Computer Networks: Intro and Components

Introduction to Computer Networks

• A computer network involves a group of devices connected via transmission media like wires or cables.
• The purpose of a computer network is to send and receive data stored on other devices in the network.
• The devices are often called nodes and can include computers, printers, scanners, and fax machines.

Basic Components

• Five basic components form a computer network: message, sender, receiver, transmission media, and protocol.
• Message: The data or information to be transferred from one device to another over a network
• Sender: the device that has data and needs to send it to another device connected to the network.
• Receiver: the device expecting data from the sender device on the network.
• Transmission media: Necessary for transferring data between devices, including options like wires, cables, and radio waves.
  • Examples: Twisted Pair Cables, Optical Fiber Cables, Radio Frequency
• Protocol: a set of rules agreed upon by sender and receiver.
  • Necessary for communication between connected devices.
  • HTTP and HTTPS are used by web browsers, and SMTP is used by email services.

Network Functionality

• The basic building blocks of a computer network include nodes and links.
• Network nodes include equipment for data communication like modems and routers, or equipment of a data terminal like connecting 2+ computers.
• Links can be wires, cables, or free space in the case of wireless.
• Networks operate based on protocols that direct sending and receiving data via links.
• An IP address on each device helps identify each device within the network.

Basic Terminologies

• Network: a collection of computers and devices connected to enable communication and data exchange.
• Nodes: devices that are connected to such a network.
  • These include computers, servers, printers, routers and switches.
• Hub: a hardware device that divides the network connection among multiple devices by broadcasting the request to all devices as part of the entire network
  • Devices that a request does not belong to will drop it.
• Switch: a hardware device connecting multiple devices on a computer network but contains more advanced features than a hub.
  • The switch contains an updated table that decides where the data is transmitted or not.
  • Physical addresses present in the switch are used to deliver the message to the correct destination based on the message.
  • A switch does broadcasts a message to the entire network like a hub, determining the specific destination device.
  • Switches provide a direct connection between source/destination, while increasing network speeds.
• Router: a hardware device used connect a LAN with an internet connection,
  • Routers receive, analyze, and forward incoming packets to other networks
  • Routers work in Layer 3 (Network layer) of the OSI Reference Model.
  • Routers forward packets based on information available in the routing table, using the best path available.
• Protocol: a set of rules and standards governing how data is transmitted over a network.
  • Examples include TCP/IP, HTTP, and FTP.
• Topology: refers to the physical and logical arrangement of nodes on a network.
  • Common topologies include bus, star, ring, mesh, and tree structures.
• IP Address: a unique numerical identifier for every device on a network.
  • Needed to identify & enable communication between devices.
  • IP addresses can be public or private.
• DNS (Domain Name System): a protocol translating human-readable domain addresses (like google.com) to IP addresses.
  • Think of it as the Internet's Phonebook.
• Firewall: monitors incoming/outgoing network traffic and allows or blocks specific traffic based on security rules.
  • Protects networks from unauthorized access/threats.

Features of Computer Networks

• Performance: Measured by response time, which should be minimal when sending and receiving data from one node to another.
• Data Sharing: Facilitates sharing data between different systems connected through a transmission medium.
• Backup: Central server should maintain backups of shareable data.
  • Important so that in case of failure, data can be recovered faster.
• Reliability: Networks should typically not fail, and have fast recovery.
• Security: Secure networks keep data safe from unauthorized access
  • The sent data should be received at receiving node; no data should be lost during transmission. -Scalability: Networks should allow scaling by adding new computers (or nodes) to a network.
  • For example: If a company runs 100 computer LAN for 100 employees, then it should be able to scale by adding computers when hiring an additional 100 employees.
• Software and Hardware Compatibility: Networks should limit computer usage to same hardware and software; and better compatibility between different software and hardware configurations.

Types of Networks

• Various network types are distinguished by geographical area coverage, from smallest to largest:
  • Personal Area Network (PAN): supports a personal or separate workspace under 10 meters, used to connect tables, smartphones, and laptops.
  • Local Area Network (LAN): connects devices within a few kilometers, offices, companies, factories use LANs to exchange data and information
  • Metropolitan Area Network (MAN): covers a larger area than LAN, small area compared to a WAN.
    • Covers range of 5-50km, speeds in terms of Mbps.
    • Connects computers apart, residing in the same/different cities.
    • Serves as an ISP for customers who need high-speed connectivity.
  • Wide Area Network (WAN): a vast geological range covering a country or continent.
    • Used in military service, mobile operations, in railways and airlines reservations.

Learn about computer networks, which consist of interconnected devices for data exchange. Key components include the message, sender, receiver, transmission media like cables or radio waves, and the protocol. Essential for understanding network functionality.