Transcript for:
Basics of Networking and Security Concepts

welcome everyone to this simplified animated networking course this course is designed for anyone struggling to understand networking Concepts or looking to get started with computer networks I guarantee that by the end of this course you will have a solid foundation in computer networking with clear practical Concepts this course uses simple explanations combined with proper animations to explain Network ning Concepts now apart from all the essential topics in networking I have also covered the binary number system which is a bit Advanced but equally important beginners often struggle with binary number system but I have simplified it in a way that everyone will be able to understand it without any problem my suggestion for you especially if you are a complete beginner is to avoid skipping any part of the video and learn sequentially this way you will be able to connect the dots and build a solid foundation as you progress through the course this course is divided into two sections in the first half of the course we will cover all the essential networking Concepts that form the foundation of networking including important terms such as these then we will move on to the essential network devices used for creating a network moving forward we will learn the most important topic the OSI model in detail which is the heart of computer networking along with many other topics in the second half we will dive into advanced concepts that are particularly important for cyber security and ethical hacking we will learn the essential cryptography and binary number system if you want to learn more about networking and start your career in cyber security you can check out my udmi course we will start by understanding the very Basics what a computer network is why computer networks are needed and what is resource sharing with real world examples don't worry about cables and devices used in creating a network we will cover those details in upcoming sections a computer network is essentially a group of interconnected computers or devices when two or more devices connect to each other they collectively form a computer network the connection can be wired like this or wiress now why do devices need to be interconnected because data can only be exchanged if devices are connected to each other so when devices connect they form a computer network once connected they can start sending data to each other that's why computer networks are required because it enables devices to send data to each other this is the simplest possible computer network later in the course we will learn about more complex and sophisticated networks being used today computer networks were developed in the early 1960s and back then only computers were part of a network however Computing has evolved significantly today a computer network is not limited to interconnected computers devices such as mobile phones servers tablets switches routers printers smart watches and other smart devices are all integral components of a computer network now let's address the real questions why are computer networks needed and what is resource sharing as we have already discussed devices can only exchange data when they are connected to each other this forms a computer network enabling data communication apart from data communication a computer network offers resource sharing which is the most important feature or component of a computer network let's understand resource sharing with with a few real world examples a network can be either wired or Wireless in a wireless network devices connect to the network using Wi-Fi right when you connect to a Wi-Fi network you and all other devices connected to that Network can access the internet right this is an example of resource sharing where multiple devices connected to the same Wi-Fi net Network share or utilize the internet connection provided by the Wi-Fi network similarly a computer network allows us to share devices like printers scanners servers file servers Etc printers are essential devices in most offices right now without a network each person or device would need their own printer or they would all have to connect directly to the same printer this is inconvenient costly and inefficient right now a network solves this problem by allowing devices on the network to share the printer all we have to do is connect the printer to the network once you connect a printer to the network then all the devices connected to the network can share or use the printer they don't have to directly connect to the printer each device can use the printer whenever they need it this is called the resource sharing that a network provides here I am showing you the printer being connected to a switch using a wire or ethernet cable however printers can also connect to a wireless network or router nowadays printers have wireless capabilities as well data sharing or file sharing is another common activity in offices and even in home networks we can set up a file server where files can be stored and connect it to the network then everyone connected to the network can access the files otherwise files would have to be sent to everyone individually which can be time consuming so guys to summarize a computer network allows devices to communicate with each other and share resources with other devices on the network this saves money and makes it easier for people to work together you will gain Clarity on networks in the upcoming videos and sections now let's discuss types of networks computer networks are divided into different types based on their size and the geographic area that they cover some some of the most common types of computer networks include Lan man when w Lan and personal area networks in computer networking the term packet is used all the time when dealing with data a packet is a small segment of a larger file when two devices exchange data over a computer network such as the internet the data or file is first divided into smaller pieces or segments called packets the packets are then transmitted to the receiver let's understand packets with an example for better Clarity let's say device a wants to send a file to another device be over the internet now the file is not sent all at once before sending the file it is divided into multiple smaller parts or SE Ms and these segments are technically called packets in computer networking then each packet is sent independently to its destination at the destination the packets are reassembled in the correct order to form the original file so a packet is just a piece of a larger file and data is sent in a series of packets every web page email image video or audio file that you send or download is transmitted in a series of different packets at the destination the packets are reassembled to form the original file now why are files sent in this manner rather than all at once breaking a file into smaller packets improves data reliability let's say that if a packet is lost or corrupted during transmission then only that specific packet needs to be resent on the other hand if you send a complete file all at once and it gets corrupted or lost in transit the sender will need to resend the entire file this would result in the waste of your bandwidth and network resources packets also improve efficiency dividing files into smaller packets allows each packet to take a different route to reach the destination the maximum amount of data that a packet can carry depends on various factors such as the Network Technology being used and the specific protocol in use the standard is currently 15500 bytes the maximum size of data that can be sent in a single packet is 1500 bytes there is a newer technology called jumbo frames a jumbo frame can carry a maximum of 9,000 bytes we will discuss this further in the OSI model section in detail thank you very much guys IP address stands for Internet Protocol and it is a unique number assigned to every device connected to a network or the inter EET when you connect to a Wi-Fi network or a wired ethernet Network your device is automatically assigned an IP address now why is an IP address needed an IP address identifies each individual device on the internet an IP address helps locate devices on the internet IP addresses ensure that data reaches the correct destination just like individuals or businesses use a home or office address for sending and receiving mail devices on the internet also needs a digital address for sending and receiving data let's say that you want to send an email or any type of data to someone in a different country or location to deliver the data the sender needs to know the location or address of the receiver then the sender will be able to deliver the data to that address or IP address so this is what an IP address does it essentially helps locate the device on the internet therefore each device on the internet must have an IP address if it wants to access the internet or communicate with other devices on the internet a device can send data to any other device anywhere in the world based on the IP address remember that computers communicate with each other using IP addresses on the internet without IP addresses devices can't exchange data over the Internet each packet contains two IP addresses the IP address of the sender who is sending the packet and the IP address of the receiver where the packet will be delivered there are two versions of IP addresses ipv4 and IPv6 ipv4 is the most commonly used IP address now let me practically show you how to view your own IP address press Windows key type CMD now click on command prompt and here type the command ip config SL all press enter and under the wireless land adapter Wi-Fi locate the field that says ipv4 address here it is as you can see this is my own ipv4 address and this is the IPv6 address this is the IPv6 address and if you are connected to your network using an ethernet cable then you will find all these Network details under the ethernet section let me scroll up here it is ethernet adap ethernet so if you are connected to your network using an ethernet cable then you will find the network details under this interface ethernet adapter host is one of the most commonly used terms in computer networking so it is important to understand it at the beginning of the course in networking a host is any device that can communicate with other devices on a network this means that any device that can send or receive data is called a host such as computers laptops smartphones tablets servers ATC now we have new additions to hosts in modern days these additions include smart devices such as smart watches smart refrigerators gaming consoles Smart TVs Etc these smart devices are capable of communicating or sending and receiving data each host or device capable of interacting with other devices has a unique IP address this IP address enables seamless communication between devices on the internet whether you are a network administrator or have any role managing a network dealing with servers will be a common task so what exactly is a server first of all a server is also a computer the name server might sound very intimidating but it is essentially just another computer so what makes a server different from a regular computer the only difference between a regular computer and a server is that a server is configured to provide or serve specific services to users the term server denotes a computer or program designed to serve or provide services to users or other computers what a server serves depends on what you want it to serve we have different types of servers for example a web server serves websites to users in simple terms a web server provides access to websites when you type let's say cyber security on Google it returns results related to your search query right now it is the web server that processes your request your search query is received by Google's web server which then processes it and sends back search results to your web browser as I mentioned earlier a server is essentially just a computer so how did Google turn a regular computer into a web server that answers your questions to turn a regular computer into a web server we need to install and configure certain things first we need to install software called a web server there are two popular free web servers called Apache and inex but Google uses its own server called Google web server which processes your queries apart from installing a web server we have to configure other aspects such as do main name port forwarding ATC to make a website accessible to everyone by following these steps you can effectively transform any regular system into a fully functional web server there are many types of servers such as web servers mail servers file servers database servers DNS servers ATC a web server delivers websites to users a file server facilitates file sharing and a mail server handles email communication when you send or receive an email it is the mail server that makes this process possible Gmail is the most popular email service offered by Google and it runs on its own dedicated mail servers typically we use dedicated servers for each service to summarize servers whenever you install a service on a computer that serves multiple users that computer becomes a server keep in mind that the servers need to be reliable robust and Powerful because the server typically needs to be up and running 24/7 let's say if Google's web server goes down you will not be able to use Google if Google's server goes offline even for a few minutes it could cost them billions servers are usually accessible to many people and can be used for a variety of purposes so let's start with the ethernet cable we can connect to a network in two ways either through a wired connection or wirelessly right we connect to a wireless network using Wi-Fi to access the internet and other network resources and if you want to connect to a wired Network you need a wire now the wire or cable that makes this possible is called an ethernet cable an ethernet cable connects computers to a wired Network wired network is also known as an Ethernet Network the ethernet cable is also known as the network cable here is what an ethernet cable looks like the ethernet cable has a connector on each end these are called rg45 connectors to connect a device to a wired Network we need to connect one end of the ethernet cable to a computer and other end to a device such as a switch or router once connected you will be successfully connected to the network and can access the internet or other network resources ethernet cables not only connects computers to a wired Network they can also be used to connect other devices like printers servers or any other device that supports it this is just an overview of ethernet cables we'll get back to it in a dedicated section now let's move on to the Lan ports each system has one landan port this is what a landan port looks like to find the L port on your device look for a small rectangular P that looks like this now when you connect an Ethernet cable to a device this is where the ethernet cable gets plugged in the RJ45 connector of the ethernet cable gets plugged into the landan port of a system a landport is also known as the network port or ethernet port routers switches computers even printers have the LPS you can also directly connect to computers using an ethernet cable because it has connectors on both ends connect one end to one device and other end to the other device and you will be connected once connected both devices can exchange data so what is a MAC address a MAC address is a 12 digit hexadecimal number this is what a typical Mac address looks like later I will show you the actual Mac address practically Mac stands for media access control it is also known as the physical address or Hardware address a MAC address is assigned to a network interface card a MAC address uniquely identifies a computer the MAC address is embedded or burned inside the network interface card each network interface card whether Wireless wired or external has a unique Mac address embedded in it a MAC address is permanent and can't be changed Mac address is divided into two parts the first six digits identify the manufacturer that developed the Nic and the remaining six digits identify the device itself now let's address the actual question why is a MAC address needed the MAC address is essential for data communication if one device wants to send data to another device it needs the MAC address of the receiver in order for devices to exchange data on the same network or across different networks they need Mac addresses of each other to exchange data between them here we have an obvious question we also have IP addresses right what is the role of an IP address then since the MAC address sounds similar to an IP address well both Mac address and IP address work together to deliver data to the destination device remember an IP address is not permanent it keeps changing your ISP typically assigns a new IP IP address to your network or mobile phone automatically after a certain period of time when you move to a new location or country the internet service provider of that area also assigns you a new IP address therefore we require a system that can pinpoint a devices location and this is accomplished by the IP address the main purpose of an IP address is to to locate your current location on the other hand a MAC address is permanent and can't be changed therefore we need both to communicate with other devices the IP address is used to locate the devices current location after locating the device the MAC address or physical address is used to deliver data to the actual physical device let's say there were no IP addresses in this case other devices or networks would assume that you are in the same location or network even if you change your location or network because Mac addresses are fixed therefore we need IP addresses to differentiate devices based on their location and an IP address gets updated based on your location when you move to a new location the ISP or Internet service provider of that area automatically assigns a new IP address to your device IP addresses are essential for sending data to devices in different networks or locations an IP address locates the device and the MAC address is used to deliver data to the physical device devices on the same Network can communicate directly using their Mac addresses we don't need IP addresses to communicate in the same network now let me practically demonstrate how to view your own Mac address press Windows key type CMD click on command prompt and here type ip config forward slash all press enter and under the wireless LAN adapter Wi-Fi locate the field that says physical address here it is physical address this is how a MAC address looks like this is my own Mac address for my wireless LAN adapter as we have already discussed the MAC address is also known as the physical address now each network interface card has a unique Mac address so this is the MAC address for my wireless LAN adapter and let me find the MAC address for my ethernet card let me scroll up here it is as you can see this is my wired ethernet adapter and this is the physical address or Mac address for my ethernet adapter to understand hubs let's first discuss why hubs and similar devices are needed this will provide the necessary context to understand hubs and switches is suppose computer a wants to send data to B to send data first we need to connect these two computers directly with an ethernet cable or by using a wireless connection once you connect them it technically is a computer network when two or more devices are connected to each other it is called a computer network now both connected devices can send data to each other obviously it is the simplest possible Network this method of connecting devices directly to each other works well for two devices however if we add a third computer we then need to connect it to both of the other computers for them to communicate with each other if we continue adding more computers we must connect each new computer to all of the existing computers as the number number of computers increases connecting them all directly becomes increasingly difficult and inefficient so wiring gets overwhelming now hubs were developed to solve this exact problem a hub was developed to simplify network connectivity a hub simplifies how devices connect to each other and communicate efficiently with minimal wiring a hub is a central multiport device device with multiple ports where various devices can connect to connect a system to the hub an ethernet cable is required an ethernet cable has connectors at both ends called rg45 connectors right to connect your computer or any device to a hub connect one end of an ethernet cable to the system and other end to the hub's landport similarly other devices can connect to the hub using ethernet cables once you connect your system to ahub you can communicate with all the devices that are connected to the hub now your computer is part of this Lan Network a lan Network can be created using a hub when multiple devices connect to a hub they collectively form a computer network this is a lan Network these connected devices can send data to each other other through the Hub The Hub manages communication between all the connected devices now let's understand how a hub facilitates communication between devices the way a hub works is that when it receives a packet it sends that packet to all the devices connected to it let's say that a wants to send data to C the packet first goes to the The Hub and the Hub broadcasts or sends the packet to all devices connected to it including the destination device C The Hub basically copies the packet to all its ports however by default all other devices reject or discard the packet except for the intended device C only the destination device C accepts the packet each packet contains the Mac addresses of the sender and receiver when the packet arrives at device C it checks the destination Mac address in the packet to see if it matches its own Mac address if the Mac addresses match then device C accepts the packet because it is intended for it so that's how a hub Works each packet that arrives at the The Hub is sent to all the connected devices however only the device for which the packet is intended accepts It While others reject it similarly all other devices connected to the hub can send data to any device that is connected to it the communication flow Remains the Same the packet that one system sends to a specific system connected to the Hub is sent to all other devices connected to it this is a drawback of a hub we will discuss it in the next video so guys that's how a hub simplifies connectivity you only need an ethernet cable to connect to the network or Hub and then you can communicate with all other devices connected to it without having to connect to them directly a switch is essentially an improved version of a hub it is an advanced networking device that addresses the limitations of hubs it offers significant improvements in network performance security and efficiency a hub has two major flaws it lacks intelligence and is insecure when a hub receives a packet it forwards it to all connected devices even if the packet is not intended for them leading to unnecessary data exposure and potential security risks this creates a security concern because by default devices connected to a hub only accept or receive the packet that are sent to them however a computer or network card can be configured to accept packets that are not sent to it now this modification makes the network less secure because devices can potentially receive and process data packets that are not sent to them and they could potentially intercept and steal sensitive data being exchanged between other devices another drawback of a hub is that it generates unnecessary Network traffic because instead of sending packets directly to the intended receiver a hub sends all packets to all connected devices this can lead to bandwidth congestion and slow down the network for all users now the switch basically addresses these two problems or limitations of a hub the switch is similar to a hub this is how a switch looks like a switch is also a multi-port central device with many Lan ports the total number of ports in a switch depends on the size and type of switch most switches have a minimum of five Lan ports and there are switches with 12 24 and 48 ports as well the switch allows computers or other devices to connect to a network through an Ethernet cable so that they can communicate with each other and access the internet and network resources the process of connecting a device to a switch which is the same as we discussed in the previous video we have to connect one end of the ethernet cable to the computer and other end of the ethernet cable to the switcher we can connect computers servers or printers to a switch using an ethernet cable which allows them to communicate with each other once you connect devices to a switch it creates a lan or local area network a simple lan can be created using a switch by connecting devices to it unlike a hub a switch is a smart device the way a switch works is that it stores the MAC address of each device connected to it a switch basically learns which device is connected to which Port by maintaining a MAC address table the MAC address Table stores the MAC address of each device connected to the switch and the port number on which the device is connected for example if device a connects to Port one on the switch the switch stores its Mac address in its Mac address table along with the port number to which it is connected this is how the entry looks like in the table this means that computer a is connected to port number one this will which does this for every device that connects to it it stores the MAC address of each device and the port number to which they are connected and how a switch exactly acquires the Mac addresses will be covered in a separate video now let's see how a switch works and forwards data let's say device a wants to send data to C the packet first goes to the switch every packet contains two Mac addresses the MAC address of the sender and the MAC address of the receiver or destination where the packet needs to be delivered now the switch checks the destination Mac address in the packet and matches it against the addresses in the MAC address table if the destination Mac address is found in the table then the switch forward towards the packet to the port number associated with that Mac address in this case the destination Mac address is at Port number three so the switch forwards the packet to the device C so unlike a hub it sends packets only to the intended device similarly if any device connected to the switch wants to communicate with another device the same process is followed the pack goes to the switch the switch checks the MAC address table and forwards the packet to the destination a switch is capable of reading Mac addresses whereas The Hub can't read Mac addresses that's why it forwards packets to everyone so guys that's how a switch works the data is delivered or forwarded only to the intended device making it secure a switch is among the most commonly used devices today in wir network a switch is always the preferred device We are continuing where we left off in the previous video in this video we will discuss routers routers are extremely important now to understand routers let's first review the central devices we have already covered such as hubs and switches this will help us understand routers more clearly and provide the context for understanding routers and their requirements a hub or switch allows devices to communicate with each other within the same network or local area network right the devices connected to a switch can communicate with each other easily now let's say that device a wants to access Google or the internet however Google server is not available within the network or Lan it is located somewhere on the internet therefore to access google.com or the internet computer a and all other devices in the network must leave their own network to reach or access Google a switch can't route or send data outside of the network it is designed to facilitate communication only within the same network or Lan so we need a device that can route or send data packets outside of the local area network that device is router a router allows devices on Lan networks to communicate with external networks such as the internet this is how a router looks like so to access the internet we must connect the switch to a router and the ethernet cable is used for this connection just connect one end of the ethernet cable to any Lan Port of the switch and other end of the cable to the Lan port on the router a router has at least one Lan Port once the switch is connected to the router Router will connect your network to the internet now devices connected to the switch or network can access the internet now when any device on the Lan Network needs to access anything on the internet the switch forwards packets to the router and the router sends the packets to the destination a switch understands Mac addresses which means it forwards packets based on the destination MAC address on the other hand a router understands IP addresses a router forwards packets based on the destination IP address in the packet now let's understand the the complete communication flow with an example let's say device a wants to access Google the packet first goes to the switch and then the switch forwards the packet to the router as mentioned earlier routers work with IP addresses the router checks the destination IP address in the packet in my case the packet contains IP address of Google and based on this destination IP address the router forwards the packet to the Google and the reply that Google sends back to device a will follow the reverse path like this packet arrives at the router which forwards it to the switch and the switch forwards it to the destination device a similarly if any other device connected to the switch or wirelessly wants to access the internet communication process Remains the Same remember that most routers also have a builtin switch you can directly connect computers to a router using an ethernet cable however a router typically doesn't have many Lan ports so a dedicated switch is typically used for Wired connectivity and provides connections to more devices so if you are directly connecting to the router it means the router has a buil-in switch another very important function of a router is to select the path that packets need to take to reach their destination and then forward them the internet is essentially a huge collection of interconnected networks or Lan networks this means that different networks communicate with each other to forward data to the correct destination the networks communicate with each other through routers routers connect the networks therefore each Network must have a router if it wants to access the internet since the internet is a web of interconnected routers data must go through these routers to reach its destination the job of a router is is to select the best available path that packets need to go through to reach their destination this is called routing routing is the process of selecting the path that data must go through to reach its destination there are two main types of routers wireless routers and wired routers a wireless router allows devices to connect to a network wireless LLY using Wi-Fi a wireless router is used to create a w Lan Wireless local area network on the other hand a wired router allows devices to connect to the router using a wire or an ethernet cable these routers are mostly used in home networks and small offices keep in mind that a wireless router typically supports both wired and wireless connectivity a wireless router may or may not have multiple Lan ports however each wireless router has at least one landport so far we have learned about fundamental network devices like switches routers and ethernet cables now the only missing mandatory component needed to create a functioning network is a modem so in this video we will learn what a modem is how it works and the difference between a modem and a router so let's first understand what a modem is and why it is needed the modem in simplest terms brings the internet to your home or office it essentially connects your Lan Network to the internet suppose you decide to set up a broadband internet connection at your home or office in this case you will first need to contact your local internet service provider and purchase a broadband connection from them to provide internet access to your location your ISP will use a cable or wire to connect your home to the isp's network to deliver the internet a modem essentially maintains a dedicated physical connection from your home or office to your internet service provider the cable provided by your ISP is plugged into the modem now modem needs to be connected to the router the cable used for connecting the modem to the router is an ethernet cable connect one end of the ethernet cable to the Lan port on the modem and the other end to the van port on the router I am repeating again connect the other end of the ethernet cable to the one port on the router there are are two types of ports on routers Lan and when the van Port essentially connects your network to the internet you might also see internet instead of Vanport they are both the same thing once you connect your router to the modem using the Vanport you will be able to access the internet most routers have several land boards typically around three you can connect your computers to these ports and access the internet if you need more ethernet ports for Wired devices you can connect a switch to your router as we discussed in the previous video routers can be either Wireless or wired if your router is wireless devices on your network can access the internet using Wi-Fi now you have a functioning Network now let's discuss some of the technical details and main functions of a modem a modem converts analog signals to digital signals and digital signals to analog signals this conversion is absolutely necessary because the wires or physical cable infrastructure that brings the internet to homes and offices use analog signals the data is transmitted in analog form through the wires however computers and other digital devices only understand binary language or digital signals zeros and ones so we need a device that can convert analog signals to digital signals and vice versa the modem is that device modem stands for modulator demodulator modulation is the process of converting digital signals to analog signals and demodulation is the process of converting analog signals back to digital signals when the analog signals arrive at the modem it converts them back to digital signals so that computers and other digital devices can understand or read them the modem can be a dedicated device but now they are often built into routers these days a router has a builtin modem this means that you can have a router that also functions as a modem however there are still some cases where you might need a dedicated modem such as if you have a very high-speed internet connection or a complex Network set up now the modem seems to be very similar to the router right however there is a difference a modem is a device that connects your home or off office to your internet service provider through a physical connection or wire it brings the internet physically to your place on the other hand a router allows devices connected to the network to access the internet as we discussed in the previous video routers also decide the path that packets must pass through to reach the destination we are going to wrap up this section with wireless access point points it is another important device used in computer networks so in this video we will learn about the wireless access point and the difference between a wireless access point and a router sometimes people mistake both devices for being the same a wireless access point is also known as a wireless AP this is what a wireless access point typically looks like it typically has external antennas however some access points have built in antennas as well now before we discuss the wireless access point in detail let's talk about routers briefly then we will be able to understand why wireless access point was developed there are two types of routers wireless routers and wired routers a wireless router supports wireless connections allowing different devices to connect to the network wirelessly using Wi-Fi on the other hand the wired router does not support wireless connectivity you can't connect to a wired Network or router using Wi-Fi we have to use the ethernet cable to connect to a wired router now let's say that you have a wired router that does not support wireless connectivity and you want to enable wireless connectivity so that devices can connect to the network wirelessly using Wi-Fi this is where the wireless access point comes into to solve the issue a wireless access point is a network device that allows devices to connect to a network using Wi-Fi or wirelessly now to enable wireless connectivity we need an ethernet cable simply connect one end of an ethernet cable to the wireless access point and the other end to the wired router the wireless access point can also be connected to a switch as well now it will start transmitting the radio waves now devices such as computers mobile phones or tablets can connect to the network wirelessly using Wi-Fi so an access point is a device that allows wireless devices to connect to a wired Network a wireless access point can also be used to extend the range of a wireless network wireless access points are frequently used in homes businesses and other public places to extend the reach of a Wi-Fi network and offer improved coverage let's say if you have a large office with multiple blocks and many people a wireless router has limited range and it can't provide connectivity to everyone in the large block this is where we can use the wireless access point you can add one or more wireless access points to extend the Wi-Fi signal to all areas of your office or home to do this you simply need to connect the wireless access point to the main router using an ethernet cable once the access point is connected to the main router it will provide access to the wireless network now devices from all Corners can access the network using their Wi-Fi all the devices are connected to a single network using different access points this entire network is managed by the main router if any device on the network wants to access the internet the packets have to go through the main router everything is managed by by a single router wireless access points are well suited for such setups or large offices because they are easy to manage alternatively you can also use wireless routers instead of wireless access points to provide Wireless connectivity to everyone by placing individual wireless routers instead of wireless access points however this can create manageability problems for example example if you use wireless routers instead of wireless access points you will need to configure each router individually if you want to make changes to the network however with wireless access points you can manage the entire network using a single router this is because wireless access points are typically connected to a central router which allows you to configure all the aps from a single location or device now let's talk about difference between a wireless router and wireless access point wireless routers and wireless access points are two different devices with distinct capabilities a wireless router can support both wired and wireless connections typically a router has multiple features such as a built-in switch firewall DHCP server Etc a router supports all these features on the other hand the sole purpose of a wireless access point is to provide Wireless connectivity and extend the network coverage it only transmits radio waves so that devices can connect to the network wirelessly that's all you need to know about the wireless access point The OSI model is one of the most important topics in computer networking the OSI model is the foundation for understanding Network architecture all right so what is the OSI model OSI stands for open systems interconnection in simple terms if you want to understand how two devices sitting in different countries or on the same network are able to communicate and send data to each other then the OSI model is your answer the OSI model basically explains each component involved in sending and delivering data from one computer to another over the Internet such as how data is prepared before it leaves the senders computer how it travels through various paths or networks to reach the destination and finally how data is processed and received by the destination device or receiver sending data from one device to another over the Internet is a very complex process that involves many steps let's say you want to send a file to someone who is sitting in another country or network your system has to figure out where to exactly send the data how to send it and make sure that the data is delivered to the receiver without any errors Etc so the OSI model helps us to understand all of these steps involved in the process of sending and receiving data over internet in detail that's why OSI is essential in computer networking as a network administrator or cyber security engineer learning the data communication process is the most fundamental thing the OSI model is a seven layer model transmitting data over the Internet is a complex task to simplify this problem OSI divided all the functions into seven smaller parts in technical terms these parts are called layers OSI layers each layer of The OSI model is assigned specific tasks or responsibilities the reason for splitting the OSI model into seven layers is simple it makes it easier to detect and solve problems separately this layered approach can easily tell us in which part the error or problem is all seven layers work together to transmit data from one device to another across the globe The OSI model is very useful for troubleshooting network problems Network Engineers always use the OSI model to detect and troubleshoot network problems once you understand the function of each layer it helps us pinpoint errors to specific layers using OSI we can narrow down and isolate the errors or possible causes of the errors to a specific layer and resolve it more quickly and easily the layered approach works best for troubleshooting the first layer in the OSI stack is the application layer the layers in OSI are numbered from bottom to up the application layer is the seventh and the first layer from the top now the application layer is closest to us the end users application layer allows us to access or use different network services such as sending emails making video and audio calls transferring files browsing websites Etc we access or use these Network Services using various Network applications Network applications are those that depend on the internet for communication such as Zoom for video calls web browsers like Chrome or Firefox for browsing websites outlook for emails and and FTP clients for file transfers ATC all of these are network applications now to be very clear Network applications are not part of the application layer they don't reside within the application layer Network applications depend on the application layer to function properly the job of the application layer is to provide the protocols that various Network applications need need to function correctly the application layer communicates or interacts with network applications through its protocols each layer of the OSI model has its own set of protocols the application layer has many protocols such as HTTP https tnet sip SSH FTP Etc Network applications depend on these protocols to function correctly let's understand this with a few examples when you browse a website it is the HTTP protocol that makes the web surfing possible allowing you to view websites at the beginning of each URL you will see either https or HTTP right all web applications depend on the HTTP or https protocol to function properly https is essentially the secure version of HTTP that's why you see https at the beginning of most website URLs both Protocols are part of the application layer when you visit a website your network application such as fir foox interacts with application layer using the HTTP protocol if you send or receive an email it is done using the SMTP protocol SMTP protocol manages emails file transfer is done through FTP protocol video calling applications like Zoom or Discord use the Sip protocol along with other protocols SMTP sip SSH and FTP all these Protocols are part of the application layer therefore all Network applications or Services rely on application layer protocols to function correctly so to summarize the application layer provides the required interface and protocols for Network applications to function each layer of the OSI model coordinates with specific devices The OSI model is all about explaining data communication process and in computer networking it is the actual physical devices that make data communication possible Right therefore each layer of the OSI model coordinates with specific devices and the application layer devices are those that we use to access network applications or generate data such as personal computers mobile phones laptops tablets Etc we run networking applications on these devices to access websites make calls and transfer files Etc so these devices operate at the application layer servers are also application layer devices the data or protocol data unit at the application layer is simply called data we will learn more about it in later video the presentation layer receives data from the application layer the presentation layer performs four main tasks translation encryption decryption and compression let's discuss them one by one starting with translation the presentation layer receiv receives data from the application layer in its raw form it can be characters numbers images or any other data generated by users through Network applications therefore it translates or converts the data into a format that a machine can understand which is binary ones and zeros the raw data gets converted or translated into binary presentation layer is is also responsible for translating data into a syntax or format that the application layer of the receiving device can understand the two devices that are communicating might use different encoding methods encoding in computers is the process of converting data such as text images audio or any Digital Data into a format that can be stored or transmitted electronically for example when you press let's say the key A on your keyboard a is converted into a binary code using an encoding scheme like Sky the data can only be stored or transmitted after it is encoded this binary code is then stored in the computer's memory or transmitted over a network similarly all types of data such as audio video and images are converted into binary encoding is a separate topic that will be covered in a dedicated section there are different encoding schemes such as SK and ebcd let's say the sender uses the SK scheme for encoding data and the receiver is using the ebcdic method or scheme then the presentation layer converts s key to ebcd I so that the receiving device can understand the data and display accurately without converting one format to another data will not be displayed or represented accurately by the receiver encoding is a v topic beyond the scope of this video or section just understand that if needed the presentation layer can convert one encoding scheme to another this is called translation in the presentation layer another important responsibility of the presentation layer is encryption and decryption when two devices are communicating over an encrypted connection the presentation layer handles encryption and decryption encryption is used to protect your data from cyber criminals https websites are example of encryption when you visit an https website your data is encrypted before it leaves your system encryption is simply the process of making data unreadable before sending it to the destination now if a hacker or cyber criminal intercepts the data or your communication they can't see what you are sending or receiving they will only see the encrypted text only the receiver can see the original data because the data is decrypted back to its original form only at the receiver's device only the receiver can decrypt the data all the big applications and websites use encryption to protect your data like I mentioned earlier in the application layer each layer has its own set of of protocols that manage different things in the presentation layer we have the TLs protocol which is responsible for encrypting and decrypting data so encryption decryption and data security are handled by the presentation layer the presentation layer is also responsible for data compression which is a method used to reduce file size it achieves this by reducing the number of bits that represent the original data it uses compression algorithms or techniques to reduce the size of files so they can be transmitted more quickly compressing data does not impact the file itself it merely reduces the file size and the receiver will receive the complete file these are the protocols at the presentation layer the session layer receives data from the presentation layer it is responsible for managing sessions authentication authorization and creating checkpoints let's first discuss the session management the session layer controls the sessions between devices that are communicating or exchanging data a session is essentially the period of time when two devices start their communication and when they stop communicating or end their communication the session ler is responsible for creating maintaining and terminating sessions it maintains session between communicating devices your computer can communicate with multiple websites or servers simultaneously right you might be logged in to Amazon at the same time you can be browsing other websites such as YouTube Wikipedia Etc to manage this effectively the session layer creates a unique session for each server or device that your device is communicating with it assigns a unique ID to identify each session it maintains separate sessions for each device and keeps track of which data belongs to which session or server the session layer keeps the session open until both devices finish their data exchange when you log out of website or exit the web browser the session layer terminates the session that's the session management now let's discuss authentication authentication is the process of verifying the identity of a user it is typically performed by the server let's understand authentication with real world examples suppose you want to to log in to your Amazon account before logging in you must verify your identity by providing your username and password right after submitting your login credentials Amazon authenticates or verifies your credentials and allows you to log in if they are correct this is an example of authentication in the real world performed by the session layer when authentication is successful the session layer creates a new session the session is typically created after the server successfully authenticates the users login credentials a session represents the period during which a user stays logged into a system or application and the session is terminated when the user logs out of the application now let's move to to the authorization authorization is the process of determining what users are allowed to do after they have been authenticated or logged in for example after you log in to your Amazon account you are authorized to browse and purchase items however you are not authorized to change the price of items authorization determines what actions a user is permitted or not permitted to perform now the next important function of the session layer is creating checkpoints a checkpoint is also known as session restoration checkpoints are a way to save the current state of a session so that uh it can be resumed later even if session is interrupted when a session is terminated abruptly it preserves the session as it was at the time of disconnection or Interruption let's understand this with examples you may have noticed that when you download a file using download managers like IDM or fdm from the internet and your internet connection is abruptly disconnected or disrupted and when you reconnect to the internet again the download resumes from the exact point where it was interrupted it does not start downloading from zero or you can also pause the download and resume it later this is because the session layer keeps track of what has been downloaded by establishing checkpoints in the event of a sudden disconnection or pausing the download these checkpoints help uh resume the session from the last point where the disruption occurred another example that you have likely experienced is when your web browser crashes or shuts down suddenly and when you open it again you may see a restore button right clicking on this button will reopen all the tabs that you had opened prior to the browser's abrupt shutdown this is also an example of session restoration or checkpoints the transport layer receives data from the session layer the functions of the transport layer include segmentation flow control error Control process to process delivery and reliable and unreliable data delivery the transport layer will be covered in two videos this is the first part where we will discuss segmentation and process to process delivery let's start with the segmentation first segmentation simply means dividing data or a file into smaller parts these parts are called segments in technical terms that's why the protocol data unit or data at the transport layer is called segment now why a file needs to be segmented well computers don't send complete files all at once let's say that a wants to send a file to be now the file is not sent all at once instead it is first divided into smaller segments and then each segment is sent independently to the receiver let's understand how segments are created the transport layer receives data from the session layer in the raw form of continuous binaries ones and zeros now the transport layer takes the the bits and converts them into bytes the transport layer deals with data in the form of bytes after converting bits into bytes the bytes are then put into segments each segment is a collection of bytes each segment contains a specific number of bytes the bytes are numbered sequentially within each segment each bite has a unique sequence number assigned to it the sequence numbers help to reassemble data packets or segments in the correct order even if segments arrive out of the order at the destination for the sake of Simplicity let's assume Segment 1 contains five bytes and your sequence numbering starts from 2001 your operating system selects a random number for the first bite and and then increments the number by one for each subsequent bite so the sequence number for the first bite is 2001 for the second it is 2002 and so on until the last bite in the segment which is 2005 in the second segment the sequence numbering continues from where the last segment ended therefore the first bite will have the sequence number 2006 the 2007 and so on until the last bite in the segment which is 2010 this is how sequence numbers are assigned for each segment if there is a third segment its sequence number will start from 2001 because the previous segment ended at 2010 now these sequence numbers help to reassemble the data in the correct order to form the complete file each segment is sent independently to the destination and then reassembled in the correct order to form the original file so to sum up the segmentation in transport layer takes the data or a file then breaks it into many segments and then each segment is sent separately to the re receiver segments are transmitted over the internet to their destination by another protocol called IP in the form of packets now next important responsibility of the transport layer is process to process delivery this is also called end to end or port to port delivery okay let's uh break this down process to process delivery helps devices deliver data to the correct processes a computer typically runs multiple processes simultaneously right a process simply refers to an application program that is running in technical terms when you execute or start a program it becomes a process for example when you start Firefox it becomes a process named Firefox while it runs now think about it you can browse multiple websites in different tabs make video or audio calls and send emails at the same time from a single device right when you have multiple applications or processes running how does the system determine which process to send data to when a system receives data how does it know to which process the data needs to be delivered which process the data belongs to so computers need a way to identify each running process so that data can be delivered to the the correct process to achieve this computers use something called port numbers port numbers identify each running process on a system and help deliver or forward data to the correct process the operating system assigns a unique port number to each running process or network service so after creating segments the transport layer adds the source and destination port number refers to each segment Source Port refers to the port number of the senders device and destination Port refers to the port number of the receiver or destinations device there are a total of 65,535 port numbers however the first 1223 port numbers have specific or predefined rules these ports are reserved for wellknown services such as websites email file transfer etc for example port number 80 is always used for HTTP traffic or websites and port number 443 is the default port for https traffic which is a secure version of HTTP suppose you visit an https website when the request or packet reaches the destination server the request is forwarded to port number 44 3 because port number 443 processes https traffic port number 687 is reserved for emails where it processes the email data now let's understand the entire process to process delivery with real world examples to gain more clarity let's say you want to access google.com as I mentioned earlier the transport layer adds two port numbers to each segment the Source port and the destination port numbers the operating system selects a random port number for The Source Port let's say 1111 Source Port means the port number of the sender device however the destination port number will be 443 because the device is attempting to access Google Google uses https and port number 443 processes the https requests and the default port for https is 443 now when the packet reaches the destination at Google's server there are obviously multiple processes running on the server the server checks the destination port number in the segment which is 443 so it forwards the segment to the process or port number 443 where a program called a web server processes the request now Google sends back the reply to a before sending the reply Google swaps the port numbers this time Google is the sender so the source port number will be 443 and the destination port number will be 11111 now when the segment reaches destination a it checks the destination port number which is 1111 and sends the segment or data to the inter Ed port or process associated with that Port now let's say that device a accesses another website called YouTube in a new tab then the operating system will generate a new random port number for the new tab or website let's say the port number is 2222 so the source or sender port number is 2222 and destination port number is 443 when the YouTube sends a reply back to a a checks the destination port number which is 2022 this time and then forward it to the process or tab associated with the port number which is 2022 and uh the data or segment finally gets displayed in the tab and when you open a new tab or launch another process like Zoom the operating system assigns a unique port number to each process each Tab and process has its own unique boort number acting as a unique identifier that's how data is directed to the correct process by computers now let's move on to the flow control flow control at the transport layer is a mechanism used to control and manage the flow of data between two communicating devices flow control determines the amount of data that needs to be transmitted or sent to the receiver if the sender sends more data than the receiver can handle or process then the data will be lost and wasted flow control makes sure that the sender does not send more data than the receiver can handle or process let's take an example suppose you are downloading a file from the internet the server from which you are downloading the file can transfer data at 100 MVPs rate but your network has a slow internet connection and can only process or accept data at 5 MVPs speed now if the server starts sending data at a rate of 100 Mbps which is significantly FAS faster than your network processing capacity the data will obviously be lost and wasted this is because your device can't process or receive data Beyond its current speed of 5 MVPs now the transport layer controls the data flow how much data should be transmitted to the receiver before sending data transport layer asks the receiver how much data it can process the receiver then informs the sender about its receiving capacity the receiver advertises or tells how much data it can process the sender then sends the data at the rate that the receiver has advertised or informed the sender flow control is managed through window size you will learn more about it in the DCP section this is a basic overview another important function of the transport layer is error control the transport layer makes sure that error-free data is delivered to the receiver if the data becomes corrupted or does not reach the destination or someone modifies the data before it reaches the destination then it is the responsibility of the transport layer to resend the corrupted or lost dat data segments it uses the automatic repeat request algorithm to retransmit the lost or corrupted data the transport layer adds a check sum to each segment to ensure that error-free data is delivered to its destination the check sum essentially checks for any edits or modifications in the data if the data is modified after leaving the senders device the transport layer checks for data modifications at the receiver's device to ensure that the data was not altered or modified if it is found to be modified it is dropped now let's discuss reliable and unreliable data delivery the transport layer provides both reliable and unreliable data delivery depending on the needs of the application we have two major protocols at the transport layer DCP and UDP we also have sctp but UDP and DCP are the most commonly used and dominant protocols TCP and UDP are used for different types of applications TCP protocol provides reliable data delivery meaning that it guarantees that the data will be delivered to the receiver in the correct order and without any errors on the other hand and UDP provides unreliable data delivery meaning that it does not guarantee that the data will be delivered to the receiver now most applications need to receive all of the data in the correct order without any missing parts TCP ensures that this happens the transport layer uses TCP protocol for applications where guaranteed data delivery is mandatory such as emails chat systems web browsing and file downloading etc for example when you download a file from the internet the transport layer uses TCP to ensure that the entire file is downloaded correctly without any missing parts similarly the transport layer uses TCP for other applications such as emails web browsing ATC TCP is a connection oriented protocol because in order to guarantee data delivery TCP establishes a connection between the sender and receiver before exchanging the data now let's talk about unreliable data delivery the transport layer uses the UDP protocol when guaranteed data delivery is not a priority some applications such as live streaming viip audio or video calling and online gaming don't care about the guaranteed data delivery for example if you are watching a live stream and your internet connection stops or you get disconnected for a few seconds when you reconnect the stream will not resume from where you left off instead it will only show you the current live content the packets that were lost during internet disruptions are not retransmitted in this case because if the Lost packets were retransmitted then it would no longer be a live stream UDP keeps sending data regardless of whether it reaches its destination or not UDP is fast it is a connectionless protocol meaning that it does not establish a connection with the receiver like DCP does the transport and all other layers of the OS model relies on protocols to complete tasks each layer has its own set of protocols everything is done using the protocols these are the devices and protocols at the transport layer as you learn more you will start connecting Concepts or dots and making sense of them this is just the beginning the network layer receives data from the transport layer the major resp responsibilities of the network layer include host to host delivery logical addressing routing and fragmentation now let's discuss them one by one starting with host to host delivery host to host delivery means taking data from the sender's device and delivering it to the receiver the transport layer creates segments right now these segments need to be delivered to the destination the transport layer can't do that it only creates segments someone needs to deliver these segments to the receiver this is exactly what the network layer or host to host delivery does it takes segments from the transport layer and deliver each segment as a packet to the receiver's device or another host in a different network the data is called packet at the network layer this is also called source to destination delivery after delivering the data to the receiver the network layer passes the data to the transport layer the transport layer then delivers the data to the exact process or application that requested it this process is called process to process delivery as we discussed in the transport layer process to process delivery only happens after the data reaches the destination device the job of network layer is to deliver data to the destination and then the transport layer delivers data to the exact process this is how both layers work together remember data moves from bottom to up on the receiver's device now let's discuss logical addressing logical addressing is the process of assigning source and destination IP addresses to data segments the network layer receives data segments from the transport layer and then adds the source and destination IP addresses to each segment to form packets the pdu or data is called packet at the network layer the network layer adds the IP address of the sender the device sending the packet and the IP address of the destination device where the packet will be delivered each device that is connected to the internet has a unique IP address an IP address uniquely identifies a device on the internet the IP address essentially determines where the device is located on the internet to deliver data the sender needs to know the destination address therefore the network layer adds the destination IP address to each packet then the packet gets delivered to the destination IP address or device the network layer also adds The Source IP address or the senders IP because when the receiver sends the data back to the sender it also needs to know where the packet should be delivered that's why the source and IP addresses are added to the packets so to summarize IP addresses are added to data so that packets can reach the correct destination That's The Logical addressing now let's move on to routing routing is an important function of the network layer routing is the process of selecting the best possible path to deliver data to the destination the internet is essentially a huge collection of different individual networks or Lan networks all the Lan networks are interconnected Ed these interconnected individual networks form the internet now remember that networks communicate with each other through routers routers communicate with each other to direct or forward data packets to the correct destination packets have to travel through various routers to reach their destination there is never a direct or dedicated link between the sender and receiver data has to go through various networks or routers to reach its destination on the internet let's understand this with an example suppose device a wants to send data to B over the Internet both are located in different networks now data does not travel directly from the source to the destination as discussed earlier it has to pass through various routers to reach it destination so here we have a lot of possible routes now the sender has to select the best possible route to deliver data the job of the routing is to select the best possible route among all the available routes to deliver the data to the destination as quickly as possible in our example routing has selected these three routers that data needs to pass through to reach the destination this is important these routers that the data goes through are also known as nodes or hops the network layer uses various routing protocols to determine the path such as eigrp bgp and rip routing information protocol now let's discuss fragmentation fragmentation is another important responsibility of the network layer fragmentation simply means breaking a packet into smaller pieces or fragments now why do packets need to be fragmented the transport layer also breaks a file into smaller pieces or segments right which is called segmentation but there is a difference segmentation means breaking a file into smaller pieces or segments at the transport layer and fragmentation means means breaking a segment or packet into smaller pieces at the network layer the fragmentation is required in certain cases because a single packet can carry a maximum of 1,500 bytes however there is a new technology called jumbo frames that can carry up to 9,000 bytes in a single packet the jumbo frames are mostly used by data centers for now they are not common at all a single packet can carry a maximum of 1,500 bytes which is the current standard this is also called MTU maximum transmission unit MTU defines the total data that can be transmitted or sent in a single packet now each network has its own MDU or capacity to handle data in a single packet let's say the sender sends a packet of 1,400 bytes to the receiver but the receivers network has an MTU of 700 bytes the receiver's Network only accepts a maximum of 700 bytes in a single packet the receiver will not be able to process or handle a packet with 1,400 bytes because its MTU is 700 bytes now the sender has to figure out a way to cut down packet size to meet the receivers MDU so to prevent this problem the network layer uses fragmentation it takes the packet of 1,400 bytes and divides it into two smaller packets of 700 bytes each now the fragmented packets are sent to the destination and reassembled at the receiver's device to form the original packet so this is called the fragmentation breaking a packet into smaller pieces to meet the receivers MTU the most important protocol at the network layer is the Internet Protocol or IP the IP protocol manages fragmentation assigning IP addresses Etc these are the protocols and devices present at the network layer the route is the most important device at the network layer it is the router that forwards the data packets to the destination the data link layer receives data packets from the network layer and the responsibilities of the data link layer include node to node data delivery flow control error control physical addressing Framing and media access control so let's start with node to node delivery node to node data delivery means that the data link layer delivers data from one node to another now what is a node a node is a device that is part of a network and capable of forwarding and receiving data such as a phone computers servers switch router modem Etc now let's understand node to node delivery in the context of the data link layer if you recall from the network layer the network layer selects the route or path that data packets must go through to reach their destination right let's say that Network layer selects this route to deliver data from the source to a destination here we have four routers between the sender and receiver the data must pass through these four routers to reach its destination now these routers are also called nodes or hops I will use the term nodes from this point forward because node is the terminology we use for routers in the data link layer now if device a wants to send data to B the data will not travel directly from A to B instead it has to go through these nodes to reach the destination the responsibility of the data link layer is to deliver data from one node to another or the next node that is on the way to the destination when data leaves the senders device the data link layer delivers the data to the first node node one will then forward the data to node two and node two will further forward it to node three eventually the data will reach its destination that's the node to node or hop to hop data delivery don't confuse node to node delivery with host to host delivery which we have at the network layer the network layer directly communicates with the receiver or destination device and the data link layer takes care of the nodes or the next node that is on the way to the destination both layers at different levels take care of the data delivery from sender to receiver remember when devices on the same network want to communicate with each other they can directly communicate using the data link layer with the help of Mac addresses the network layer is not required for sending data to each other within a single Network however the network layer becomes essential when delivering data to devices located on different networks now let's discuss the flow control we also have flow control at the transport layer right flow control by definition serves the same purpose at the both layers flow control makes sure that the sender does not send more data than the receiver can handle or process however there is a minor difference the transport layer directly controls the data flow between the sender and receiver devices it ensures that the sender does not send more data than the receiver can process now before data can reach the receiver's device it must pass through nodes that are on the way to its destination right therefore we need a way to control the flow of data between these nodes as well this is what the data link layer does it controls the data flow between nodes flow control in the data link layer ensures that the sender node does not send more data than the receiving node can handle or process it uses various algorithms to control the data flow such as stop and wait again the data link layer controls the flow of data between nodes while the transport layer controls the flow of data between the sender and receiver now let's discuss error control just like the transport layer the data link layer also checks the data for errors however there is a difference the transport layer checks the data for errors when it reaches the destination device but before the data reaches the actual destination it goes through these hops or nodes right so similar to flow control the data link layer checks for errors in the data at each node I will explain in a minute why both layers check for errors error control in the data link layer is the process of detecting and correcting corrupted or lost data frames at each node the data link layer uses a variety of techniques to detect and correct errors such as parity check and cycle redundancy check the most common types of errors that can occur at the data link layer include single bit errors burst errors and frame loss the reason OSI model checks for errors at both transport and data link layer is simple it improves the efficiency Suppose there are no error checks at the data link layer or nodes the data with errors reaches the destination device and the receiver checks and detects errors after detecting an error the receiver requests the sender to resend the corrupted data this is a time consuming process because the receiver's request has to travel back through all the nodes along the path however detecting errors at a node before the data reaches the destination can fix them sooner the node can request the sender to correct the error or resend the corrupted data this saves time and improves efficiency now let's discuss physical addressing and framing physical addressing is the process of assigning Mac addresses to data packets the data link layer assigns the Mac addresses of sender and receiver to each packet that it receives from the network layer to form frames data unit it is called the frame at the data link layer Mac address is also known as physical address Mac address is a unique 12 digit hexadecimal number embedded into a computer's network card a MAC address is permanently assigned to a network card and can't be changed if two devices on the same network want to communicate with each other they can communicate using their Mac address data exchange within the same network can be facilitated using Mac addresses without requiring Network layer and IP addresses as I mentioned the data or pdu at the data link layer is called the frame the data link layer converts packets into frames it receives packets from the network layer and wraps them into frames the data link layer properly formats data before it is sent to the physical layer this process is called framing just like the network and transport layer the data link layer also adds its own data or header to each packet that it receives from the network layer the data link layer adds a header and a trailer to a data each frame contains a frame header frame body and a frame trailer this is the structure of a frame the header includes the Mac addresses of the sender and receiver devices as well as flow control information the frame body contains the data or payload to be delivered to the destination the packet that data link layer receives from the network layer is stored in the body or payload of the frame it also adds a trailer at the end of each frame trailer includes error detection codes we will get back to the frame structure in a dedicated video there is more to frame than just these fields now let's move on to the media Access Control data link layer is divided into two sub layers logical link control and media Access Control LLC handles protocols synchronization flow control and error detection EDC media Access Control manages data collisions let's understand what data Collision is suppose devices are connected to a network through a shared cable such as in bus topology where devices connect and communicate with each other through a thick wire or cable now in this type of network Things become problematic when multiple devices attempt to send data simultaneously ly when multiple devices send data at the same time the data can Collide which causes data loss so in order to send data each connected device has to access or use the shared cable when no other connected device is using it or sending data media Access Control makes sure that only one device sends data at a time to avoid data Collision media Access Control makes sure that devices don't interfere with each other's data which allows each computer to send and receive data without interference data is transmitted by a device only when the shared cable or link is idle and no one else is using it the technology used for avoiding data Collision is CSM A/C D it stands for Carrier sense multiple access Collision detection these are the protocols and devices at the data link layer the network interface card is the most important device at the data link layer any device that deals with Mac addresses is a data link layer device another very important device at data link layer is the switch which intelligently forwards packets based on the destination Mac address ensuring efficient traffic flow within a network now the last or the first layer from the bottom is the physical layer the data link layer prepares data to be sent over wires it makes sure that the data is properly formatted so that it can be transmitted over the wires or physical mediums the physical layer receives data from the data link layer and is responsible for for transmitting data over physical mediums such as wires or wireless radio waves the physical layer interacts with the Hardwares that are used to send receive or carry data such as cables Optical fibers and radio waves it is responsible for converting Digital Data into electrical or Optical signals that can be transmitted over physical mediums before transmitting data to the actual physical infrastructure the physical layer generates signals based on the medium that a device is using to connect to the network or access the internet the physical layer receiv receives data from the data link layer in the form of binary zeros and ones this is Digital Data or digital signals however ones and zeros can't be sent over transmission mediums such as cables or radio waves Etc the physical layer must convert Digital Data into signals that can be sent over the physical medium which depends on the type of connection being used for example if you are connected to the network through Wi-Fi then the digital signals are converted into radio signals or radio waves and if you are connected through an ethernet cable the data is converted into electrical signals this conversion is done by modem after converting the data into the appropriate signals the physical layer transmits the data over the physical medium from one node to another and eventually data reaches at the destination the data is called bits at the physical layer how data is received and processed at the destination it will be covered in the encapsulation and decapsulation video These are the devices and protocols present at the physical layer you might be wondering why hubs are physical layer devices while switches are data link layer devices a switch can read Mac addresses and forward packets to the correct destination device based on that address on the other hand hubs can't read Mac addresses so they forward every packet to all devices connected to them remember anything that deals with Mac addresses is a data link layer device and hubs are physical layer devices because they can't read Mac addresses in this section we will dive into the fundamentals of cryptography cryptography is a critical component of secure data Communication in modern Computing it is absolutely unnecessary you don't have to master it however understanding the fundamentals of cryptography is essential for everyone especially for cyber security and network engineers in this first video we will explore what cryptography is and why it is important or required so what is cryptography cryptography in simple terms protects data it allows devices to communicate securely over the Internet it protects data from cyber criminals middleman or hackers let me first demonstrate data communication over the internet without cryptography then we will be able to understand why it is needed suppose device A and B want to communicate over the Internet a sends a Hello message to b now the data does not travel directly from the sender to receiver on the internet instead it goes through various devices and networks to reach the destination we don't know who can intercept the data as it travels to its destination now what if a cyber criminal intercepts the communication then the hacker will be able to read all the details or data that the communicating devices exchange between them intercepting data is not that difficult if you have basic hacking skills you can intercept data easily the problem becomes even more critical when users connect to important websites like banking portals Gmail or social media platforms interception of data communication with banks or other sensitive websites by hackers can have severe consequences and compromise your personal information we have no control over who might intercept data because by Design the internet is accessible to everyone however we can protect the data itself so that even if someone intercepts it they can't understand the original message or information the real problem here is the communication of data in plain text devices are sending and receiving data in plain text so whoever intercepts it can easily read the original data being exchanged therefore we needed a secure method for safeguarding and exchanging data this is where cryptography steps into address the problem cryptography encrypts the data before it is sent to the receiver after encrypting the data becomes unreadable like this the Hello message gets scrambled into this unreadable encrypted text now this encrypted message is then sent to the destination now even if cyber criminals intercept the data they will not be able to read the original data all they will see is the encrypted data the data is decrypted or converted back to its original form only at the destination this is the magic of cryptography only the receiver can decrypt data back to its original form so that's how cryptography protects data and ensures it is delivered securely to its destination this is a basic technical overview of cryptography we will dive into more details in the upcoming videos so let's start with encryption encryption is the process of transforming plain text or readable data into unreadable data to secure it from unauthorized access let's say the sender wants to send a Hello message to the receiver now before sending the message to the destination encryption scrambles or encrypts the message into unreadable random characters like this so that only the authorized or intended receiver can read it data is encrypted in a way that only the intended receiver can read the original message this encrypted data is then transmitted to its destination now if hackers hack or intercept the data they will not be able to read the original message attackers will still be able to access or view the data but all they will C is the encrypted message not the original data now decryption is the opposite of encryption once data is encrypted it is sent to the destination and at the destination the encrypted data needs to be decrypted so the receiver can read the original message now the process of converting encrypted data back to its original form is called decryption remember remember only authorized users can decrypt the data data is always decrypted at the destination now let's discuss the difference between encryption and cryptography cryptography is a broad term that includes everything related to data security encryption is essentially a component or part of cryptography cryptography on the other hand covers everything related to data security including encryption and decryption along with all the necessary steps involved in the data security process so cryptography is a comprehensive term that includes everything related to encryption and decryption both are integral parts of cryptography when it comes to encryption there are two primary types symmetric and asymmetric encryption in this video we will focus specifically on symmetric encryption and how it works now symmetric encryption is also known as symmetric key encryption it uses a single key to encrypt and decrypt data the word symmetric means the same therefore symmetric key encryption uses the same key to both encrypt and decrypt data this key is also known as the secret key the concept of the key in symmetric encryption is is very similar to a door key we use the same key to both lock and unlock the door right only the key that locks the door can unlock it the same principle applies to symmetric key encryption the same key is used for both encrypting and decrypting data and no other key can perform these functions the data is encrypted using complex encryption algorithms an encryption algorithm is essentially a technique or a set of steps used for scrambling or encrypting data there are many encryption algorithms used in symmetric encryption such as AES Dees Blowfish ATC to encrypt data in real world applications now I will explain symmetric key encryption using the simplest and oldest encryption algorithm this will help us easily understand the process and how an encryption algorithm and a key work together to encrypt and decrypt data encryption Is Not A New Concept it has been used for centuries to protect information even before computers and Digital Data existed the first noun data encryption method was used by Roman King Julius Caesar the technique or encryption is also known as Caesar Cipher the Caesar Cipher is one of the simplest and oldest encryption methods named after Julius Caesar who used it to protect his military messages such as when to attack Retreat Etc Caesar Cipher serves as a foundation for understanding the concept of symmetric key based encryption now let's understand metric key encryption using the seizure Cipher let's say that device a wants to send the message hellow to device B securely as I mentioned at the beginning the message is encrypted using a secret key in symmetric encryption let's say the secret key is two now the encryption algorithm or ciss Cipher works by shifting letters forward by a fixed number of of positions in this case we are using two as a shift value so it will move each letter two positions forward scissor Cipher is also known as scissor shift or shift Cipher the algorithm specifies shifting or moving letters forward by the secret key value for encrypting data in my case the secret key is two so we will move each letter forward by two positions so if you move H2 positions forward it becomes j e becomes g l l becomes NN and O becomes Q so this is the encrypted data or text hello has been encrypted into this now remember this is very important this encrypted text or message is known as the cipher text in cryptography cyer for text is basically the encrypted message or data now after encrypting the data a sends the cipher text to the destination the receiver uses the same secret key which is to to decrypt the data to its original form by reversing the process the encryption algorithm involves shifting each letter two positions forward in the alphabet to encrypt data right now to decrypt the message the algorithm reverses this process by shifting each letter two positions backward for example the J becomes H and the letter G becomes e the letters NN becomes l l and uh Q becomes o now we have successfully restored or decrypted the cipher text to its original form hello this process is known as decryption so that's how the algorithm and key work together the algorithm specifies the shifting of letters by the shift value while the shift value itself is the secret key now if a wants to communicate with other device it generates a unique secret key for each connection computers or devices in the real world don't use or rely on simple encryption methods like the cesure cipher to encrypt data because the cesure cipher can be decrypted very easily the cesure cipher method is a valuable tool for explaining the concept of symmetric key based encryption the encryption algorithms utilized by computers involve highly complex mathematical equations encryption algorithms that computers use such as AES and Blowfish Use sophisticated mathematical calculations to encrypt data AES is the current industry standard and is highly secure it is used for securing communication now let's address the very important question how does the receiver know or obtain the secret key as we discussed earlier both the sender and receiver need the same Secret key to encrypt and decrypt data right if the sender uses two as the secret key to encrypt data then the receiver needs the same key to decrypt the data this means we somehow need to share the secret key with the receiver so it can decrypt the data using the same key that encrypted it however sending the secret key directly to the receiver is not safe let's say if the sender sends the secret key directly along with the data to the receiver then hackers can intercept both the secret key and the cipher text consequently they can easily decrypt the message using the secret key that's why the key is not sent directly from sender to receiver instead the key is exchanged or established securely using the Dy Helman protocol the Dy Helman protocol uses complex mathematical equations that allow both the sender and receiver to independently establish the same secret key without directly sharing it so defy Helman essentially helps both the sender and receiver establish the same secret key without directly exchanging it remember remember the secret key is always established before both the sender and receiver start exchanging actual data after establishing the key both devices then begin exchanging data securely it is a proven method for key exchange and is considered extremely difficult for a third party to intercept or predict the key that's it for this video guys let me know if you come up with question before we dive into the specifics of asymmetric encryption let's first understand why it was developed asymmetric encryption was developed to address the limitations of symmetric encryption as we discussed in the previous video symmetric encryption requires the sender and receiver to share a secret key before secure communication can begin the key exchange is typical secure but there is always a potential risk of compromise both symmetric and asymmetric encryptions have their distinct applications and uses asymmetric encryption solves the key sharing problem of symmetric encryption asymmetric key encryption is also known as public encryption because it uses two separate keys to encrypt and decrypt data the public key and the private key the public key is typically used to encrypt the data and the private key is used to decrypt it the public key as the name suggests is either publicly available or shared with authorized recipients or receivers the corresponding private key is kept private and is not shared with anyone now let's understand the essential fundamental terms of a symmetric encryption before diving into how it works let's say a wants to send hello to device B now before exchanging the data both devices will generate two keys each the public key and the private key the public and private keys of each device work together because they are always mathematically related or linked together remember this point it is very important in asymmetric encryption suppose if device a encrypts its data with its public key then that data can only be decrypted using its private key no other key can decrypt it similarly if a encrypts data using its private key then the data can only be decrypted using its public key as I mentioned earlier both keys are mathematically linked together so if you encrypt data with one key then only its corresponding key can decrypt that data the same applies to B and all other devices that use asymmetric encryption if B encrypts data using its public key then only its own private key can decrypt the data and vice versa in the real world the public key is always used to encrypt data and the private key is used to decrypt it therefore the public key is shared with other devices now let's see how the entire communication is securely carried out using asymmetric encryption suppose a wants to send the Hello message securely to B using asymmetric encryption the first step in asymmetric encryption is that both the sender and receiver generate two keys each a public key and a private key now after generating Keys both A and B will exchange their public Keys a will send its public key to B and B will send its public key to a after receiving the public key of B A will use public key of B to encrypt its data the Hello message will be converted into Cipher text after encryption now the encrypted data or Cipher text is sent to B now how does B decrypt the data B has two keys its own private key and the public key of a right remember the data B received was encrypted using its public key which it sent to a now only the private key of B can decrypt the data because it's the only key mathematically linked to it B already has that private key it shared its public key and kept the private key so obviously B decrypts the data using its private key because the data that is sent was encrypted using its public key so the private key of B will decrypt the data back to its original form hello the public key can't because it is not mathematically linked uh to the key that encrypted the data so basically B says to a take my public key then encrypt the data that you want to send to me with it and then send it to me so I can decrypt it using my private key similarly if device B wants to send data to device a it will use the public key of device a to encrypt the data upon receiving the data device a will use its own private key to decrypt it so to summarize in asymmetric encryption both the sender and receiver exchange their public keys before exchanging data so the sender can encrypt the data using the public key and then corresponding private key is used for decryption that's why a symmetric encryption is considered more secure compared to symmetric encryption because you never need to share the private key that decrypts the data the algorithm that powers a symmetric encryption is r a RSA encryption is an asymmetric encryption algorithm named after its three inventors riest Shamir and Adelman asymmetric encryption uses RSA to securely exchange data over the internet in this section we will learn about hashing this is the first video on hashing and in this video we will understand what hashing is and why it is needed similar to symmetric and asymmetric encryptions hashing protects data hashing is also a fundamental part of cryptography however hashing is slightly different from encryption so let's first understand what hashing is in cryptography hashing is a technique that takes data or a message as input and generates a fixed size output it takes any given input and transforms it into a random fixed value output representing the data in a condensed form I know it sounds confusing and overwhelming right now but don't worry I will explain how it works in the next video everything will become clear once you learn it's working so there is no need to feel lost at this point for now the important thing is to understand the problems that hashing solves and why it was developed hashing addresses two major problems data Integrity storing and verifying passwords securely let's first discuss the important part data Integrity we hashing plays a crucial role data integrity means that the receiver receives error free and unaltered data hashing ensures that data remains unaltered or unchanged during transmission or storage let's say device a wants to send a file to B now if a cyber criminal intercepts the file and modifies the file contents then sends the modified file to the intended receiver it compromises the files Integrity the receiver will not be able to determine whether they received the original or modified file therefore we need a mechanism to check the Integrity of files of data this is precisely the problem that hashing addresses it ensures that original valid and unaltered data reaches the intended destination by detecting any changes or modifications that may have taken place during transmission another crucial application of hashing is securely verifying and storing passwords web and other applications rely heavily on hash for secure data storage particularly passwords hashing essentially provides an additional layer of protection this will be discussed in a dedicated video later in the section Beyond these crucial applications hashing has a wide range of other use cases in cryptography such as digital signatures secure key derivation random number generation Etc in this video we have a lot to cover we will start by exploring the fundamentals of hashing how it works how it protects the Integrity of files or data and what a collision is hashing is a complex mathematical process that takes an input of any size and produces a fixed size output called hash value here is how hashing works we provide input or data to a hashing function hashing functions are responsible for generating hashes the input can be anything a single letter word a paragraph a text file PDF file or any other data regardless of the inputs size the hashing function always produces a fixed length output for the sake of Simplicity let's assume that we have a hashing function specifically designed to generate a fixed length out output of 10 random characters this means that regardless of the input you provide to this function it will always produce an output with a fixed length of 10 unique random characters so if your input is a single character such as B this hashing function will produce a 10 character random string like this as its output now let's increase the input size suppose the input is the word hello the output will be different such as this however the output length will always be a fixed 10 character long random string even though the input size has increased the hash will always produce a fixed length output of 10 characters similarly if you provide a file as input the function will still produce a 10 character long output now in the real world also hash functions consistently produce fixed length outputs regardless of the length of the input this applies to all types of data and files including large files with sizes in gigabytes the functions will still generate a fixed size output that's the fundamental nature of hashing functions there are numerous hashing function used in various real world applications such as md5 Sha 1 sha 2 and sha 256 all of these functions produce a fixed size output however the exact output size varies depending on the specific hash function being used we will discuss them in more detail in the upcoming videos practically for now let's dive more closely into the inner workings of hashing to illustrate the hashing process in a clear and understandable way I will use a very simple hashing function as an example this hashing function works by taking the position of each letter and then adding them together to generate the hash so here we have letters along with their numerical positions let's say I want to generate hash for the Hello message the letter H is at the eth position so I will take the value 8 e is at the fifth position L is at the 12th position since there are two L's it is 12 again o is at the 15th position so if we add all these numbers we get 52 now the result or output that a hash function produces is called a message digest the message Digest is also known as a checkm digital fingerprint or simply hash value now the 52 is basically the hash value or fingerprint of the word hello so this 52 essentially represents this message as I mentioned in the previous video hashing is used to ensure data Integrity it guarantees that data remains unmodified when transmitted from sender to receiver here is how it works when data or a file is sent from one device to another a hash value is also transmitted alongside it suppose device a sends the Hello message to device B it will also send the hash value calculated for hello which is 52 now when Hello reaches B the receiver also calculates the hash value of hello independently using the same function that was used to calculate the hash by the sender now after calculating hash it gets 52 now it compares the hash value that it calculated to the value sent by the sender if the hash value the receiver receives matches its own calculated hash value then it means the file or message was not modified it received the correct message now let's say before the message reaches the actual receiver a hacker intercepts it modifies hello to hell and then sends this modified message to the receiver now the receiver calculates the hash this time it will be 37 the hash value for hell is 37 when the receiver Compares this new hash value with the hash sent by the sender it will not match this is because the message has been modified resulting in a different hash if the modification is detected then the message gets dropped or discarded remember even a minor change produces a different hash value which helps to detect changes in a file or data in the real world you may have noticed that when you download files from reputable websites they often provide a hash value alongside the file itself this hash is typically displayed on the website or included in a separate file after downloading the file you are encouraged to calculate the hash of the downloaded file using the same hash function that the website or application used to generate the original hash if the hash you calculate matches the hash provided with the file it is a strong indication that you have downloaded the correct file without any corruption or tampering so guys that's how hashing works and ensures the data Integrity obviously this is the simplest possible hash function such simple functions are not used in real world applications this was just for explanation purposes this function is very weak predictable and easy to crack in the real world hash functions such as Sha one sha 56 use very complex mathematical calculations to produce a hash or message digest data is put through a complex process to produce a hash now there are several criteria that a hash function must meet to be considered secure and reliable for world use let's take example of our simple hashing function this function produces 52 hash value for the word hello right now there are many words that can add up to 52 for example two Zs can also produce a hash value of 52 and the word zebra also adds up to 52 along with many other combinations this is called Collision a collision in hashing occurs when two different pieces of data or message generate the same hash value using the same hash function this hashing function is also producing the same hash values for different messages this is bad if two different pieces of data have the same hash value or generate the same hash comparing their hashes will not not tell us which one is the original this can lead to falsely accepting corrupted data as valid potentially causing major issues so this function is obviously not suitable for real world applications because it is not secure is easily predictable and easy to crack therefore a hash function must always produce a unique hash value or output for every distinct or indiv visual input this is the first and most crucial criteria another very strict requirement for a hashing function is that it must always produce a fixed length of output my simple hash function will not produce a two-digit output or hash value if I provide a line or paragraph as an input the output will be three digits or more but in real world a hash function always produces output of a fixed length no matter how long or small the input is it must always produce a fixed length output so guys to summarize a hash function must produce a unique output for every distinct input and every output must be of a fixed size command ping is one of the most commonly used commands in Linux networking it is pre-installed on all three major operating systems Windows Mac OS and Linux ping is a simple yet very important command it is a network connectivity tool used to check network connectivity and troubleshoot issues let's say you are experiencing problems related to your internet connection in such situations you can use ping command to determine whether your internet connection is working or not ping can also be used to check websites if you are having trouble accessing a website you can use ping to verify whether the website or server is up and running now let's jump into the practicals type ping space and we need to provide an IP address or a domain name to the Ping command so let me specify let's say google.com the way ping command works is it essentially sends icmp packets to the specified host or destination and then waits for response from the specified host let me press enter by default the Ping command keeps running forever you have to stop it manually so to stop the Ping command press controll plus C together and at the bottom we have the statistics for the connection ction 14 packets transmitted it means my system sent 14 packets to the google.com and 14 received it means all the packets that ping sent to the Google Google responded to all those 14 packets now it proves two things one my internet connection is working because in order to send packets out on the internet you need to have a working internet connection it also proves that Google is up and running because it responded to the packets which were sent by ping so both systems communicated successfully over the internet now as we saw the default ping command sends unlimited packets now let's do some customization I only want to send a limited number of packets so type ping hyph C5 google.com this time ping is only going to send five packets or whatever number you specify after The Hyphen C parameter so let me press enter as you can see it sent five packets and received all those five packets so guys that's how you can check your inter internet connectivity if your system is able to send packets out in the internet it means that your internet connection is working just fine and of course if it receives packets from the host that you provide to Ping command it also means that the host that you are connecting to is also up and running now if your internet connection is not working then you will see messages or error messages like this temporary failure in the name resolution remember this message can also appear if you provide a wrong host name or domain name that doesn't exist this is the typical error message when your internet is not working now let's say if the host that you are connecting is not up and running then in the statistics section you will see something like zero packets received it means me that the host is not up and running or there could be another reason maybe the host that you are connecting to or pinging to has blocked the icmp packets the common response if host is not up and running or is down you will see the zero packets received in this section we will get started with the binary number system in this particular video we will learn what is number system is and the types of number systems used by computers if you are a complete beginner the binary number system might seem scary or intimidating but don't worry everything has been simplified for you just pay attention before we get into the binary number system let me explain what a number system is in general to set the context and groundwork for understanding the binary number system some of you might find this too basic I believe it is important to cover the absolute fundamentals to ensure everyone including complete beginners feels comfortable and well equipped to learn a number system is a way of representing numbers using specific symbols or digits such as 0 1 2 3 4 5 6 7 8 and 9 we use these digits to represent or write all the different numbers we can think of right now there are several number systems that are specifically used by computer systems including decimal binary octal and hexadecimal let's start with the number system we are all familiar and comfortable with which is the decimal number system the decimal is a base 10 system so what is base first base in the this context refers to the total number of digits used to represent numbers base 10 therefore means the decimal number system uses 10 digits from 0 to 9 to represent numbers the 10 digits that decimal uses are 0 1 2 3 4 5 6 7 8 and 9 0 is also counted so from 0 to 9 there are 10 digits that decimal system uses we can represent or write any numbers using these 10 digits such as 6 7 23 100,000 or any number that you can think of all numbers are represented using combinations of these 10 digits we use the decimal number system in our daily lives to count things right and it works pretty well for us humans now computers use the decimal number system for displaying information in a human readable format when you see any information that contains numbers it is the decimal number system in use now let's move to the main part of the video the binary number system the binary number system is a base two system meaning it uses only two digits to represent numbers those digits are 0 and one the decimal system uses 10 digits from 0 to 9 to represent numbers on the other hand the binary system only needs two digits 0 and one with these two digits we can represent or write any number through combinations of 0 and one in upcoming videos we will learn how to convert any decimal number into its binary equivalent now the binary number system is used by computers and All Digital devices you may have heard that computers only understand binary right binary is basically the language of computers now what does it actually mean when we say computers only understand binary data is stored transmitted and processed only in binary by computers everything stored in computers from characters audio to video files and images is represented using binary This Means Everything ultimately gets converted into combinations of zeros and ones for example when you save an image on your computer it is first translated or converted into binary before being stored in the system similarly all types of data are converted into binary before being stored or processed when a computer performs any task or calculation the data is first converted into binary then it is processed in short everything is represented by combinations of just two digits one and zero computers use only binary numbers for processing and storing data now the binary number system is very important in networking specifically for topics like IP addressing CER notation Network masks subnetting Etc with need to understand how to convert decimal to Binary and binary to decimal when working with IP before addressing then we have the octal number system octal is a base eight system there are a total of eight digits that can be used in octal 0 1 2 3 4 5 6 and 7 these eight digits are used to represent numbers however octal is no longer as widely used in Computing as it was in early Computing the next number system is hexadecimal in the next video we will cover hexadecimal in detail because it deserves a dedicated video let's begin by understanding what hexadecimal is we don't need to learn the in-depth workings of hexad decimal we only need to know its uses where it is used and why it is preferred in certain situations that is sufficient hexad decimal is a combination of two words hexa and decimal hexa is a Latin word that means six and decimal as we know is a base 10 number system right so if you add up hexa which is six and decimal which is a base 10 we get 16 therefore heximal is a base 16 number system system hexadecimal uses 16 digits to represent numbers or data these digits are 0 1 2 3 4 5 6 7 8 and 9 these are decimal numbers right now the remaining six are letters a b c d e f so we have all the decimal numbers in hexadecimal plus six letters now a represent 10 in the hexadecimal system B represents 11 C represents 12 D represents 13 e represents 14 so hexadecimal uses these 16 digits to represent numbers and other data now let's discuss the actual question what are the use cases of hexadecimal numbers and where do they fit in hexadecimal numbers have a wide range of applications the hexadecimal number system represents binary and decimal data in a more concise and readable format let's understand the real world use of hexadecimal with Mac addresses so now what I'm going to do is open my command prompt and show you the MAC address what it looks like so press Windows key type CMD click on command prompt type ip config for/ all press enter and under the wireless land adapter Wi-Fi locate the field physical address now this is the MAC address as you can see it is in hexadecimal digits a MAC address is always represented using hexadecimal digits a MAC address is a 12 hexadecimal digits along which means it has six pairs of two hexadecimal digits right as you can see here now if the same Mac address were represented using the decimal number system we would need more than 12 digits probably around 18 digits to represent a MAC address the hexadecimal system precisely represents data in fewer digits compared to heximal hexadecimal numbers are also commonly used in memory addressing data compression and even color codes you have likely seen codes that look like this these codes use exm system if you are a web developer you must have used color codes right color codes are written in hexad deiml because they can compactly represent the color codes understanding binary to decimal conversion and vice versa is crucial for working with IP addressing subnetting and other related topics it may sound challenging but it is actually simple there are several me methods for converting decimal to Binary but I will show you the simplest one now I want to convert this binary number 0 0 1 0 1 0 1 into decimal the binary is a base to number system which means it uses only two digits zero and one to represent numbers each digits value increases by a factor of two or doubles as you move leftward in the number now let's get down to the real work without complicating it so let me write the binary number that I want to convert into decimal which is this it is an 8 bit number now to convert underneath the rightmost digit right one start with one and as you move to the left multiply the number by two 1 multiplied by 2 is 2 2 * by 2 is 4 4 into 2 is 8 8 into 2 is 16 16 * 2 is 32 32 into 2 is 64 64 * by 2 is 128 keep multiplying the previous number by two until you reach the leftmost binary digit since we are dealing with only eight binary digits the multiplying or doubling stops there there is no need to continue beyond the last bit we now have the place value for each binary digit if there were another binary digit we would need to multiply by two again to get its place value which would be 256 since we are working with an 8bit binary number we don't need another value now we have everything needed to convert this binary number to a decimal number to convert binary number to decimal first identify the binary digits where there is a one we have a total of four ones now Mark or Circle all the place values where there is a one in the binary number essentially Circle all the decimal values that correspond to the ones after marking the place values that correspond to ones add up the marked values this this will give you the decimal equivalent of the binary number this is as simple as that the method is simple if a binary digit is one its corresponding decimal value is included in the final sum and if the binary digit is zero its value is not added to the sum let's add these marked values or numbers that are underneath the ones so 32 + 8 + 2 + 1 is 40 3 so decimal equivalent of this binary is 43 so this is as simple as that now let's look at one more example for clarity we will once again convert an 8bit binary number to decimal the reason for specifically working with eight digits is that we commonly deal with 8 bit numbers in ipv4 addressing subnet masks subnetting and related topics most of the time we need to convert 8bit binary to decimal and decimal to Binary let's say we have a given 8 bit number 1 0 0 1 0 1 1 zero the method for conversion Remains the Same underneath the rightmost digit start with one as you move to the left multiply the number by two 1 multiplied by 2 is 2 2 into 2 is 4 4 * 2 is 8 8 * 2 is 16 then 32 * by 2 is 64 and 64 into 2 is 128 now we have the place value for each binary digit now Circle the decimal numbers underneath the ones 128 16 4 and two now adding them together we get 150 therefore the decimal equivalent of this binary number is 150 in this way you can convert any 8bit binary number into a decimal and of course if you are given a longer binary number then add the place values by multiplying the previous value by two we can also do quick mental calculations just memorize the place value of each digit and add them where the digit is one with practice it can be achieved easily so that's all you need to know when it comes to binary to decimal conver verion for ipv4 addressing We are continuing where we left off in the previous video in this video we will learn how to convert any decimal number to Binary let's say we have a decimal number 59 and we want to convert it into binary the process is similar to the binary to decimal conversion this time to convert the decimal number to Binary we first need to start by writing out the place values starting from the leftmost digit write one in the one's place and then multiply each subsequent place value by two as we move left 1 * by 2 is 2 2 * 2 = 4 4 * 2 is 8 8 into 2 is 16 16 into 2 is 32 32 * 2 = 64 and 64 * 2 = 128 these 8 consecutive powers of two provide enough place values to represent any decimal number less than 256 now to convert 59 we need to find the binary digits or bits that we can add up to create the number 59 the process is straightforward we identify numbers that can be used to reach the target number without exceeding it we start with the largest number which is 128 in our case since 128 is greater than 59 we can't use it to get or reach 59 if we can't use a number we put a zero under it if it is used then we write one so zero here the same goes for 64 it is greater than 59 so we can't use it again put zero under it now we have 32 yes 32 can be used to reach 59 so put one under that number next is 16 can it also be used the answer is yes since 32 + 16 is 48 Which is less than 59 we can use it so put A1 under 16 remember if adding a number exceeds our Target we have to write zero and we use one when a number can be used to reach the target without going over next is eight can we use eight yes we can 48 + 8 is 56 so put one under 8 then we have four can we use 4 no we can't adding 4 to 56 would result in 60 which exceeds our Target number 59 so put a zero in the corresponding position moving on to two can be used it yes 56 + 2 is 58 so put one under 2 then we have 1 can we use it yes 58 + 1 is 59 therefore we place a 1 in the one position so this is the binary representation of 59 0 0 1 1 1 0 1 1 so guys this way you can convert any number from decimal to Binary now let's convert one more decim deal to Binary let's say 171 the process is the same we need to identify numbers that can be used to reach the target number without exceeding it again we start with the largest number which is 128 since 128 is less than 171 we can use it to reach 171 therefore the right A1 in the corresponding position next is 64 adding it to 128 would exceed our Target so we skip it and write a zero in its position or beneath it moving on to 32 adding it to 128 gives us 160 which is still less than 171 therefore we use 32 and write a one in its position next number is 16 adding it to 160 results in 176 exceeding our Target number 71 so we skip it and write a zero in its position next is 8 yes 8 can be used to reach 171 160 + 8 is 168 so we write one under it next is two yes two can also be used to reach 171 168 + 2 is 170 so we use it and we write one under it finally one is all we need to reach 171 therefore we write 1 in its position 1 170 + 1 is 171 so 1 1 0 1 0 1 is the binary equivalent of decimal 171 now this is an 8 digigit number so highest number an 8 bit binary number can represent is 255 if if you add all the digits together you get all possible combinations from 0 to 255 therefore these eight bits can represent numbers from 0 to 255 if you need to represent a number larger than 255 you will need more than 8 Bits all we need to do is increase the number of bits for example adding just one more bit or ninth bit allows us to represent numbers from 0 to 511 you can simply add bits as needed to handle larger numbers I specifically used 8 Bits because 8bit binary conversion is heavily used in subnet masks and subnetting each part in an IP address or subnet mask uses 8 Bits called an octet therefore for these applications understanding 8bit conversion is sufficient and you don't need to dive into advanced algebra it is more than enough in this video we will learn about two operators the or operator and the and operator both of these operators are also known as logical operators specifically the end operator plays an important role in ipv4 addressing especially for tasks like identifying Network IDs subnetting and related topics understanding and operator is essential for mastering ipv before addressing but don't worry it is actually quite simple to grasp so let's start with and operator the and operator is a Boolean logical operator used in algebra and computer science it only accepts Boolean values as inputs meaning you can't provide decimal numbers as inputs now there are only two bullan values true and false false the end operator accepts only these two Boolean values as inputs and the result of an and operation is always either true or false it is important to remember that the Boolean value true is commonly represented by one and false is represented by zero in computer science this means you can use one instead of true and zero instead of false in most cases now let's understand how the end operator works we need to provide two bullion values or inputs to the end operator then it gives an output that is either true or false here I have three columns input one and two the end operator requires two inputs or Boolean values then the third column is going to display the output or result of the end operation now I have inclosed one and zero in Brackets because true and one are equivalent in Boolean logic and zero and false are also synonymous or same so don't get confused here the first expression is true and false or one and zero it evaluates to false the result is false then we have false and true the result is also false the false and true also so evaluates to false now we have the last combination true and true or one and one now if we apply the end operator to these two True Values the output will be true so the only time the result of the and operation is true when both values or inputs are true so remember this important Point only true and true result in true in and operator all other combinations result in false so that's all about and operator with two Boolean values you can only have four possible combinations of inputs true and true true and false false and true and false and false now let's talk about the logical or operator while not as important for ipv4 addressing as the end operator understanding it is still crucial in some ways it functions similarly to and operator once again I have three columns input a b and the result this time we will be using or operator unlike and which produces a True Result only if both inputs are true the or operator produces a false result only when both inputs are false the first expression that we have true or false or 0 or zero the result is true because at least one of the operant is true now false or true is also true and true or true is also evaluated as true however the r operator produces a false output only when both inputs are false this means that if one oper end or input is true the result is always true this is the important important distinction between the or and and operators all other combinations of inputs will result in a true output except for false and false so to summarize and operator produces true in its output when both inputs or operants are true and the or operator produces false as its output only when both inputs are false that's all you need to know about these two op PR