Chapter 2 Communication of 9618 A Level Computer Science

Chapter 2 Communication of 9618 A Level Computer Science syllabus.

1. 2.1 NETWORKING DEVICES Moshikur Rahman

2. Networking devices are hardware components that link different devices within a network. They play a critical role in managing and directing data as it travels between computers and other devices in a network.

3. ROUTER A router is a key device in a network that connects different networks together. It’s like a traffic manager, making sure data goes where it needs to go. In a typical home or office setup, the router connects your local network to the internet. FUNCTION OF ROUTERS Connecting Networks: Primary Role: The main job of a router is to connect different networks. For example, it links your home network to the internet. Without a router, your devices wouldn’t be able to access websites or online services. Routing Data Packets: Data Management: Routers decide the best path for data to take to reach its destination. When you send a request to visit a website, the router figures out how to get that data from the internet to your device. Network Address Translation (NAT): IP Address Management: Routers use a process called Network Address Translation (NAT) to allow multiple devices on your network to share one public IP address. This is important because it makes your network more efficient and helps protect your devices from direct exposure to the internet. Providing Security: Firewall: Many routers include a basic firewall to help protect your network from unauthorized access. This means it can block certain types of unwanted traffic from entering your network. Assigning IP Addresses (DHCP): Automatic IP Assignment: Routers can automatically assign IP addresses to devices on your network using a system called DHCP. This makes it easier to connect new devices to your network without manual configuration.

4. Switch A switch is a device used in computer networks to connect multiple devices, such as computers, printers, or servers, within a Local Area Network (LAN). Imagine a switch as a traffic controller at a busy intersection. When data (like a message or a file) is sent from one device, the switch decides which path (or lane) the data should take to reach its destination. It does this by looking at the unique address (called a MAC address) of the devices in the network. The switch keeps a list of these addresses and knows exactly where to send the data, making sure it only goes to the right device, not to everyone on the network. This helps make the network faster and more efficient because only the intended device receives the data, unlike in older systems where data would be sent to all devices.

5. Network Interface Card (NIC) A hardware component that allows a computer or device to connect to a network, such as a Local Area Network (LAN) or the internet. It acts as an interface between the device and the network, enabling the device to send and receive data. Key points about a NIC: Physical Connection : It can connect to the network through wired (Ethernet cable) or wireless (Wi-Fi) methods. Unique Identifier : Each NIC has a unique MAC (Media Access Control) address that identifies the device on the network. Role : It converts data from the computer into a format that can be transmitted over the network and vice versa. In short, a NIC is essential for a device to communicate with other devices on a network.

6. Wireless Access Point (WAP) A Wireless Access Point (WAP) is a device that lets your wireless gadgets, like phones and laptops, connect to the internet without needing a cable. Think of it as a Wi-Fi hotspot. It takes the internet signal from your wired network and makes it available for wireless devices. WAPs can act as stand-alone devices or as components of a router, and they can be physically connected to a router or integrated into it.

7. Modem A modem is a device that connects your home or office network to the internet. It takes the internet signal from your internet service provider (ISP) and converts it into a form that your devices can understand. Modem's Role : It acts as a bridge between the internet and your network. The modem receives the internet signal through a cable (like a phone line or fiber optic cable) and converts it into data that your devices can use. Connection to Router : Often, a modem is connected to a router, which then distributes the internet connection to multiple devices, either through cables or Wi-Fi. In short, a modem is the device that gets the internet into your home or office, and it’s essential for connecting to the web.

8. Modem vs Router Modem Purpose: The modem connects your home or office to the internet. It takes the signal from your Internet Service Provider (ISP) and converts it into data that your devices can understand. Connection: The modem is connected to your ISP’s network through a cable, such as a phone line (for DSL) or a coaxial cable (for cable internet). Function: It allows one device (like a computer or a router) to access the internet Router Purpose: The router takes the internet connection from the modem and shares it with multiple devices in your network, either through Wi-Fi or wired connections. Connection: The router is connected to the modem, and then it distributes the internet connection to all your devices (like computers, smartphones, and tablets). Function: It manages the flow of data between devices on your network and the internet, allowing multiple devices to be online at the same time.

9. In Simple Terms: Modem : Connects you to the internet. Router : Shares that internet connection with all your devices. Example: If you only had a modem, you could connect one device (like a computer) to the internet. If you have both a modem and a router (or a combo device), you can connect multiple devices to the internet at once, both wired and wirelessly.

10. A bridge is a network device that connects two or more network segments, allowing them to function as a single network. It helps in managing traffic and reducing network congestion by controlling the data that passes between the segments. Think of a bridge as a gatekeeper that connects two parts of a network. It decides whether data should pass through to the other side, helping to keep the network organized and running smoothly.

11. A repeater is a simple network device that extends the range of a network by boosting or amplifying the signal. It takes in a weak or low signal from one network segment, strengthens it, and then retransmits it to another segment.

12. TASK [past paper - 9618_w23_qp_11]

13. In computer networks , there are two primary models of communication: the peer-to-peer (P2P) and client-server models. Here’s a brief tutorial on the differences between the two: Peer-to-Peer (P2P) Model Client-Server Model Direct Communication : In P2P, devices, referred to as peers , communicate directly with each other. There is no central server managing the network. Shared Resources : Each peer can act as both a client and a server. They share resources like files, bandwidth, and computing power with other peers. Decentralized Network : P2P is decentralized, meaning there's no single point of control. This can make the system more resilient to failures since no central server exists that could be a single point of failure. Example Use : File-sharing networks like BitTorrent use the P2P model, where pieces of files are exchanged between peers​​. Centralized Communication : In the client-server model, clients (end-user devices) communicate through a central server. The server provides resources, services, and manages the communication between clients. Defined Roles : Clients send requests to the server, which processes these requests and sends back the appropriate response. The server is dedicated to managing resources, ensuring security, and controlling access. Centralized Network : This model is centralized, meaning the server acts as the hub for all network operations. If the server fails, the whole network may go down. Example Use : Websites operate using the client-server model, where a client (web browser) requests data from a web server​.