Computer Networks Cheatsheet - Part 2
THINESH BABU KS
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Computer Networks Cheatsheet - Part 2

1. Network Security

1.1 Security Goals

  • Confidentiality: Ensuring that information is not accessed by unauthorized individuals.
  • Integrity: Maintaining the accuracy and completeness of data.
  • Availability: Ensuring that information and resources are available to authorized users when needed.

1.2 Common Threats

  • Malware: Malicious software such as viruses, worms, and trojans.
  • Phishing: Fraudulent attempts to obtain sensitive information by pretending to be a trustworthy entity.
  • Man-in-the-Middle Attack: Intercepting and altering communication between two parties.
  • Denial of Service (DoS): Overloading a system with traffic to make it unavailable to users.

1.3 Security Measures

  • Firewalls: Monitor and control incoming and outgoing network traffic based on predetermined security rules.
  • Encryption: Protects data by converting it into a code to prevent unauthorized access.
  • Antivirus Software: Detects and removes malicious software.
  • Intrusion Detection Systems (IDS): Monitors network traffic for suspicious activity.

2. Network Layer Protocols

2.1 IP (Internet Protocol)

  • IPv4: The fourth version of the IP, which uses 32-bit addresses.
  • IPv6: The sixth version of the IP, which uses 128-bit addresses.

2.2 ICMP (Internet Control Message Protocol)

Used for error messages and operational information queries. Example: Ping command.

2.3 ARP (Address Resolution Protocol)

Translates IP addresses to MAC (Media Access Control) addresses.

2.4 RARP (Reverse Address Resolution Protocol)

Translates MAC addresses to IP addresses.

3. Transport Layer Protocols

3.1 TCP (Transmission Control Protocol)

A reliable, connection-oriented protocol that ensures the complete transfer of data. It provides error checking and guarantees the delivery of packets in the correct order.

3.2 UDP (User Datagram Protocol)

A connectionless protocol that does not guarantee delivery or order, making it faster and more efficient for certain applications like streaming.

4. Wireless Networks

4.1 Wi-Fi (Wireless Fidelity)

Allows devices to connect to a network wirelessly within a certain range.

4.2 Bluetooth

A short-range wireless technology for exchanging data between fixed and mobile devices.

4.3 Cellular Networks

  • 2G/3G/4G/5G: Generations of mobile network technology, with increasing speeds and capabilities.

4.4 Ad Hoc Networks

A type of wireless network where devices communicate directly without a central access point.

5. Network Address Translation (NAT)

5.1 Definition

NAT is a method used to map multiple private IP addresses to a single public IP address, allowing multiple devices on a local network to share a single public IP.

5.2 Types

  • Static NAT: One-to-one mapping between local and public IP addresses.
  • Dynamic NAT: Maps private IP addresses to a pool of public IP addresses.
  • PAT (Port Address Translation): Maps multiple private IP addresses to a single public IP address using different ports.

6. Network Management

6.1 SNMP (Simple Network Management Protocol)

Used for managing devices on IP networks. It provides a way for network devices to communicate information about their status and performance.

6.2 Network Monitoring Tools

  • Wireshark: A network protocol analyzer that captures and displays data packets.
  • Nagios: An open-source tool for monitoring network resources.
  • SolarWinds: A suite of network management tools.

7. Virtual Private Network (VPN)

7.1 Definition

A VPN creates a secure, encrypted connection over a less secure network, such as the internet, to provide remote access to a private network.

7.2 Types

  • Remote Access VPN: Allows users to connect to a private network from a remote location.
  • Site-to-Site VPN: Connects entire networks to each other over the internet.

8. Quality of Service (QoS)

8.1 Definition

QoS refers to the management of network resources to ensure the performance of critical applications.

8.2 Techniques

  • Traffic Shaping: Controlling the volume of traffic being sent into a network.
  • Prioritization: Assigning priority levels to different types of traffic.
  • Bandwidth Allocation: Allocating specific amounts of bandwidth to different types of traffic.

9. Cloud Computing

9.1 Definition

Cloud computing delivers computing services (servers, storage, databases, networking, software) over the internet, allowing for flexible resources, rapid innovation, and economies of scale.

9.2 Types of Cloud Services

  • IaaS (Infrastructure as a Service): Provides virtualized computing resources over the internet.
  • PaaS (Platform as a Service): Provides a platform allowing customers to develop, run, and manage applications.
  • SaaS (Software as a Service): Delivers software applications over the internet, on a subscription basis.

9.3 Deployment Models

  • Public Cloud: Services are delivered over the public internet and shared across organizations.
  • Private Cloud: Services are maintained on a private network and used by a single organization.
  • Hybrid Cloud: Combines public and private clouds, allowing data and applications to be shared between them.
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