OSI Model Most Frequently asked Interview Questions & Answers

What is OSI Model?

OSI means Open System Interconnection. You can find 7 layers in the OSI model and each layer includes a different capability. OSI model helps networking professionals in understanding information flow from source to destination. Even though the OSI model not performing any function in the networking process. All devices and software applications use the OSI model to explain data flow between source and destination.

Can you list the layers of the OSI reference model?

There are 7 OSI layers: 


  1. In your view is there any alternative model to the OSI model? 

TCP/IP could be the alternate model that also explains the data flow in the network. It is a less complicated representation compared to the OSI model but contains fewer details of protocols compared to the OSI model.

  1. How TCP protocol differs from UDP protocol?
Transmission Control ProtocolUser Datagram Protocol
Connection-Oriented ProtocolConnection Less Protocol
Reads data as streams of bytes and therefore the message is transmitted to segment boundaries.UDP messages consist of packets that are sent one by one. It also checks the integrity at arrival.
High reliabilityMore transmission timeLow reliabilityLess transmission time
TCP rearranges data packets in a specific order.UDP protocol doesn’t have a fixed order because all packets are independent of each other.
Three-way handshakeNo handshake
The speed for TCP is slower.UDP is faster as the recovery of error is not attempted.
Header size is 20 bytesThe header size is 8 bytes.
Acknowledgment segmentsNo Acknowledgment segments
TCP does error checking and also error recovery.UDP performs error checking, but it discards incorrect/invalid packets.
TCP is reliable because it guarantees the delivery of knowledge to the destination router.The delivery of deets to the destination cannot be guaranteed in UDP.
TCP provides extensive error checking mechanisms because it provides flow control and acknowledgment of data.UDP has just one error checking mechanism that’s used for checksums.
  1. Which layers perform error detection and flow control?

On receiving and while transmission of information, Layer 2 – Data Link layer decode and encode data into bits. The data link layer can be further divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. This layer also does the task of error checking and flow control.

  1. What is the difference between half-duplex and full-duplex?

In half-duplex, information can flow in both directions although not simultaneously. During full-duplex, information can flow in both directions simultaneously.

  1. What are the different protocols of each layer in the OSI Model?
Layer 1PhysicalRS232, 100BaseTX, ISDN, 11.
Layer 2Data LinkRAPA, PPP, Frame Relay, ATM, Fiber Cable, etc.
Layer 3NetworkIPV5, IPV6, ICMP, IPSEC, ARP, MPLS.
Layer 4TransportTCP, UDP
Layer 5SessionNetBIOS, SAP
Layer 6PresentationMPEG, ASCH, SSL, TLS
Layer 7ApplicationSMTP, HTTP, FTP, POP3, SNMP
  1. What is do you understand by TCP/IP Model?

Transmission Control Protocol / Internet Protocol is the full form for TCP/IP. This is a couple of protocol layers that was created to make data exchange possible on various kinds of computer networks, also referred to as a heterogeneous network.

  1. What is HTTPS and which port does it use?

HTTPS is just a Secure HTTP. HTTPS is employed for secure communication over some type of computer network. HTTPS provides authentication to the websites that prevent unwanted attacks. In bi-directional communication, the HTTPS protocol encrypts the communication so the tampering of the info gets avoided. With assistance from an SSL certificate, it verifies if the requested server connection is just a valid connection or not. HTTPS uses TCP with port 443.

  1. What is Network Layer all about under the OSI reference model?

The Network layer is mainly responsible for data routing, packet switching, and network congestion control. The routers operate under this layer.

  1. Explain the main importance of the Physical Layer in the OSI Model.

The physical layer’s conversions are done from the data bits to the electrical signal, and vice versa. This is where network devices and cable types are thought and set up.

  1. Explain the functions of the OSI Session Layer.

This layer offers the protocols and means for just two devices on the network to communicate with each other by holding a session. This includes creating the session, managing information exchange during the session, and the tear-down process upon termination of the session.

  1. What role does OSI play in computer networks?

OSI (Open Systems Interconnect) serves as a guide model for data communication. It is made up of 7 layers, with each layer defining a particular facet of how network devices connect and speak with one another. One layer may handle the physical media used, while another layer dictates how data is transmitted throughout the network.

  1. What protocols come under the Application layer of the TCP/IP?

These are the protocols under the TCP/IP Application layer: 

  • FTP
  • TFTP
  • Telnet
  • SMTP
  1. What is SMTP?

SMTP is short for Simple Mail Transfer Protocol. This protocol deals with all internal mail and provides the required mail delivery services on the TCP/IP protocol stack.

  1. What protocols fall under the TCP/IP Internet Layer?

There are 4 protocols that are being managed by this layer. 

  • ICMP
  • IGMP
  • IP
  • ARP
  1. What are the differences between MAC addresses and IP addresses?
MAC AddressIP Address
MAC address is Media Access Control Address.IP address stands for Internet Protocol Address.
It consists of a 48-bit address.It consists of a 32-bit address.
MAC address comes under the link layer of the OSI model.IP address comes under the network layer of the OSI model.
It is referred to as a physical address.It is referred to as a logical address.
You can redeem the MAC address of any device using the ARP protocol.You can redeem the IP address of any device RARP protocol.
Classes are not used in MAC addresses.IP addresses consist of IPv4 that use A, B, C, D, and E classes.
  1. Can you explain why the layers of the OSI model important to the network administrator?

The Layers of OSI Model are important for the network administrator in this manner-

i. To troubleshoot network problems by verifying the functionality of each layer.

ii. In many cases it requires the network administrator to isolate at which layer the network problem occurs.

  1. What happens in the presentation layer?

Encryption. The presentation layer encrypts data to be sent throughout the network and decrypts it so that it could be accessed by the application form layer on the receiving end.

  1. What are Unicast, Multicast, and Broadcast?

Unicast communication is from a device on the network to another device on the network.

Multicast communication is from a device on the network to many, but not absolutely all, devices on the network.

Broadcast communication is from devices on the network to all devices on the network.

Leave a Comment

Your email address will not be published. Required fields are marked *