OSI stands for Open System Interconnection Basic Reference model. It is an abstract description for layered communications and computer network protocol design It divides the network in seven layers, from top to bottom, as follows:
1. Application: Network process to application (Data layer)
2. Presentation: Data representation and encryption (Data layer)
3. Session: Interhost communication (Data layer)
4. Transport: End-to-End connection and reliability (Segments layer)
5. Network: Path determination and IP (Logical addressing) (Packets layer)
6. Data-Link: MAC and LLC (Physical addressing) (Frames layer)
7. Physical: Media, signal and binary transmission (Bits layer)

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Solved Example: 9990-01

The number of layers in ISO OSI reference model is: (UPRVUNL JE ME Oct 2021- Shift I)

A. 2

B. 7

C. 6

D. 4

The seven layers in OSI model are:

• Physical layer
• Data link
• Network
• Transport
• Session
• Presentation
• Application

Correct Answer: B

Solved Example: 9990-02

Transport layer: (UPPCL AE CS Nov 2016)

A. Provide end to end error detection and correction

B. Handles connection to the network by higher layer

C. Is the highest layer among all the OSI layers

D. Define physical characteristics of the network

Correct Answer: A

Solved Example: 9990-03

Consider the following statements regarding the OSI model: (ESE Electronics Prelims 2021)
Statement 1: Application layer provides the control structure for communication between applications
Statement 2: Data link layer provides for the reliable transfer of information across the physical link.
Statement 3: Transport layer provides end-to-end error recovery and flow control of data.

A. 1 and 2 only

B. 1 and 3 only

C. 1,2 and 3

D. 2 and 3 only

Statement 1 is FALSE because the session layer provides the control structure specified.

Statement 2 is TRUE

Statement 3 is TRUE

Correct Answer: D

Solved Example: 9990-04

In OSI model accounting, addressing and routing functions of the system are provided by: (UPPCL JE Electrical Nov 2019- Shift II)

A. Application layer

B. Network layer

C. Transport layer

D. Physical layer

Correct Answer: B

Solved Example: 9990-05

The data-link layer is responsible for: (EKT CS Paper II: Set 02/2015)

A. Incoming bit stream and simply repeats to other devices connected

B. An error free communication across the physical link connecting primary and secondary stations within a network

C. An end-to-end integrity of data message propagated through the network between two devices

D. Logical connection at application layer

Correct Answer: B

Solved Example: 9990-06

The device bridge is used at ____ layer of OSI reference model. (KVS PGT Computer Science 2018)

A. Datalink

B. Network

C. Transport

D. Application

Correct Answer: A

Solved Example: 9990-07

Which layer in the OSI model provides the data transfer in the form of frames across the transmission link? (MP Vyapam Sub-Engineer Electrical Jul 2017)

A. Data link layer

B. Physical layer

C. Network layer

D. Session layer

Correct Answer: A

• The Internet Protocol Suite (commonly known as TCP/IP) is the set of communications protocols used for the internet and other similar networks.
• It is named from two of the most important protocols in it:
  • The Transmission Control Protocol (TCP)
  • The Internet protocol (IP)
• The layers are:
  1. Application services: It provides a way for applications to have access to networked services
  2. Transport: This layer acts as the delivery service used by the application layer. It also handles all error detection and recovery.
  3. Internet: Organizes or handles the movement of data on network.
  4. Network interface: This layer consists of device drivers in the OS and the network interfae card attached to the system. Both the device drivers and the network interface card take care of the communication details with the media being used to transfer the data over the network.

Solved Example: 9991-01

How many layers are present in the Internet protocol stack? (How many layers are present in the Internet protocol stack? (UPPCL Asst Accountant Sept 2021)

A. 6

B. 3

C. 5

D. 7

The TCP/IP model has five layers:

• Physical layer
• Data Link layer
• Network layer
• Transport layer
• Application layer

Correct Answer: C

Solved Example: 9991-02

The TCP/IP model does not have ____ and _____ layers but ___ layer include required functions of these layers. (HTET PGT Computer Science 2017)

A. Session, Application, Presentation

B. Presentation, Application, Session

C. Session, Presentation, Application

D. Link, Internet, Transport

Correct Answer: C

Solved Example: 9991-03

Which of the following is a network layer protocol? (UPPCL Asst Accountant Jan 2019)

A. IP

B. SMTP

C. HTTP

D. TCP

Correct Answer: A