  - Network topologies
  - Routing protocols
  - What are routing protocols?
  - What is the ‘hosts’ file?

DNS (Domain Name System):

Understanding the role of DNS in translating domain names to IP addresses.
DNS (Domain Name System) acts like a phone book for the internet, translating human-friendly domain names (like ) into computer-friendly IP addresses.
- Real life examples
  - Think of DNS like a librarian who helps you find a book (website) by translating its title (domain name) into the right section (IP address).
- Examples related to the topic
  - When you type a website's name, DNS quickly looks up the address, so you reach the correct online destination.
  - A common example is when you have issues opening certain pages on your computer, while others open without any problems. In such cases, try changing your DNS provider in the settings. Two common options are 8.8.8.8 and 8.8.4.4, both owned by Google.
- Want to know more?
  - DNS resolution process, recursive vs. authoritative DNS servers.
Exploring the hierarchical structure of the DNS.
The DNS is organized in a hierarchical structure, with different levels of authority. It starts with the root domain, followed by top-level domains (TLDs), and then individual domain names.
- Real life examples
  - Imagine a large organization with departments and teams. The root domain is like the CEO, TLDs are department heads, and individual domain names are team members.
- Examples related to the topic
  - The root domain is represented by a dot (.), and it leads to TLDs like .com, .org, and country-specific ones like .uk or .jp.
  - Some domains can be used only for some particular purposes like edu,
- Want to know more?
  - DNS zone files, authoritative name servers, DNS delegation.
  - Anycast DNS, the role of registrars in domain management.
Domain Registration Process
Owning a domain involves registering it through a domain registrar. You choose a unique domain name, check its availability, and pay a registration fee to the registrar for a specified period, usually annually.
Real-life examples
- Registering a domain is like reserving a unique business name with the government. Once registered, it's officially yours.
- Certain domain extensions, also known as TLDs, have specific purposes and restrictions. Examples include .edu for educational institutions, .gov for U.S. government entities, .mil for the U.S. Department of Defense, .int for international organizations, .museum for museums, .aero for the aerospace industry, and .coop for cooperative associations. These are some specialized domain extensions.
- Some domain extensions can only be reserved under certain circumstances. For example, the .ua extension can only be obtained if you have a trademark registered in Ukraine.

Ports and Sockets:

Learning about ports as communication endpoints in networking.
Ports are like doors on a computer. They allow different applications to send and receive data. Each port number is associated with a specific type of service or application.
- Real life examples
  - Think of ports as apartment numbers in a building. Each apartment (port) is a different residence (service) inside the building (computer).
- Examples related to the topic
  - Port 80 is commonly used for web traffic, like opening the front door for visitors to a website.
- Want to know more?
  - Well-known port numbers, dynamic vs. static ports.
- Later we'll discuss
  - Port forwarding, security considerations in port usage.
Port Numbers
Port numbers range from 0 to 65535. Well-known ports (0-1023) are reserved for standard services like HTTP (80) and FTP (21). Registered ports (1024-49151) are for user-registered services, and dynamic or private ports (49152-65535) are for temporary purposes.
- Real life examples
  - Think of port numbers like TV channels. Well-known channels (ports) are for common shows (services), while you can choose other channels (ports) for your personal preferences.
- Examples related to the topic
  - Port 443 is commonly used for secure web browsing (HTTPS). Port 80 is assigned to HTTP (Hypertext Transfer Protocol).
- Want to know more?
  - IANA's list of assigned port numbers.
- Later we'll discuss
  - Port scanning, port exhaustion.
Understanding sockets as a mechanism for processes on different devices to communicate.
Sockets are communication endpoints in a network. They enable processes on different devices to send and receive data. A socket consists of an IP address and a port number.
- Real life examples
  - Imagine a telephone as a socket. You have your phone number (IP address) and a specific extension (port) for communication.
- Examples related to the topic
  - A server socket might be waiting for calls (connections) on a specific phone line (port).
- Want to know more?
  - Types of sockets (stream vs. datagram), socket programming.
- Later we'll discuss
  - Socket states, socket options.

HTTP and HTTPS:

HTTP Basics
HTTP (Hypertext Transfer Protocol) is the foundation of data communication on the World Wide Web. It is a set of rules for transferring text, images, sound, video, and other multimedia files between web browsers and servers.
- Real life examples
  - When you enter a URL in your browser to view a website, you're using HTTP. It's like requesting a specific book from a library.
- Examples related to the topic
  - HTTP is used for loading web pages, submitting forms, and interacting with various online services.
- Want to know more?
  - HTTP request methods (GET, POST), status codes (200 OK, 404 Not Found).
- Later we'll discuss
  - HTTP headers, cookies, and the evolution of HTTP versions.
HTTPS for Secure Communication
HTTPS (Hypertext Transfer Protocol Secure) is the secure version of HTTP. It adds a layer of encryption using SSL/TLS protocols, ensuring that data exchanged between the user's browser and the website's server is secure and cannot be easily intercepted.
- Real life examples
  - When you see a padlock icon in your browser's address bar, it indicates a secure HTTPS connection, similar to a sealed envelope for a private letter.
- Examples related to the topic
  - HTTPS is crucial for secure transactions like online banking, shopping, and protecting user login information.
- Want to know more?
  - SSL/TLS handshake process, obtaining and installing SSL certificates.

Network Security:

Basics of network security, including concepts like firewalls and encryption:
Network security involves protecting computer networks and the data they transmit from unauthorized access and threats. Firewalls are security devices that monitor and control incoming and outgoing network traffic, acting as a barrier between trusted and untrusted networks. Encryption is the process of converting data into a coded form that can only be accessed by authorized users, ensuring that sensitive information remains secure.
- Real life examples
  - Imagine a firewall as a security guard at the entrance of a building, checking who can enter and blocking unauthorized individuals.
  - Encryption is like sending a secret message using a secret code that only the intended recipient can decode.
- Examples related to the topic
  - Firewalls prevent unauthorized access to a company's internal network from external sources, such as hackers or malicious software.
  - Encryption is used when sending sensitive information, such as passwords or credit card details, over the internet to ensure that only the intended recipient can read it.
- Want to know more? Google these points:
  - How do firewalls work?
  - Types of encryption algorithms.
  - Best practices for network security.
- Later we'll discuss:
  - Intrusion detection systems.
  - Virtual private networks (VPNs).
Common Security Threats
Security threats include viruses, malware, phishing attacks, and unauthorized access attempts. These threats can compromise the confidentiality, integrity, and availability of data.
- Real life examples
  - Just as you protect your home from burglars, network security defends against online threats seeking unauthorized access to your data.
- Examples related to the topic
  - Malware can be like a digital thief trying to steal sensitive information from your computer.
- Want to know more?
  - Types of malware (viruses, ransomware, spyware), social engineering attacks.
- Later we'll discuss
  - Advanced persistent threats, zero-day vulnerabilities.

Wireless Networking:

Basics of wireless networking, including Wi-Fi standards and security considerations.
Wireless networking enables devices to connect and communicate without physical cables. It utilizes radio waves to transmit data between devices, providing flexibility and convenience for users.
- Real life examples
  - Imagine a cordless phone; you can move around freely while staying connected. Wireless networking for devices like laptops and smartphones operates similarly.
- Examples related to the topic
  - Wi-Fi (Wireless Fidelity) is a common technology for wireless networking, allowing devices to connect to the internet without physical connections.
- Want to know more?
  - How wireless signals work, the difference between Wi-Fi and cellular networks.
- Later we'll discuss
  - Wireless communication protocols, emerging wireless technologies.

DIY

Try to ping some other IP address and see if there is a connection

ping 8.8.8.8

Creating a simple networked application using JavaScript and Node.js.

Install Node.JS using your terminal and google

Copy the code into a file named app.js.

const http = require('http');

const server = http.createServer((req, res) => {
  res.writeHead(200, { 'Content-Type': 'text/plain' });
  res.end('Hello, World!');
});

const PORT = process.env.PORT || 3000;
server.listen(PORT, () => {
  console.log(`Server is running on <http://localhost>:${PORT}`);
});