OSI Reference model notes with interview questions

Earlier there was no reference model for devices.At that time a company can only use a specific vendors device only.There will not be intercompactability between different vendors product.To solve this issue,Open Systems Interconnection (OSI) model was developed by the International Organization for Standardization (ISO).

Layer
Description
Examples
7.
Application
Provides interface for users to communicate with applications.Responsible for initiating or services the request.
SMTP, DNS, HTTP, and Telnet etc
6.
Presentation
The Presentation layer controls theformatting  and syntax of user data for the application layer. This ensures that data from the sending application can be understood by the receiving application.
JPEG,MP3,MPEG etc
5.
Session
Responsible for establishing, managing, and terminating the session. If a session is broken, this layer can attempt to recover the session.
NetBIOS
4.
Transport
Breaks information into segments and is responsible for connection and connectionless communication.
TCP and UDP
3.
Network
Responsible for logical addressing and routing.Packets are formed in network layer
IP, ICMP,  and routers
2.
Data Link
Responsible for physical addressing, error correction, and preparing the information for the media.Frames present here.Consist of two sublayers LLC and MAC
MAC address, CSMA/CD, switches, and bridges
1.
Physical
Deals with the electrical signal.
Cables, connectors, hubs, and repeaters


OSI Model Interview Questions
  • List the layers of OSI ?
  • What are the responsibilities of Data Link Layer?
  • What are the responsibilities of Network Layer?
  • What are the responsibilities of Transport Layer?
  • Routers work at which OSI layers?
  • Switches work at which OSI layer ?
  • In which layer term "Frames" is used ?
  • In which layer term "Packets" is used ?
  • In which layer term "Segments" is used ?
  • Give some example for protocols work in Application layer ?
  • What is CRC? Which layer CRC works ?
  • What is the purpose of the Data Link?
  • What is a Window in networking terms?
  • What is the role of the LLC sublayer in datalink layer?
  • What is the function of the Application Layer in networking?
  • What are the difference between TCP and UDP?
  • What is the port no of DNS and Telnet?
  • Which service use both TCP and UDP ?
  • What is the port no of SMTP and POP3?
  • Which one is reliable – TCP or UDP ?

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6 comments:

  1. where is the answer of above Qs?

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    Replies
    1. Study OSI Model which is on top,from their you'll get all the answers

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