Computer Networks: An Overview

• The presentation generally covers security and networking concepts for second-year computer science students in the academic year 2024-2025

What are Networks?

• Networks consist of hardware components like computers and their peripherals
• Networks also include software components like operating systems
• Protocols ensure the proper flow of information between these computers.

Computer Networks

• Computer networks are interconnected computers using communication lines for data exchange, resource sharing, and application access
• These networks are managed by specialized software and follow specific agreements or protocols
• A network consists of two or more computers, linked via wired or wireless mediums
• Communication lines provide the connection for data transfer
• Connection describes the process of sending and receiving data
• Shared resources include devices that offer services like printing and faxing

Computer Network Systems

• A computer network system involves connecting two or more computers for data exchange and information sharing
• Peripherals such as printers and scanners can be directly connected using cables
• Cables include coaxial cables, twisted pair cables, or fiber optic cables
• Each computer requires a Network Interface Card (NIC)
• Data can be transmitted via telephone lines if computers are far apart, although this is slower
• Modems or fax cards may be required to convert digital signals to analog signals and vice versa for telephone line communication

Benefits of Computer Networks

• Information sharing is conducted quickly and easily between networked devices
• Shared resources and peripheral devices can be shared within a network
• Centralized management simplifies the administration of shared workspaces
• Large volumes of information can be stored in databases that are indexed and easily accessible
• Immediate communication is facilitated through email and messaging
• Reduced costs stem from the ability to share resources
• Exchanging files is made easy for network users
• Internet access can be provided to users
• E-learning platforms offer simple access to educational resources
• Online communication platforms streamline the process of communication for individuals
• Information is available from diverse sources across different domains

Basic Components of a Network

• Hardware Components: Physical elements of a network
• Desktop and laptop computers serve as workstations for various tasks and application management
• A server is a central device offering network resources and services to other devices
• Routers connect multiple networks and manage data traffic using IP addresses
• Switches connect devices within a local network for efficient data transfer
• Access points expand wireless signal range for devices within the network
• Hubs connect network devices and transmit data to all ports
• Bridges connect two local networks and filter traffic based on MAC addresses
• Repeaters amplify and retransmit network signals to improve coverage over longer distances
• NICs provide wired or wireless connectivity, each with a unique MAC address
• Modems allow internet connection by converting analog signals to digital signals and vice versa

Software Components

• Operating Systems manage network operations and provide user interfaces
• Protocols define the communication rules between devices
• Security Software protects the network from threats and attacks
• Network Software includes tools for network admin, security, data administration, and user permissions
• Network admin tools organize operations and allocate resources for users
• Security establishes network confidentiality and protection
• Data admin organizes databases, prioritizes the use of supplementary devices
• User Access specifies permissions for each user and monitors network operations
• Windows NT and Novell, are examples of programs

Media

• Wired Media includes twisted pair cables that are used in Ethernet networks
• Coaxial cables are usually used in TV networks
• Fiber optic cables are used for extremely high transfer speeds, and use light to transfer data
• Wireless Media uses electromagnetic waves to transmit data
• Wi-Fi, Bluetooth, and infrared tech are all examples of wireless media

Wired vs Wireless Media

• Wired connections transfer data at a limited speed compared to fiber optic cables
• Wireless connections have very high transfer speeds, and can transfer over long distances
• Wired connections are inexpensive and simple to set up
• Wireless connections are specialized and need maintenance
• Wired connections are less safe and prone to eavesdropping and data theft
• Wireless connections have high safety
• Wired is well suited for small local networks,
• Wireless is well suited for networks that work over long distances

Network Topology

• Physical, and logical arrangement of network nodes and connection
• Bus networks are low cost and easy to setup but are less effective with lots of node
• Star networks are are easy to troubleshoot and setup but the performance depends on the performance of the central devices
• Ring networks transmits data well but if one devices fails it compromises the whole network
• Mesh Networks provides coverage, and has high reliability when set up .
• Hybrid networks are also a thing that combines advantages for networks

Network Service Types

• Peer-to-Peer Network pros are Cost-effective and Easy to set up
• Peer-to-Peer Network cons are Less secure with Difficult data admin and has Lesser performance
• Client Servers have High security but there is Central management of resources, they also have Enhanced performance
• Client Servers need High setup and maintenance costs but are reliable with a single point of failure

Network Scope

• Local Area Network (LAN) is within a limited area like a house
• Metropolitan Area Network (MAN) spans across greater geographical areas, such as a city

Network Security Basics

• It employs protocols, configurations, and practices to maintain the trustworthiness, confidentiality, and accessibility of networks and data
• Security measures are key for defending a network and its data
• Firewalls, encryption, intrusion detection, access control, authentication, and security updates are some components for network security
• A main objective of security, is to defend against cyber threats
• Common cyber threats include; viruses, malware, breaches, and coordinated attacks

Network Security Threats

• Includes any deliberate actions or attempts to leverage network vulnerabilities to jeopardise and steal data and disrupt services
• Malware is a malicious software designed to damage targeted networks
• Keyloggers record every keystroke to steal login details or personal information
• Trojan horses are programs that deceive users by concealing malicious plans in seemingly innocent software
• Ransomware locks access to devices or apps and ask a compensation
• Adware are popup advertisement generating software which consumes the system resources
• Spyware secretly collects sensitive data without the user knowing
• Logic Bombs; sets to be activated at certain date
• Phishing; tricks users for the purpose of downloading malwares

Network Troubleshooting

• Identify and fix problems that can affect the network
• Connection can be on the internet
• The steps to find the network are
• Double check all the connected devices
• Double check the cables
• Double check routers
• Restart devices
• Check internet

How to check the internet

• Find Command Prompt in windows
• enter "ping 8.8.8.8"
• If you get back a response then you have connection to internet
• Run "ping" on another computer
• Make you sure have you have enabled the right IP

Some more tools for Network Troubleshooting

• Makesure Router is working
• Check Router connection
• Check Antivirus
• Check Internet Speed
• Use third party network troubleshooting program