easiest way to remember, Cheat Sheet of Computer science

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Aarya Dalvi
DCN Question Bank
1) Twisted Pair Cable (2 marks)
Twisted pair cable is a type of guided transmission medium in which two insulated copper wires are
twisted together to reduce noise and interference.
โ€ข It is commonly used in telephone lines and LAN networks.
โ€ข It is low cost and easy to install, but has limited bandwidth and distance.
2)Fibre Optic Cable (4 marks)
Fibre optic cable is a transmission medium that uses light signals to transmit data through thin
strands of glass or plastic fibres.
โ€ข It consists of core, cladding, and protective coating.
โ€ข It provides very high speed and large bandwidth for data transmission.
โ€ข It is immune to electromagnetic interference and has low signal loss.
โ€ข It is widely used in internet, cable TV, and long-distance communication.
3) Satellite Transmission (4 marks)
Satellite transmission is a wireless communication method that uses artificial satellites to transmit
signals over long distances.
โ€ข Signals are sent from an earth station (uplink) to the satellite, which then retransmits them
back to another earth station (downlink).
โ€ข It is used for television broadcasting, internet services, GPS, and communication.
โ€ข It covers a large geographical area, making it suitable for global communication.
โ€ข However, it has high cost and signal delay (latency) due to long-distance transmission.
4) Multiplexing (4 marks)
Multiplexing is a technique used to combine multiple signals into a single transmission channel to
improve efficiency.
โ€ข It allows multiple users to share the same communication medium.
โ€ข Types include Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM),
and Wavelength Division Multiplexing (WDM).
โ€ข At the receiver end, the signals are separated using a demultiplexer.
โ€ข It increases bandwidth utilization and reduces communication cost.
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Aarya Dalvi DCN Question Bank

  1. Twisted Pair Cable (2 marks) Twisted pair cable is a type of guided transmission medium in which two insulated copper wires are twisted together to reduce noise and interference.
  • It is commonly used in telephone lines and LAN networks.
  • It is low cost and easy to install , but has limited bandwidth and distance. 2)Fibre Optic Cable (4 marks) Fibre optic cable is a transmission medium that uses light signals to transmit data through thin strands of glass or plastic fibres.
  • It consists of core, cladding, and protective coating.
  • It provides very high speed and large bandwidth for data transmission.
  • It is immune to electromagnetic interference and has low signal loss.
  • It is widely used in internet, cable TV, and long-distance communication.
  1. Satellite Transmission (4 marks) Satellite transmission is a wireless communication method that uses artificial satellites to transmit signals over long distances.
  • Signals are sent from an earth station (uplink) to the satellite, which then retransmits them back to another earth station ( downlink ).
  • It is used for television broadcasting, internet services, GPS, and communication.
  • It covers a large geographical area , making it suitable for global communication.
  • However, it has high cost and signal delay (latency) due to long-distance transmission.
  1. Multiplexing (4 marks) Multiplexing is a technique used to combine multiple signals into a single transmission channel to improve efficiency.
  • It allows multiple users to share the same communication medium.
  • Types include Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), and Wavelength Division Multiplexing (WDM).
  • At the receiver end, the signals are separated using a demultiplexer.
  • It increases bandwidth utilization and reduces communication cost.

UNIT 4

  1. Encapsulation (2 marks) Encapsulation is the process of adding headers (and sometimes trailers) to data as it moves through different layers of a network.
  • Each layer adds its own control information to ensure proper transmission.
  1. Functions of OSI Layers (2 marks)
  • Presentation Layer: Performs data formatting, encryption, and compression.
  • Physical Layer: Handles transmission of raw bits over the medium.
  • Network Layer: Responsible for routing and IP addressing. 3) Layered Architecture of OSI Model (4 marks) The OSI (Open Systems Interconnection) model is divided into 7 layers , each with specific functions. It follows a layered architecture , where each layer communicates with its adjacent layers. Layers of OSI Model (Top to Bottom)
  1. Application Layer โ€“ Provides network services to end users
  2. Presentation Layer โ€“ Handles data formatting, encryption, compression
  3. Session Layer โ€“ Manages sessions and connections
  4. Transport Layer โ€“ Ensures reliable data transfer
  5. Network Layer โ€“ Handles routing and logical addressing
  6. Data Link Layer โ€“ Responsible for framing and error detection
  7. Physical Layer โ€“ Transmits raw bits over the medium
  1. Difference between OSI and TCP/IP Model (2 marks) OSI Model TCP/IP Model 7 layers 4 layers Reference model Practical model Developed by ISO Developed by DARPA Strict layer separation Flexible layer structure

2. First address (Network Address) For /24 โ†’ last 8 bits are host bits โ†’ set them to 0 IP: 129.65.33. 0 โœ” **First address: 129.65.33.

  1. Last address (Broadcast Address)** Set last 8 bits to 1 IP: 129.65.33. 255 โœ” Last address: 129.65.33. Final Answer (4 marks format):
    • Number of addresses: 256
    • First address: 129.65.33.
    • Last address: 129.65.33.
  1. Explain classes of IPv 4 with range Classes of IPv4 with Range (2 marks) - Class A: 1.0.0.0 โ€“ 127.255.255. - Class B: 128.0.0.0 โ€“ 191.255.255. - Class C: 192.0.0.0 โ€“ 223.255.255. - Class D: 224.0.0.0 โ€“ 239.255.255.255 (Multicast) - Class E: 240.0.0.0 โ€“ 255.255.255.255 (Experimental) UNIT 5
  2. **Network Topologies (2 marks each โ€“ definition + simple diagram)
  1. Bus Topology Definition:** All devices are connected to a single main cable (backbone). PC1 โ”€โ”€ PC2 โ”€โ”€ PC3 โ”€โ”€ PC 2. Ring Topology Definition: Devices are connected in a circular form , where each node is connected to two others.

PC1 โ”€โ”€ PC2 โ”€โ”€ PC3 โ”€โ”€ PC

__________________/

3. Star Topology Definition: All devices are connected to a central hub/switch. PC | PC1 โ€” HUB โ€” PC | PC 4. Mesh Topology (you wrote โ€œnestโ€) Definition: Each device is connected to every other device. PC1 โ€”โ€” PC | \ / | | / | | /\ | | / \ | PC3 โ€”โ€” PC 5. Tree Topology Definition: A hierarchical structure combining multiple star networks. Root / Hub1 Hub / \ / PC PC PC PC

  1. Router (4 marks) A router is a networking device that connects multiple networks and forwards data packets between them.
    • It operates at the Network Layer (Layer 3) of the OSI model.
    • It uses IP addresses to determine the best path for data transmission.
    • Routers use routing tables and protocols to direct traffic efficiently.
    • It connects LANs to WANs , such as connecting a home network to the internet.