Interview Questions on- OSI model
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Interview Questions on- OSI model

OSI is popularly known as open system interconnection. Here we bring Interview questions on OSI Model which commonly asked in most interviews. If In your mind you think that question should also be included in this OSI Model interview question. Put that question in the comment section we will verify and include so, Every Jobseeker will be benefited from these questions.

OSI Model Interview Questions And Answers

Que: List the layers of OSI?

Ans: From top to bottom, OSI layers are, Application, Presentation, Session, Transport, Network, Data Link, and Physical Layer.

Que: Are there any alternate models to the OSI model?

Ans: TCP/IP is the alternate model which defines the flow of data in the network



Que: What are the responsibilities of the Data Link Layer?

Ans: Framing, Error detection, CRC and Physical Addressing is the task of Data Link Layer.

Que: What are the responsibilities of the Network Layer?

Ans: Routing, IP Addressing, and Path determination are the main responsibilities of the Network Layer.

Que: What are the responsibilities of the Transport Layer?

Ans: Transport Layer has a lot of functions. These are

  1. Multiplexing and De-Multiplexing
  2. Segmentation and Re-assembly
  3. Flow Control
  4. Error Correction
  5. Connection Establishment
  6. Sequencing
  7. 3-way Handshake

Que: What is the difference between TCP and UDP?

User Datagram Protocol
Transmission Control Protocol
Header Size - 8 Bytes
Header Size - 20 Bytes
Live broadcasts, DNS, VoIP, TFTP
World Wide Web (HTTP, HTTPS) ,SSH,FTP,Email (SMTP, IMAP/POP)

Que: Routers work at which OSI layer?

Ans: Network Layer

Que: Switches work at which OSI layer?

Ans: Layer 2 and Some Switches can operate at Layer 3

Que: Which Layer perform error detection and flow control?

Ans: Layer 2 in OSI Model -Data Link Layer decoded and encoded into bits.The data link layer is mainly divided into two sublayers. The Media Access Control (MAC)Layer and the Logical Link Control(LLC) layer.This layer  also perform error checking and flow control.

Que: What is Data Encapsulation?

Ans: Data encapsulation is the process where extra control information is added to the data before being passed to the layer below.

A Protocol data unit (PDU) is an OSI term given to the chunks of information either added (encapsulation) or removed (decapsulation) by an OSI layer.

Que: What is a Window in networking terms?

Ans: Window is the amount of segments sent by TCP between two acknowledgements.

Que: What is the function of the Application Layer in networking?

Ans: Application Layer is responsible for providing a user interface in between user and Network with the help of applications like web browsers.

Que: What are the differences between MAC Sublayer and LLC sublayer in DataLink Layer?

Ans: MAC sublayer stands for Media Access Control layer.MAC address work on Layer 2 of OSI Model -Data link Layer.This Layer  controls the permission of data to transmit it.

LLC sublayer stands for Logical Link control layer.This Layer controls frame synchronization,Flow control,error checking.

Que: Which service use both TCP and UDP ?

Ans: DNS uses both TCP and UDP

Que: In which layer term “Frames” is used ?

Ans: Frames are PDU of Data Link Layer

Que: In which layer term “Packets” is used ?

Ans: Packets are PDU of Network Layer

Que: In which layer term “Segments” is used ?

Ans: Segments are used at Transport Layer

Que: Give some example for protocols work at Application layer ?

Ans: Application Layer Protocols are HTTP, HTTPs, Telnet, SSH, DNS, FTP, TFTP, DHCP, RIP

Que: What is CRC? Which layer CRC works ?

Ans: Cyclic Redundancy Check is used to detect the errors in network. It works at Data Link Layer (LLC Sub Layer).

Que: What is the purpose of the Data Link?

Ans: Data Link Layer is responsible for Framing, Error Detection and Physical Addressing

Que: Which one is reliable – TCP or UDP ?

Ans: TCP is reliable.

Que: What is the port number of ftp(data) and ftp control?

Ans: FTP port number 20 (Data); 21 for Control

Que: Which layer provides logical addressing that routers will use for path determination ?

Ans: Network Layer

Que: Which layer specifies voltage, wire speed, and pin out cables and moves bits between devices ?

Ans: Physical

Que: Which layer combines bits into bytes and bytes into frames, uses MAC addressing, and provide error detection ?

Ans: Data Link Layer

Que: Which layer is responsible for keeping the data from different applications separate on the network ?

Ans: Session layer.

Que: Which layer segments and resembles data into a data stream ?

Ans: Transport layer.

Que: Which layer provides the physical transmission of the data and handles error notification, network topology, and flow control ?

Ans: Data Link Layer

Que: Which Layer manages device addressing, tracks the location of devices on the network, and determine the best way to move data ?

Ans: Network layer.

Que: How Data breaks down on each layer from top to bottom ?

Ans: Data remain data in first three layer from top, it break into segment in Transport Layer.Packet in network Layer,In Data-link layer it break into frame and converted into bits in physical layer where transmission occur.

Que: Which layer is responsible for converting data packets from the Data Link layer into electrical signals ?

Ans: Physical Layer

Que: At which layer is routing implemented, enabling connections and path selection between two end systems?

Ans: Network Layer

Que: Which layer defines how data is formatted, presented, encoded,and converted for use on the network ?

Ans: Presentation Layer

Que: Which layer is responsible for creating, managing and terminating sessions between applications ?

Ans: Session Layer

Que: DNS uses which protocol? Why?

Ans: DNS uses both TCP and UDP

Que: Which layer is closer to the user?

Ans: From sender point of view, Application Layer is closest and from Receiver point of view Physical Layer is closest.

Que: Differentiate between forward lookup and reverse lookup in DNS?

Ans: Forward Lookup: Name to IP resolution

Reverse Lookup: IP to Name resolution;

Que: What is IPSec?

Ans: IPSec provides data security at the IP Packet Level.

Que: What is the way to establish a TCP connection?

Ans: TCP Connection is established using three-way Handshake.

Que: What is the difference between flow control and error control?

Ans: Error Controls the process of detecting and correcting both the bit and packet level error. While flow control is a mechanism to ensure the efficient delivery of Data. Flow control is agreeing on the minimum amount of data that a receiver can handle at a time.

Que: What is difference between Data Encapsulation and data de-encapsulation?

Ans: When data is transfer from the higher layer to the lower layer. Each layer adds its header to the original packet. This is known as Data Encapsulation.

When data is transferred from the lower layer to the higher layer, each layer removes the information added by the other layers. It will remove the headers added by other layers .This is known as Data de-encapsulation.


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