Computer Networks Revision Sheet PDF

Revision sheet Computer Networks Computer network: a group of computers and other devices connected, allows sharing of data and information. Benefits of computer networks: Communication: Computer networks allow devices to send and receive data. Wor...

Revision sheet Computer Networks Computer network: a group of computers and other devices connected, allows sharing of data and information. Benefits of computer networks: Communication: Computer networks allow devices to send and receive data. Work from anywhere: computer networks allow users to work online anywhere. Share resources: The computer network allows the users to share software and hardware. Network Hardware includes all devices used to create networks, whether computers or devices used to connect other devices. Network hardware types: The network interface card (NIC): each NIC has a unique identifier called a MAC address. End devices or host: computers used to send or receive data. Switch: used to connect end devices to a LAN Router: is needed to send packets from one LAN to another Network types: expressed by the geographic area and number of computers PAN (Personal Area Network) A Personal Area Network(PAN) is a computer network formed around a person. It generally contains a computer, mobile device, or personal digital assistant. LAN (Local Area Network) A Local Area Network (LAN) is a group of computers and peripheral devices connected in a limited area such as a school, laboratory, home, or office building. LAN is created when the end-devices connected. MAN (Metropolitan Area Network) A Metropolitan Area Network or MAN is consisting of a computer network across an entire city, college campus, or a small region. This type of network is larger than LAN, which is mostly limited to a single building or site. WAN (Wide Area Network) Wide Area Network(WAN) is another important computer network that is spread across a large geographical area. WAN network system could be a connection of a LAN which connects with other LAN’s using telephone lines and radio waves.  Network type Advantages Disadvantages PAN PAN networks are relatively secure It may establish a bad connection to and safe other networks at the same radio bands. Distance limits. LAN You can easily transfer data and LAN will save the cost of shared messages over networked computer resources, but the initial computers. cost of installing Local Area It will be easy to manage data in Networks is quite high. one place to make data more The LAN admin can check the secure. personal data files of every LAN Local Area Network offers the user, so it does not offer good facility to share a single internet privacy. connection among all the LAN Local Area Network requires a users. constant LAN administration as there are issues related to software setup and hardware failures WAN WAN helps you to cover a larger The initial setup cost of investment geographical area. Therefore is very high. business offices situated at longer It is difficult to maintain the WAN distances can easily communicate. network. You need skilled technicians and network administrators. It requires more time to resolve issues because of the involvement of multiple wired and wireless technologies. Network topology: describe the methods of a network mapped. This type of network is larger than LAN, which is mostly limited to a single building or site. The topology term refers to both the physical and logical layout of a network. Types of Network topologies: P2P Topology: Point-to-point topology is the easiest of all the network topologies. In this method, the network consists of a direct link between two computers. Bus Topology: Bus topology uses a single cable which connects all the included nodes. The main cable acts as a spine for the entire network. Ring Topology: In this topology, every computer is connected to another computer. Here, the last node is combined with the first one. Star Topology: all the computers connect with the help of a hub. This cable is called a central node, and all other nodes are connected using this central node. It is most popular on LAN networks as they are inexpensive and easy to install. Topology Advantages Disadvantages P2P This is faster and highly The biggest drawback is reliable than other types of that it only be used for connections since there is a small areas where direct connection. computers are in close Does not need an proximity. expensive server as You can’t back up files and individual workstations are folders centrally used to access the files Bus The cost of the cable is low In case if the common cable compared to other fails, then the entire system topologies, so it is widely will crash down. used to build small When network traffic is networks. heavy, it develops collisions Famous for LAN networks in the network. because they are Cables are always of a inexpensive and easy to limited length. install. It is widely used when a network installation is small, simple, or temporary. Ring Adding or deleting a device A break in a single ring can in-ring topology needs you risk the breaking of the to move only two entire network. connections. Adding or removing the The troubleshooting computers can disturb the process is difficult in a ring network activity topology. Failure of one computer can disturb the whole network Star Easy to troubleshoot, set If the hub or concentrator up, and modify. fails, attached nodes are Only those nodes are disabled. affected, that has failed. Cost of installation of star Other nodes still work. topology is costly. Fast performance with few A damaged cable or lack of nodes and very low proper termination may network traffic. bring the network down In Star topology, addition, deletion, and moving of the devices are easy. How to select a network topology? For networks with Bluetooth, we use P2P Bus topology is surely the least expensive to install a network. For Wi-fi networks, use Star topology.  Ring topology can be use with servers. Network protocols: an established set of rules that determine how data is transmitted between different devices in the same network. Essentially, it allows connected devices to communicate with each other, regardless of any differences in their internal processes, structure, or design. Types of Network Protocols: Internet Protocol( IP): a numerical label assigned to the devices connected to a computer network that uses the IP for communication. o IP address is an identifier for a specific machine on a particular network. o An IP address consists of four numbers, each one between 0 and 255, and a single dot (.) separates each number or set of digits. Dynamic Host Configuration Protocol (DHCP): (DHCP) is a client/server protocol that automatically provides an Internet Protocol (IP) host with its IP address Domain Name System(DNS): it is the phonebook of the Internet, it connects the IP address with the domain name. such as 129.234.122.1 connected to www.example.com. Importance of IP: An IP address is used to locate computers over the network. Because of the increased number of internet users IP moved from IPv4 to IPv6. Importance of DHCP: it makes IP management easier since assigning an IP to a device when joining the network is automated. Transfer data over a network 1. The file you want to transfer is broken up into units of data called packets. 2. The Packets are then put on the network medium and sent over the network. Data transfer rate(Bandwidth): Bandwidth is the number of bits that pass through the network in one second. Data transfer rate measurements: bits per second (bps). kilobits per second (kbps) = 1000 bps. megabits per second (Mbps) = 1000 000 bps. gigabits per second (Gbps) = 1000 000 000 bps. Transmitting and receiving data: 1. Half-duplex transmission a. Half-duplex data transmission is where only one computer transmits data at any time.  2. Full-duplex transmission a. transmit and receive at the same time. b. transmit and receive data even faster. Computer Network security Host level Host is the end device used by the user. Protect the device over a network to increase network security. How to protect the host: Limited access: only authorized people can use the device. Lock devices by password: only authorized people can log in to the device. Different levels of authority: not all users can access the same resources. Protect each device: use a method such as anti-virus to protect each device. Network level Network is the connected devices whether it is on LAN or WAN. Protect network: Divide the network into internal access and all access. The internal access network should be limited to use inside the building and has no access from outside. The network uses the Firewall program to protect the network. All main devices such as routers should be locked and limited access. Secure the network using strong passwords. User level Users are the persons who have the right to use and access the network.  Protect user: Use a strong password to protect your account. Use an official application from a known source. Don’t share your account information. Don’t share your personal information over the network or social media. Use anti-virus to protect your device. Use secure websites. Strong password contains all of the following. Has 8 characters in length at least. Contains letters, numbers, and special characters. Does not have any personal information. Use secure websites. We can differentiate between secure websites and nonsecure by The “https” and “http” protocols used to create the website. The https is the secure form of http DATA AND INFORMATION Data is simply facts or raw information that we collect. Think of it as a collection of numbers or words that don’t make much sense by themselves. Data is not very helpful until we organize it and give it meaning. Types of data 1. Quantitative Data: This is data we can count or measure. It always uses numbers. 2. Qualitative Data: This is descriptive data that tells us about qualities or characteristics. It’s usually words, not numbers. Information is what we get when we organize data to make it meaningful. It’s the answer or insight we gain after analyzing the data Data is unorganized. It’s just facts or Information is organized and numbers. meaningful. It helps us answer questions. Data representation is when we take data and turn it into a visual format— like a chart or graph—to make it easier to understand LINE GRAPH: best for quantitative data Shows trends over time DOT PLOT best for quantitative data Counts how many times data occurs (frequency) BOX & WHISKER PLOT best for quantitative data Can use more than one to compare data on the same graph Bar chart best for quantitative data Counts how many times data occurs between set ranges(such as students marks) Pai chart best for qualitative data Counts the percentage of data related to each other.