Network Topology

Network topology refers to the physical or logical arrangement of computers, devices, and communication links in a network that determines how data is transmitted.

Example: Computers connected through a central switch in an office network follow Star topology.

1. Bus Topology

Working: In bus topology, all devices are connected to a single backbone cable. When a device sends data, it travels along the cable and reaches all devices, but only the intended receiver accepts it.

Advantage: Low installation cost and simple structure.

2. Ring Topology

Working: In ring topology, devices are connected in a circular manner. Data moves in one direction from one device to the next until it reaches the destination.

Advantage: No data collision occurs.

3. Star Topology

Working: In star topology, all devices are connected to a central hub or switch. Data sent by a device first goes to the hub, which then forwards it to the destination device.

Advantage: Easy to manage and troubleshoot.

4. Tree Topology

Working: Tree topology uses a hierarchical structure where multiple star networks are connected to a main backbone cable, and data flows from parent nodes to child nodes.

Advantage: Suitable for large and expandable networks.

1. Main Benefit of Broadband Transmission System over Baseband

The main benefit of a broadband transmission system is that it can carry multiple signals simultaneously over the same transmission medium using different frequency bands, whereas baseband transmission can carry only one signal at a time.

Broadband transmission supports higher data capacity, longer distance communication, and is widely used in cable TV, internet, and long-distance networks.

2. Attenuation of Transmission Media

Attenuation is the gradual loss of signal strength as data travels through a transmission medium over a distance. As the signal moves farther, it becomes weaker and may cause data errors.

Attenuation depends on the type of transmission media, distance, and signal frequency, and it is usually measured in decibels (dB).

3. Difference between Twisted Pair, Co-axial Cable and Fiber Optics

OSI vs TCP/IP Model

TCP/IP Layer with protocol

a

Basic Functions Performed at MAC Layer

• Frame Encapsulation: Converts data into frames for transmission.
• MAC Addressing: Uses physical (MAC) addresses to identify devices.
• Error Detection: Detects transmission errors using CRC.
• Medium Access Control: Controls access to the shared transmission medium.
• Collision Handling: Manages data collision in shared networks.
• Frame Synchronization: Identifies start and end of data frames.

Diagram of LAN including network Firewall:

Importance of Firewall in Network Security

A firewall is a security system that acts as a barrier between a trusted internal network and the untrusted internet. It protects computers and networks from unauthorized access and cyber threats.

1. Monitors Network Traffic: Firewalls filter incoming and outgoing traffic based on predefined security rules and help detect suspicious activities.
2. Prevents Virus and Malware: Firewalls block harmful data such as viruses, spyware, and malicious programs before they enter the network.
3. Blocks Hackers: Firewalls prevent unauthorized users from accessing sensitive data and systems.
4. Ensures Privacy: Firewalls protect confidential and personal information by restricting unauthorized connections.

Types of Network Firewalls

1. Packet Filtering Firewall: Works at the network layer and allows or blocks packets based on source address, destination address, and port number.

2. Stateful Inspection Firewall: Tracks active connections and makes filtering decisions based on the connection state.

3. Proxy Firewall (Application Layer Firewall): Operates at the application layer and filters traffic by acting as an intermediary between client and server.

4. Circuit-Level Gateway: Works at the session layer and monitors TCP connections without inspecting packet content.

5. Next-Generation Firewall (NGFW): Provides advanced security features such as intrusion prevention, application control, and user identity management.

Difference between Traditional Firewall and Next-Generation Firewall

1. Difference between Symmetric Encryption and Asymmetric Encryption

2. Examples of Encryption Algorithms

Encryption algorithms are used to convert readable data into an unreadable format to protect confidentiality.

• Symmetric: AES (used in disk encryption), DES, Triple DES, Blowfish
• Asymmetric: RSA (used in secure web communication), ECC, DSA, ElGamal

3. Types of Ciphers in Cryptography

(a) Substitution Cipher: Each character is replaced with another character, for example Caesar cipher.

(b) Transposition Cipher: Characters remain the same but their positions are rearranged.

(c) Block Cipher: Encrypts data in fixed-size blocks, for example AES encrypts 128-bit blocks.

(d) Stream Cipher: Encrypts data one bit or byte at a time, for example RC4.

4. Factors Affecting Cryptographic Strength

• Key Length: Longer keys increase resistance against brute-force attacks.
• Algorithm Complexity: Complex algorithms are harder to break.
• Randomness: High randomness in key generation improves security.
• Resistance to Attacks: Ability to resist brute-force and cryptanalysis attacks.
• Implementation: Weak implementation can break strong algorithms.

(i) Difference between Public IP Address and Private IP Address

(ii) Difference between TLS 1.2 and TLS 1.3

1. Difference between Collision Domain and Broadcast Domain

Explanation: Collision domain is related to data collision, while broadcast domain is related to broadcast message distribution.

2. Function of DNS

DNS (Domain Name System) converts human-readable domain names into IP addresses so that computers can locate and communicate with each other on a network.

Example: DNS converts www.google.com into an IP address like 142.250.190.14.

3. Function of DHCP

DHCP (Dynamic Host Configuration Protocol) automatically assigns IP address and network configuration parameters to devices in a network.

Example: When a computer connects to Wi-Fi, DHCP assigns it an IP address automatically.

1. Do we prefer Packet Switching over Circuit Switching?

Yes, in most modern communication networks packet switching is preferred over circuit switching because it uses network resources more efficiently and supports many users at the same time.

Why Packet Switching is Preferred (Reasons)

• Efficient Bandwidth Use: No dedicated path is reserved, so bandwidth is shared and not wasted when a user is idle.
• Better for Burst Traffic: Internet data is usually bursty (not continuous), and packet switching handles this well.
• Scalability: Works efficiently for large networks like the Internet.
• Reliability: If one route fails, packets can take alternative routes.
• Cost Effective: Shared infrastructure reduces overall cost.

2. How Packet Switching Works (Step by Step)

• Step 1: The sender’s message is divided into small units called packets.
• Step 2: Each packet gets a header containing source address, destination address, sequence number, and error-check info.
• Step 3: Packets are sent into the network and travel through routers and switches.
• Step 4: Each router reads the destination address and forwards the packet to the next best route (routing decision).
• Step 5: Packets may take different paths and may arrive out of order due to congestion or routing changes.
• Step 6: At the receiver side, packets are checked for errors, arranged by sequence number, and reassembled into the original message.
• Step 7: If any packet is missing or corrupted, it is retransmitted (common in reliable protocols like TCP).

3. Applications that Use Packet Switching

• Internet browsing: HTTP/HTTPS (websites)
• Email services: SMTP, IMAP, POP3
• File transfer: FTP, SFTP, cloud file sharing
• Video streaming: YouTube, Netflix, IPTV
• VoIP and video calls: WhatsApp call, Zoom, Google Meet (packet-based voice/video)
• Online gaming: Multiplayer games over the Internet
• Messaging apps: WhatsApp, Messenger, Telegram

1. Subnet and Subnet Mask

Subnet: A subnet is a smaller logical division of a large IP network created to improve network management, performance, and security.

Subnet Mask: A subnet mask is a 32-bit number used to identify the network portion and the host portion of an IP address.

2. Subnet Calculation for Network 172.16.0.0/19

The IP address 172.16.0.0 belongs to Class B, whose default subnet mask is /16.

Given subnet mask is /19, so additional bits used for subnetting = 19 − 16 = 3 bits.

Number of Subnets:

Number of subnets = 2³ = 8 subnets.

Number of Hosts per Subnet:

Host bits = 32 − 19 = 13 bits.

Number of hosts per subnet = 2¹³ − 2 = 8190 hosts.

3. Function of OSPF

OSPF (Open Shortest Path First) is a link-state routing protocol used to find the shortest path for data transmission within an IP network.

• Uses cost-based shortest path algorithm (Dijkstra)
• Supports fast convergence
• Scales well for large networks
• Uses area-based routing for efficiency

Conversion of IP Address (192.168.101.5) into Binary:

Decimal IP: 192.168.101.5

Binary IP: 11000000.10101000.01100101.00000101

Key Hardware Components of a Typical Server

A server is a powerful computer designed to provide services, resources, and data to multiple users or systems. Its performance and reliability depend on several critical hardware components.

1. Central Processing Unit (CPU)

The CPU is the brain of the server. It processes instructions, performs calculations, and handles multiple tasks simultaneously. Servers often use multi-core CPUs to support heavy workloads.

2. Random Access Memory (RAM)

RAM temporarily stores data and instructions that the CPU needs quickly. Larger RAM capacity improves multitasking and speeds up application performance.

3. Storage Devices (HDD/SSD)

Storage devices store the operating system, applications, and data. SSDs provide faster data access and better performance compared to traditional HDDs.

4. Motherboard

The motherboard connects all hardware components together. It determines compatibility, expansion capability, and overall system stability.

5. Network Interface Card (NIC)

The NIC enables the server to communicate with other computers and networks. High-speed NICs improve data transfer and network performance.

6. Power Supply Unit (PSU)

The PSU supplies stable and continuous power to the server. Redundant power supplies are often used to ensure high availability.

7. Cooling System

Cooling components such as fans and heat sinks prevent overheating and ensure reliable server operation.

Contribution to Performance and Functionality

High-performance CPUs, sufficient RAM, fast storage, reliable networking, and proper cooling work together to deliver fast processing, high availability, scalability, and long-term reliability.

Difference between Data Backup and Data Recovery

In data management, data backup and data recovery are two closely related but different concepts used to protect and restore data.

1. Data Backup

Data backup is the process of creating and storing copies of data in a separate location so that the data can be used later if the original data is lost or damaged.

Real-World Example: A bank performs daily backups of customer transaction data to a cloud storage system to protect against accidental deletion or hardware failure.

2. Data Recovery

Data recovery is the process of restoring lost, corrupted, or deleted data from backup files or damaged storage devices after a failure or disaster occurs.

Real-World Example: After a ransomware attack encrypts files on a company server, the IT team restores the data from the most recent backup.

Key Differences between Data Backup and Data Recovery

Server Maintenance Best Practices

Server maintenance refers to regular activities performed to keep servers secure, reliable, and efficient. Proper maintenance ensures uninterrupted services and long server life.

1. Routine Cleaning and Hardware Maintenance

Physical cleaning of servers helps remove dust from fans, vents, and hardware components. Dust can cause overheating and hardware failure if not removed regularly.

2. System Monitoring

Continuous monitoring of CPU usage, memory, disk space, and network traffic helps detect performance issues early. Monitoring tools generate alerts for abnormal conditions.

3. Applying Security Patches and Updates

Regularly installing operating system and application security patches protects servers from vulnerabilities, malware, and cyber attacks.

4. Backup and Recovery Management

Frequent data backups ensure that critical data can be restored in case of system failure, data corruption, or cyber incidents.

5. Log Management and Auditing

Reviewing system and security logs helps identify unauthorized access attempts, errors, and unusual activities.

Contribution to Server Longevity and Performance

Regular maintenance prevents hardware damage, reduces downtime, improves system efficiency, enhances security, and ensures consistent server performance over time.

Factors Affecting the Speed of a CPU

The speed of a CPU determines how fast a computer can process instructions. Several hardware and architectural factors influence CPU speed.

1. Clock Speed

Clock speed, measured in GHz, indicates how many cycles a CPU can perform per second. Higher clock speed generally means faster processing.

2. Number of Cores

Modern CPUs have multiple cores, allowing them to execute multiple tasks simultaneously. More cores improve multitasking and performance.

3. Cache Memory

Cache memory stores frequently used data close to the CPU. Larger cache size reduces access time and increases processing speed.

4. Word Length

Word length refers to the number of bits a CPU can process at a time. A 64-bit CPU can handle more data than a 32-bit CPU.

5. Bus Speed

Bus speed determines how fast data is transferred between the CPU, memory, and other components. Higher bus speed improves overall performance.

6. CPU Architecture

Efficient architecture, such as pipelining and instruction-level parallelism, allows the CPU to execute instructions faster.

Program Output (Assume input n = 6)

The program prints the Fibonacci series up to n terms.

Input: Enter the number of terms for the fibonacci series: 6

Output: Fibonacci Series: 0, 1, 1, 2, 3, 5

Explanation of the Program:

The program first takes an integer n as input. It initializes the first two Fibonacci numbers as 0 and 1.

If n is greater than 1, it prints the first number (0). If n is greater than 2, it prints the second number (1).

Then a loop runs from i = 2 to i < n, where each next Fibonacci number is calculated by adding the previous two numbers and printed.

Time Complexity:

The loop runs (n − 2) times, so the time complexity is O(n).

Space Complexity:

The program uses a constant number of variables, so the space complexity is O(1).

Explanation of SQL Query Clauses

SELECT Clause: The SELECT clause specifies which columns or calculated values will appear in the result.

• department_name selects the department name from the departments table.
• AVG(salary) AS average_salary calculates the average salary of selected employees and renames it as average_salary.

FROM Clause: The FROM clause specifies the tables used in the query.

• employees e selects the employees table with alias e.
• JOIN departments d ON e.department_id = d.department_id joins employees with departments using department_id.

WHERE Clause: The WHERE clause filters rows before grouping.

• salary > (SELECT AVG(salary) FROM employees WHERE department_id = d.department_id) selects employees whose salary is greater than the average salary of their department.

GROUP BY Clause: The GROUP BY clause groups rows to perform aggregate calculations.

• GROUP BY department_name groups employees by department name.

HAVING Clause: The HAVING clause filters groups after aggregation.

• HAVING COUNT(*) > 2 selects only departments with more than two qualifying employees.

ORDER BY Clause: The ORDER BY clause sorts the final result.

• ORDER BY average_salary DESC sorts departments by average salary in descending order.