H. Vignesh RamamoorthyM.Sc (Softw Engg), MCA, AssistantProfessorUG – Computer Science                                    1
OSI Reference Model    • OSI: Open System Interconnection .    • Developed by the International      Organization for Stan...
OSI Model Layers       Layer - 7   Application                   Application                                   Upper Layer...
Application Layer                    Application Layer is Application Application Application  Application       responsib...
Examples of Networking Services Service         Port No. HTTP              80 FTP               21 SMTP              25 TE...
Data flow from Application Layer                    Application                    Application         Data               ...
Presentation Layer                 Presentation Layer is Application Application     responsible for converting data      ...
Data flow from Presentation Layer                    Application                    Application     Data                  ...
Session Layer Application Application                Session Layer is responsible for Presentation Presentation   establis...
Data flow from Session Layer                   Application                   Application    Data                   Present...
Transport Layer                  Transport Layer is Application      responsible for end-to-end Application               ...
Identifying Service                 TCP                      UDP    • Transmission Control   • User Datagram      Protocol...
Multiplexing & De-multiplexing                    Application                    Application                   Presentatio...
Data flow from Transport Layer                   Application                   Application      Data                   Pre...
Network Layer                Network Layer is Application Application    responsible for providing best                pat...
Data flow from Network Layer                   Application                   Application     Data                  Present...
Datalink Layer                 Datalink Layer is Application Application     divided into two Sub Layers : Presentation Pr...
Data flow from Data Link Layer                    Application                    Application      Data                   P...
Physical Layer                 Physical Layer is Application Application     responsible for electrical,                 m...
Data flow from Physical Layer                    Application                    Application    Data                   Pres...
Data Encapsulation & De-capsulation     A                                            B Application       Data            D...
Comparing OSI with TCP/IP Layers         OSI Layers           TCP/IP Layers         Application         Application       ...
Thank Youhvigneshram@yahoo.com                        23
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Cn osi model

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Cn osi model

  1. 1. H. Vignesh RamamoorthyM.Sc (Softw Engg), MCA, AssistantProfessorUG – Computer Science 1
  2. 2. OSI Reference Model • OSI: Open System Interconnection . • Developed by the International Organization for Standardization in 1974. • There are seven layers in OSI reference Model . • process or role 2
  3. 3. OSI Model Layers Layer - 7 Application Application Upper Layer Layer - 6 Presentation Presentation or Software Layer Layer - 5 Session Session Layer - 4 Transport Transport Heart of OSI Layer - 3 Network Network Lower Layer Layer - 2 Data Link Data Link or Hardware Layer Layer - 1 Physical Physical 3
  4. 4. Application Layer Application Layer is Application Application Application Application responsible for providing Networking Services to the Presentation Presentation user. It is also known as Desktop Layer. Identification of Session Session Services is done using Port Numbers. Transport Transport Ports are Entry and Exit Points Network Network to the Layer Data Link Data Link Total No. Ports 0 – 65535 Physical Reserved Ports 0 – 1023 Physical Open Client Ports 1024 – 65535 4
  5. 5. Examples of Networking Services Service Port No. HTTP 80 FTP 21 SMTP 25 TELNET 23 TFTP 69 5
  6. 6. Data flow from Application Layer Application Application Data 80 21 25 53 67 69 Presentation Presentation Session Session Transport Transport Network Network Data Link Data Link Physical Physical 6
  7. 7. Presentation Layer Presentation Layer is Application Application responsible for converting data into standard format. Presentation Presentation Presentation Presentation Examples : ASCII, EBCDIC, Session Session JPEG, MPEG, BMP, MIDI, WAV, MP3 Transport Transport Network Following tasks are perform at Network Presentation layer : Data Link Data Link Encoding – Decoding Physical Physical Encryption – Decryption Compression – Decompression 7
  8. 8. Data flow from Presentation Layer Application Application Data Presentation Presentation Data Session Session Transport Transport Network Network Data Link Data Link Physical Physical 8
  9. 9. Session Layer Application Application Session Layer is responsible for Presentation Presentation establishing, maintaining and terminating session. Session Session Session Session ID works at Session Layer. Transport Transport Network Network Examples : Data Link Data Link RPC  Remote Procedure Call Physical SQL  Structured Query Language Physical NFS  Network File System 9
  10. 10. Data flow from Session Layer Application Application Data Presentation Presentation Data Session Session Data Transport Transport Network Network Data Link Data Link Physical Physical 10
  11. 11. Transport Layer Transport Layer is Application responsible for end-to-end Application connectivity. It is also known as Presentation the heart of OSI Layers. Presentation Following tasks are performed at Session the Transport Layer : - Session Transport Transport Transport Transport • Identifying Service • Multiplexing & De-multiplexing Network Network • Segmentation Data Link Data Link • Sequencing & Reassembling • Error Correction Physical Physical • Flow Control 11
  12. 12. Identifying Service TCP UDP • Transmission Control • User Datagram Protocol Protocol • Connection Oriented • Connection Less • Acknowledgement • No Acknowledgement • Reliable • Unreliable • Slower • Faster • Port No. 6 • Port No. 17 • e.g. HTTP, FTP, SMTP • e.g. DNS, DHCP, TFTP 12
  13. 13. Multiplexing & De-multiplexing Application Application Presentation Presentation Session Session 80 21 25 53 67 69 Transport Transport TCP - 6 UDP - 17 Network Network Data Link Data Link Physical Physical 13
  14. 14. Data flow from Transport Layer Application Application Data Presentation Presentation Data Session Session Data Transport TH Segment Data Transport Network Network Data Link Data Link Physical Physical 14
  15. 15. Network Layer Network Layer is Application Application responsible for providing best path for data to reach the Presentation Presentation destination. Logical Addressing works on this layer. Router is a Session Session Network Layer device. Transport Transport It is divided into two parts Network Network • Routed Protocols Network Network e.g. IP, IPX, Apple Talk. Data Link Data Link • Routing Protocols Physical e.g. RIP, IGRP, OSPF, EIGRP Physical 15
  16. 16. Data flow from Network Layer Application Application Data Presentation Presentation Data Session Session Data e.g. Router Transport Transport Segment Network Network Packet NH Segment Data Link Data Link Physical Physical 16
  17. 17. Datalink Layer Datalink Layer is Application Application divided into two Sub Layers : Presentation Presentation • LLC – Logical Link Control Session It talks about Wan protocols e.g. Session PPP, HDLC, Frame-relay Transport Transport • MAC – Media Access Control Network Network It talks about Physical Address. It is a 48 bit address i.e. 12 digit Data Link Data Link Data Link Data Link Hexadecimal Number. It is also responsible for Error Physical Physical Detection Devices working on Data Link Layer are Switch, Bridge, NIC. 17
  18. 18. Data flow from Data Link Layer Application Application Data Presentation Presentation Data Session Session Data Transport Transport Segmente.g. Switch Network Network Packet Data Link Data Link DH Frame DT Packet Physical Physical 18
  19. 19. Physical Layer Physical Layer is Application Application responsible for electrical, mechanical and procedural checks. Presentation Presentation Data will be converted into Binary (i.e.) 0’s & 1’s. Data will be in the Session Session form of electrical pulses if it is Coaxial or Twisted Pair cable and in Transport Transport the form of Light if it is Fiber Optic Cable. Network Network Devices working at Physical Layer Data Link Data Link are Hubs, Repeaters, Cables, Modems etc. Physical Physical Physical Physical 19
  20. 20. Data flow from Physical Layer Application Application Data Presentation Presentation Data Session Session Data Transport Transport Segment Network Network Packete.g. Hub Data Link Data Link Frame Physical Physical Bits 20
  21. 21. Data Encapsulation & De-capsulation A B Application Data Data Application Application Application Presentation Presentation Data Data Presentation Presentation Session Session Data Data Session Session Transport TH TransportTH Transport Data Segment TH Segment Data Transport Network Network NH Segment Packet NH Segment Packet Network Network NH Data Link Data Link DHFrameDT Packet DTFrameDH Packet Packet DH Data LinkDT Data Link Physical Physical Bits Bits Physical Physical 21
  22. 22. Comparing OSI with TCP/IP Layers OSI Layers TCP/IP Layers Application Application Presentation Presentation Application Application Session Session Transport Transport Transport Transport Network Network Internet Internet Data Link Data Link Network Network Access Access Physical Physical 22
  23. 23. Thank Youhvigneshram@yahoo.com 23

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