Understanding Computer Networks

• Computer networks are sets of interconnected devices enabling communication
• Achieved through combined hardware and software
• Facilitates resource sharing, data exchange, and communication

Network Types Based on Size and Geography

• Personal Area Network (PAN) serves one person, like a Bluetooth headset connected to a phone
• Local Area Network (LAN) operates in a limited area like a home, school, or office
• Metropolitan Area Network (MAN) spans a city or metropolitan area
• Wide Area Network (WAN) covers expansive areas, even globally, such as the Internet

Network Topologies

• Bus Topology connects devices along a single cable, but is disrupted if the cable breaks
• Ring Topology connects devices in a circle, with data traveling in one direction
• Star Topology connects devices to a central hub/switch; easy to manage, but hub failure disrupts the network
• Mesh Topology has highly interconnected devices, is fault-tolerant but costly
• Tree Topology has a hierarchical structure, combining star and bus topologies

Network Devices

• Hubs broadcast data to all connected devices
• Switches forward data only to the intended recipient
• Routers connect different networks and forward data based on IP addresses
• Bridges connect two LANs, filtering traffic based on MAC addresses
• Modems modulate/demodulate signals for transmission over telephone lines
• Wireless Access Points (WAP) allow wireless connections to a network

The OSI Model

• Open Systems Interconnection (OSI) model is a conceptual framework for network communication
• Consists of seven layers:
  • Physical Layer: Transmits raw bit stream over physical medium
  • Data Link Layer: Formats data for transmission, uses MAC addresses
  • Network Layer: Handles routing via IP addresses
  • Transport Layer: Provides reliable data transfer using TCP and UDP protocols
  • Session Layer: Manages connections between applications
  • Presentation Layer: Handles data formatting and encryption
  • Application Layer: Provides network services like HTTP and SMTP

TCP/IP Model

• Transmission Control Protocol/Internet Protocol (TCP/IP) model is used in the Internet
• Consists of four layers:
  • Link Layer: Combines physical and data link layers; handles hardware
  • Internet Layer: Corresponds to network layer; uses IP for addressing/routing
  • Transport Layer: Uses TCP and UDP protocols
  • Application Layer: Combines session, presentation, and application layers for application services

IP Addressing

• IPv4 uses 32-bit addresses, with a limited address space
• IPv6 uses 128-bit addresses, increasing the address space

Network Protocols

• TCP (Transmission Control Protocol): connection-oriented, reliable data transfer
• UDP (User Datagram Protocol): connectionless, faster, less reliable data transfer
• HTTP (Hypertext Transfer Protocol): for web browsing
• HTTPS (HTTP Secure): secure web browsing
• SMTP (Simple Mail Transfer Protocol): sends email
• POP3 (Post Office Protocol version 3): receives email
• IMAP (Internet Message Access Protocol): manages email on a server
• DNS (Domain Name System): translates domain names to IP addresses
• DHCP (Dynamic Host Configuration Protocol): assigns IP addresses automatically
• FTP (File Transfer Protocol): transfers files

Network Security

• Firewalls control network access
• Encryption prevents unauthorized access
• VPN (Virtual Private Network) creates secure connections over public networks
• Intrusion Detection Systems (IDS) monitor for suspicious activity
• Intrusion Prevention Systems (IPS) actively block malicious traffic
• Authentication verifies user/device identity
• Access Control restricts access to network resources

Network Performance

• Bandwidth is the data transfer rate (bits per second)
• Throughput is the actual rate of successful data delivery
• Latency is the data transfer delay
• Jitter is the variation in latency
• Packet Loss is the percentage of packets not reaching the destination

Wireless Networking

• Wi-Fi (Wireless Fidelity) uses radio waves for network connectivity
• Bluetooth enables short-range wireless communication
• Cellular Networks provide mobile communication networks

Cloud Networking

• Cloud networking involves virtualized network infrastructure over the internet
• It enables scalable and flexible network resources
• Services include virtual networks, load balancing, and network security

Network Management

• SNMP (Simple Network Management Protocol) monitors/manages network devices
• Network monitoring tools track performance and identify issues
• Configuration management sets up and maintains network devices

Subnetting

• Subnetting divides a network into smaller subnetworks
• Improves network organization, security, and performance
• Subnet masks define network and host portions of IP addresses

Network Address Translation (NAT)

• NAT translates private IP addresses to public IP addresses
• Multiple private network devices can share a single public IP address
• Provides security by hiding internal IP addresses

Virtual LANs (VLANs)

• VLANs logically separate network segments
• Enhances security, network management, and performance
• Devices in different VLANs cannot communicate directly without routing

Quality of Service (QoS)

• QoS prioritizes network traffic
• Ensures critical applications receive sufficient bandwidth and low latency
• Implemented through traffic shaping, queuing, and resource reservation

Network Convergence

• Network convergence integrates voice, video, and data services
• It reduces infrastructure costs and simplifies network management
• Requires robust network infrastructure and QoS mechanisms

Software Defined Networking (SDN)

• SDN separates the control plane from the data plane
• Allows centralized control and programmability
• Enables dynamic network configuration and optimization

Network Function Virtualization (NFV)

• NFV virtualizes network functions such as firewalls and load balancers
• Runs network functions on standard hardware or virtual machines
• Increases network agility and reduces hardware costs

Content Delivery Networks (CDNs)

• CDNs cache content closer to users through distributed servers
• Improves website performance and reduces latency
• Used for delivering web content, video streaming, and software updates

Border Gateway Protocol (BGP)

• BGP exchanges routing information between autonomous systems
• Enables inter-domain routing to determine the best path for data transmission
• Is critical for the functioning of the global Internet

Network Troubleshooting

• A systematic approach to identifying and resolving network problems
• Includes checking physical connections, configurations, and device status
• Uses tools like ping, traceroute, and network analyzers

Future Trends in Computer Networks

• 5G and beyond will see faster wireless communication with lower latency
• The Internet of Things (IoT) will connect vast numbers of devices to the Internet
• Edge Computing processes data closer to the network edge
• Artificial Intelligence (AI) in networking will enable automated network management and optimization