Network Fundamentals

• Networks facilitate communication and resource sharing between devices.
• Wireless networking enables devices to connect without physical cables, using radio waves.
• Network security involves protecting network resources and data from unauthorized access or attacks.

Network Fundamentals

• A network is a collection of interconnected devices capable of exchanging data.
• Networks can be classified based on size, such as LAN (Local Area Network), WAN (Wide Area Network), and MAN (Metropolitan Area Network).
• Network architecture can follow client-server or peer-to-peer models.
• Client-server networks have dedicated servers providing resources to clients.
• Peer-to-peer networks allow devices to share resources directly with each other.
• Network topologies describe the layout of connections, including bus, star, ring, and mesh topologies.
• A bus topology uses a single cable for all connections.
• A star topology connects devices to a central hub or switch.
• A ring topology connects devices in a circular path.
• A mesh topology provides redundant paths between devices for high availability.

Wireless Networking Technologies

• Wireless networks use radio waves to transmit data between devices.
• IEEE 802.11 standards define various Wi-Fi protocols, including 802.11a/b/g/n/ac/ax.
• Wi-Fi standards differ in frequency bands (2.4 GHz and 5 GHz), bandwidth, and range.
• Wireless Access Points (APs) serve as central connection points in wireless networks.
• Wireless routers combine the functions of an AP, router, and sometimes a modem.
• Wireless security protocols such as WEP, WPA, and WPA2 protect wireless networks from unauthorized access.
• WEP (Wired Equivalent Privacy) is an older, less secure protocol.
• WPA (Wi-Fi Protected Access) and WPA2 are more secure protocols using stronger encryption methods.
• WPA3 is the latest standard, offering improved security features.
• Bluetooth is a short-range wireless technology for connecting devices like headphones and keyboards.
• Cellular networks (3G, 4G, 5G) provide wide-area wireless connectivity using cell towers.

Network Protocols and Standards

• TCP/IP (Transmission Control Protocol/Internet Protocol) is the foundational protocol suite for the internet.
• IP addresses are unique identifiers assigned to devices on a network.
• IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses.
• Subnet masks define the network and host portions of an IP address.
• DNS (Domain Name System) translates domain names to IP addresses.
• DHCP (Dynamic Host Configuration Protocol) automatically assigns IP addresses to devices.
• HTTP (Hypertext Transfer Protocol) is used for web browsing.
• HTTPS (HTTP Secure) is a secure version of HTTP that uses encryption.
• SMTP (Simple Mail Transfer Protocol) is used for sending email.
• POP3/IMAP are used for receiving email.
• FTP (File Transfer Protocol) is used for transferring files.
• SSH (Secure Shell) is a secure protocol for remote access to systems.

Network Hardware

• Network Interface Cards (NICs) enable devices to connect to a network.
• Routers forward data packets between networks.
• Switches connect devices within a local network.
• Hubs connect devices in a simple star topology (less efficient than switches).
• Modems convert analog signals to digital signals and vice versa for internet access.
• Firewalls protect networks from unauthorized access.
• Cables (Ethernet, fiber optic) are used for wired network connections.
• Ethernet cables include Cat5e, Cat6, and Cat6a.
• Fiber optic cables provide higher bandwidth and longer distances.

Network Security Principles

• Confidentiality ensures that data is accessible only to authorized users.
• Integrity ensures that data is accurate and unaltered.
• Availability ensures that network resources are accessible when needed.
• Authentication verifies the identity of users or devices.
• Authorization determines what resources a user is allowed to access.
• Accounting tracks user activity and resource usage.

Common Network Threats

• Malware includes viruses, worms, Trojans, and ransomware.
• Phishing attacks trick users into revealing sensitive information.
• Denial-of-Service (DoS) attacks overwhelm network resources, making them unavailable.
• Man-in-the-Middle (MitM) attacks intercept communication between two parties.
• SQL injection attacks exploit vulnerabilities in database-driven applications.
• Cross-Site Scripting (XSS) attacks inject malicious scripts into websites.
• Password attacks include brute-force, dictionary, and social engineering techniques.

Network Security Measures

• Firewalls filter network traffic based on predefined rules.
• Intrusion Detection Systems (IDS) monitor network traffic for malicious activity.
• Intrusion Prevention Systems (IPS) automatically block malicious activity.
• Virtual Private Networks (VPNs) create secure connections over public networks.
• Encryption protects data confidentiality by converting it into an unreadable format.
• Access controls restrict access to network resources based on user roles and permissions.
• Security audits assess the effectiveness of security measures.
• Regular software updates and patching address security vulnerabilities.
• Employee training educates users about security threats and best practices.
• Physical security measures protect network hardware from theft or damage.

Wireless Network Security Measures

• Enable WPA3 or WPA2 encryption on wireless routers.
• Use a strong and unique password for the wireless network.
• Change the default SSID (network name) to something less obvious.
• Disable SSID broadcasting to hide the network from casual searches.
• Enable MAC address filtering to restrict access to authorized devices.
• Regularly update the firmware on wireless routers.
• Use a guest network for visitors to isolate them from the main network.
• Monitor the wireless network for unauthorized devices.
• Place the wireless router in a secure location.

Network Troubleshooting

• Start by checking physical connections and power to devices.
• Verify IP addresses and network configurations.
• Use ping to test network connectivity.
• Use traceroute to identify the path packets take to reach a destination.
• Check firewall settings and access control lists.
• Analyze network traffic using packet sniffers like Wireshark.
• Review system logs for error messages.
• Update drivers and firmware on network devices.
• Consult online resources and documentation for troubleshooting tips.

Network Segmentation

• Network segmentation divides a network into smaller, isolated segments.
• Segmentation improves security by limiting the impact of breaches.
• It enhances performance by reducing network congestion.
• VLANs (Virtual LANs) logically separate devices within a physical network.
• Subnetting divides a network into smaller subnets based on IP address ranges.
• Firewalls can be used to control traffic between network segments.
• DMZs (Demilitarized Zones) are used to host publicly accessible services while protecting the internal network.

Cloud Networking

• Cloud networking involves using cloud-based resources to build and manage networks.
• Virtual networks in the cloud allow users to create isolated network environments.
• Cloud-based firewalls provide security for cloud resources.
• Load balancers distribute traffic across multiple servers in the cloud.
• VPN gateways connect on-premises networks to cloud networks.
• Content Delivery Networks (CDNs) cache content closer to users for faster delivery.

Network Monitoring

• Network monitoring tools track network performance and identify issues.
• SNMP (Simple Network Management Protocol) is used to collect information from network devices.
• Network monitoring systems can alert administrators to potential problems.
• Performance metrics include bandwidth utilization, latency, and packet loss.
• Security monitoring tools detect and respond to security threats.
• Log management systems collect and analyze security logs from various sources.
• SIEM (Security Information and Event Management) systems provide a centralized view of security events.