The 7-layer OSI (Open Systems Interconnection) model is a conceptual framework used to understand and implement computer network protocols. It divides the communication system into seven distinct layers, with each layer having specific responsibilities in handling data transmission between devices over a network. The OSI model was developed by the International Organization for Standardization (ISO) in 1984 and is used as a reference model for network communication.
40 MCQs with answer based on 7 Layer OSI Model
1. What does OSI stand for?
a) Open System Intercommunication
b) Open Software Interconnection
c) Open System Interconnection
d) Open Software Interface
Answer: c) Open System Interconnection
Explanation: OSI is the Open System Interconnection model, a conceptual framework for communication in networks.
2. How many layers are there in the OSI model?
a) 5
b) 6
c) 7
d) 8
Answer: c) 7
Explanation: The OSI model consists of 7 layers, each with distinct functions.
3. Which organization developed the OSI model?
a) IEEE
b) ISO
c) ITU
d) W3C
Answer: b) ISO
Explanation: The International Organization for Standardization (ISO) developed the OSI model in 1984.
4. Which layer of the OSI model is responsible for data encryption?
a) Application Layer
b) Presentation Layer
c) Session Layer
d) Transport Layer
Answer: b) Presentation Layer
Explanation: The Presentation Layer handles encryption, ensuring data security during transmission.
5. At which layer is the physical connection established?
a) Network Layer
b) Transport Layer
c) Physical Layer
d) Data-Link Layer
Answer: c) Physical Layer
Explanation: The Physical Layer deals with establishing, maintaining, and deactivating physical connections.
6. Which layer is closest to the end-user?
a) Application Layer
b) Presentation Layer
c) Session Layer
d) Transport Layer
Answer: a) Application Layer
Explanation: The Application Layer is the closest to the end-user and interacts directly with software applications.
7. What is the main function of the Data-Link Layer?
a) Frame routing
b) Error-free transfer of data frames
c) Data encryption
d) Physical data transmission
Answer: b) Error-free transfer of data frames
Explanation: The Data-Link Layer ensures that data is transferred without errors across the physical network.
8. Which of the following is NOT a function of the Physical Layer?
a) Line configuration
b) Signal transmission
c) Error control
d) Topology definition
Answer: c) Error control
Explanation: Error control is handled by the Data-Link Layer, not the Physical Layer.
9. What is the name of the sub-layer that manages data access control at the Data-Link Layer?
a) Logical Link Control
b) Media Access Control
c) Network Control
d) Physical Control
Answer: b) Media Access Control
Explanation: The Media Access Control (MAC) sub-layer handles access to the physical transmission medium.
10. Which layer is responsible for routing data packets?
a) Data-Link Layer
b) Transport Layer
c) Network Layer
d) Session Layer
Answer: c) Network Layer
Explanation: The Network Layer is responsible for routing packets and determining the best path for data transmission.
11. Which layer breaks down large messages into smaller segments?
a) Application Layer
b) Presentation Layer
c) Transport Layer
d) Session Layer
Answer: c) Transport Layer
Explanation: The Transport Layer divides data into smaller segments to ensure proper transmission.
12. Which layer handles synchronization and dialog control?
a) Session Layer
b) Presentation Layer
c) Network Layer
d) Application Layer
Answer: a) Session Layer
Explanation: The Session Layer establishes and maintains connections and handles synchronization.
13. What is the responsibility of the Presentation Layer in the OSI model?
a) Routing
b) Translation and encryption
c) Error correction
d) Addressing
Answer: b) Translation and encryption
Explanation: The Presentation Layer is responsible for data translation and encryption.
14. Which layer adds headers to the data to create segments?
a) Network Layer
b) Data-Link Layer
c) Transport Layer
d) Session Layer
Answer: c) Transport Layer
Explanation: The Transport Layer adds headers containing sequence numbers to data segments.
15. Which protocol works at the Transport Layer?
a) TCP
b) HTTP
c) IP
d) FTP
Answer: a) TCP
Explanation: Transmission Control Protocol (TCP) operates at the Transport Layer to ensure reliable data transmission.
16. Which layer deals with physical hardware connections and transmission mediums?
a) Data-Link Layer
b) Network Layer
c) Physical Layer
d) Transport Layer
Answer: c) Physical Layer
Explanation: The Physical Layer handles the actual hardware connections and transmission mediums.
17. Which function is performed by the Network Layer?
a) Dialog control
b) Data framing
c) Routing
d) Flow control
Answer: c) Routing
Explanation: Routing is a primary function of the Network Layer.
18. Which of the following is a layer in the OSI model?
a) Transmission Layer
b) Encryption Layer
c) Presentation Layer
d) Data Layer
Answer: c) Presentation Layer
Explanation: The Presentation Layer deals with data translation and encryption.
19. Which OSI layer is concerned with file transfer and management?
a) Presentation Layer
b) Application Layer
c) Transport Layer
d) Data-Link Layer
Answer: b) Application Layer
Explanation: The Application Layer provides services such as file transfer and management.
20. Which layer is responsible for flow control in data transmission?
a) Application Layer
b) Data-Link Layer
c) Transport Layer
d) Network Layer
Answer: b) Data-Link Layer
Explanation: The Data-Link Layer ensures proper flow control in data transmission.
21. Which layer is also called the ‘end-to-end’ layer?
a) Application Layer
b) Network Layer
c) Transport Layer
d) Data-Link Layer
Answer: c) Transport Layer
Explanation: The Transport Layer is called the ‘end-to-end’ layer because it provides communication from source to destination.
22. What does the Data-Link Layer do with raw bits received from the Physical Layer?
a) It converts them into signals
b) It discards them
c) It organizes them into frames
d) It encrypts them
Answer: c) It organizes them into frames
Explanation: The Data-Link Layer frames raw bits received from the Physical Layer for further processing.
23. Which of the following functions is performed by the Session Layer?
a) Framing
b) Dialog control
c) Packetizing
d) Error control
Answer: b) Dialog control
Explanation: The Session Layer manages dialog control and synchronization between communicating systems.
24. Which layer ensures that data segments are reassembled correctly at the destination?
a) Transport Layer
b) Network Layer
c) Presentation Layer
d) Session Layer
Answer: a) Transport Layer
Explanation: The Transport Layer ensures data segments are reassembled in the correct order at the destination.
25. Which protocol is unreliable and operates at the Transport Layer?
a) TCP
b) HTTP
c) UDP
d) FTP
Answer: c) UDP
Explanation: User Datagram Protocol (UDP) is an unreliable, connectionless protocol at the Transport Layer.
- Which layer is responsible for encryption and decryption of data?
- a) Network Layer
- b) Data Link Layer
- c) Presentation Layer
- d) Transport Layer
Answer: c) Presentation Layer
Explanation: The Presentation Layer is responsible for encryption and decryption, as it deals with data security and format conversion. - The process of converting data from sender-dependent format to a common format occurs in which layer?
- a) Application Layer
- b) Transport Layer
- c) Network Layer
- d) Presentation Layer
Answer: d) Presentation Layer
Explanation: The Presentation Layer is responsible for data translation between different systems.
- Which of the following protocols operates at the Transport Layer?
- a) IP
- b) TCP
- c) HTTP
- d) FTP
Answer: b) TCP
Explanation: Transmission Control Protocol (TCP) operates at the Transport Layer and ensures reliable data transfer.
- Which layer of the OSI model ensures end-to-end communication and error-free delivery?
- a) Data Link Layer
- b) Transport Layer
- c) Network Layer
- d) Physical Layer
Answer: b) Transport Layer
Explanation: The Transport Layer ensures error-free delivery and manages the flow of data between the source and destination.
- What is the purpose of the Session Layer in the OSI model?
- a) Routing and switching
- b) Data encryption
- c) Establishing, managing, and terminating sessions
- d) Error correction
Answer: c) Establishing, managing, and terminating sessions
Explanation: The Session Layer manages the establishment, maintenance, and termination of sessions between applications.
- Which of the following best describes flow control at the Data Link Layer?
- a) Adjusts the speed of transmission between devices
- b) Encrypts and compresses data
- c) Routes packets over the best path
- d) Manages error detection and correction
Answer: a) Adjusts the speed of transmission between devices
Explanation: Flow control ensures that data transmission speed is balanced between devices to prevent data overflow.
- The header added by the Network Layer includes which of the following?
- a) Physical address
- b) Source and destination IP addresses
- c) Service-point address
- d) Data encryption
Answer: b) Source and destination IP addresses
Explanation: The Network Layer adds the source and destination IP addresses for routing data.
- Which of the following services is provided by the Application Layer?
- a) Routing
- b) File transfer, access, and management (FTAM)
- c) Encryption
- d) Flow control
Answer: b) File transfer, access, and management (FTAM)
Explanation: The Application Layer provides services like file transfer, email, and directory services.
- Which OSI layer is responsible for the physical addressing of frames?
- a) Transport Layer
- b) Network Layer
- c) Data Link Layer
- d) Presentation Layer
Answer: c) Data Link Layer
Explanation: The Data Link Layer is responsible for adding the physical addresses to frames for correct delivery.
- Which layer breaks data into smaller segments for transmission?
- a) Physical Layer
- b) Transport Layer
- c) Data Link Layer
- d) Network Layer
Answer: b) Transport Layer
Explanation: The Transport Layer breaks the data into segments to ensure efficient transmission.
- Which of the following devices operates at the Physical Layer of the OSI model?
- a) Router
- b) Switch
- c) Hub
- d) Firewall
Answer: c) Hub
Explanation: A Hub operates at the Physical Layer and simply transmits data without inspecting it.
- Which OSI layer is primarily concerned with how the data is presented to the user?
- a) Session Layer
- b) Application Layer
- c) Presentation Layer
- d) Transport Layer
Answer: c) Presentation Layer
Explanation: The Presentation Layer is responsible for how data is presented, including format and encoding.
- In the OSI model, which layer is responsible for error detection and retransmission?
- a) Application Layer
- b) Transport Layer
- c) Data Link Layer
- d) Network Layer
Answer: c) Data Link Layer
Explanation: The Data Link Layer handles error detection and retransmission through mechanisms like CRC.
- Which protocol is considered unreliable at the Transport Layer?
- a) TCP
- b) UDP
- c) IP
- d) HTTP
Answer: b) UDP
Explanation: User Datagram Protocol (UDP) is unreliable because it does not guarantee packet delivery or acknowledgment.
- What is the main responsibility of the Physical Layer?
- a) Error-free transmission of data
- b) Transmitting individual bits over a physical medium
- c) Ensuring data integrity and error control
- d) Managing the IP addressing of devices
Answer: b) Transmitting individual bits over a physical medium
Explanation: The Physical Layer transmits raw bits over the physical communication channel, defining the electrical and mechanical specifications.
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