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OSI Model



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OSI model and different layers of OSI model

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OSI Model

  2. 2. OSI MODEL • OSI model is a reference tool for understanding data communication between any two networked system. • It divides the communication processes into 7 layers. • Each layer performs specific functions to support the layers above it and uses services of the layers below it. • Each layer represents a different level of abstraction and layers boundaries are well defined.
  3. 3. PHYSICAL LAYER • It coordinates the functions required to transmit a bit stream over a physical medium. • It deals with the mechanical and electrical specifications of interface and transmission medium. • It defines the procedures and functions that physical devices and interfaces have to perform for transmission to occur.
  4. 4. FUNCTIONS OF PHYSICAL LAYER • It defines characteristics of the interface between the devices and the transmission medium. • It defines the type of transmission medium and transmission rate. • It performs synchronization of sender and receiver clocks. • It is concerned with physical topology. • It transmits bit stream over the communication channel
  5. 5. UNITS USED IN PHYSICAL LAYER • Hardware used: Repeater and Hub • Data unit: Bit stream
  6. 6. DATA LINK LAYER • It transforms the physical layer, a raw transmission facility, to a reliable link and is responsible for Node-to-Node delivery. • It makes the physical layer appear error free to the upper layer (i.e., network layer).
  7. 7. FUNCTIONS OF DATA LINK LAYER • Framing • Flow control • Error control • Access control • Physical addressing
  8. 8. UNITS USED IN DATA LINK LAYER • Hardware used: Bridges and Switches • Data unit: Frames • Protocol used: Simplex protocol, stop and wait protocol, sliding window, HDLC, SDLC, NDP, ISDN, ARP, PSL, OSPF, NDP
  9. 9. NETWORK LAYER • It is responsible for source to destination delivery of a packet possibly across multiple networks (links). • If the two systems are connected to the same link, there is usually no need for a network layer. • If the two systems are attached to different links with connecting devices between networks, there is often a need of the network layer to accomplish source to destination delivery.
  10. 10. FUNCTIONS OF NETWORK LAYER • Logical addressing • Routing
  11. 11. UNITS USED IN NETWORK LAYER • Hardware used: Routers • Data units: Packets • Protocols used: IP(Internet Protocol), NAT(Network Address Translation), ARP(Address Resolution Protocol), ICMP(Internet Control Message Protocol), BGP(Border Gateway Protocol), RARP(Reverse Address Resolution Protocol), DHCP(Dynamic Host Configuration Protocol), BOOTP, OSPF
  12. 12. TRANSPORT LAYER • It is responsible for source to destination delivery of the entire message. • It ensures that the whole message arrives intact and in order.
  13. 13. FUNCTIONS OF TRANSPORT LAYER • Service point addressing • Segmentation and reassembly • Flow control • Error control • Connection control
  14. 14. UNITS USED IN TRANSPORT LAYER • Hardware used: Transport gateway • Data units: Segments • Protocol used: TCP(Transmission Control Protocol) for connection oriented approach and UDP(User Datagram Protocol) for connectionless approach
  15. 15. SESSION LAYER • It is the network dialog controller. • It establishes, maintains and synchronizes the interaction between communicating systems. • It plays an important role in keeping applications data separate.
  16. 16. FUNCTIONS OF SESSION LAYER • Dialog control • Synchronization
  17. 17. UNITS USED IN SESSION LAYER • Data unit: Data • Protocol used: ADSP, ASP, ISO-SP, L2TP, F2F, PAP, PPTP, RPC, SMPP, SDP, ZIP, RTCP
  18. 18. PRESENTATION LAYER • It is responsible for how an application formats data to be sent out onto the network. • It basically allows an application to read (to understand) the message.
  19. 19. FUNCTIONS OF PRESENTATION LAYER • Translation • Encryption and decryption • Compression
  20. 20. UNITS USED IN PRESENTATION LAYER • Data unit: Data • Protocol used: AFP, ASCII, EBCDIC, ICA, LPP, NCP, NDR, XDR, X.25 PAP
  21. 21. APPLICATION LAYER • It enables the user, whether human or software, to access the network. • It provides user interfaces and support for services such as electronic mail, remote file access and transfer shared database management and other types of distributed information services.
  22. 22. FUNCTIONS OF APPLICATION LAYER • Network virtual terminal • File transfer, access and management • Mail services • Directory services
  23. 23. UNITS USED IN APPLICATION LAYER • Hardware used: Application Gateway • Protocol used: HTTP, SMTP, POP3, FTP, Telnet, etc. • Data unit: Data
  24. 24. THANK YOU!!!