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6-OSI Model - ISO - Organization for Standardization.
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- 3. 3 OSI meansOpen System Interconnect model. Developed by the International Organization for Standardization in 1974. It consists of seven layers. Each layer has a different but specific processing function. OSI Model
- 4. ISO - Organizationfor Standardization. International standards organisation is responsible for a wide range of standards, including many that are relevant to computer networking. In 1984 , the Open Systems Interconnection (OSI) Reference Model was approved as an international standard for communications architecture.
- 5. Figure. Tasks involvedin sending a letter
- 6. 6 Advice Person Sales Take Not Do Please OSI Model Layers Application Presentation Session Transport Network DataLink Physical Layer - 7 Layer - 6 Layer - 5 Layer - 4 Layer - 3 Layer - 2 Layer - 1 Upper Layer or Software Layer Lower Layer or Hardware Layer Heart of OSI
- 7. 7 Application Layer Application Layeris responsible for providing Networking Services to user. It also known as Desktop Layer. Identification of Services is done using Port Numbers. e.g. HTTP,FTP, SMTP, SIP,IMAP,DNS Ports are nothing but Socket i.e. Entry and Exit Point to the Layer Total No. Ports 0 – 65535 Reserved Ports 0 – 1023 Open Ports 1024 – 65535 Application Presentation Session Transport Network Data Link Physical Application
- 8. 8 Examples of NetworkingServices Service Port No. HTTP 80 FTP 21 SMTP 25 TELNET 23 TFTP 69
- 9. 9 Example of FTPrequest Client FTP Server ftp://ftp.microsoft.com
- 10. 10 Example of FTPrequest FTP Request ftp://ftp.microsoft.com FTP Request Listen on Port 21 Sending FTP Reply Received FTP Reply ftp://ftp.microsoft.com Client FTP Server
- 11. 11 Application 21 80 25 67 5369 How data flows from Application Layer Data Presentation Session Transport Network Data Link Physical
- 12. 12 Presentation Layer Presentation Layeris responsible for converting data into standard format. Examples : ASCII, EBCDIC, JPEG, MPEG, BMP, MIDI, WAV, MP3 Following tasks are perform at Presentation layer : Encoding – Decoding Encryption – Decryption Compression – Decompression Application Presentation Session Transport Network Data Link Physical Presentation
- 13. 13 How data flowsfrom Presentation Layer Data Data Application Presentation Session Transport Network Data Link Physical
- 14. 14 Session Layer Session Layeris responsible establishing, maintaining and terminating session. Session ID also works at Session Layer. Application Presentation Session Transport Network Data Link Physical Session
- 15. 15 How data flowsfrom Session Layer Data Data Data Application Presentation Session Transport Network Data Link Physical
- 16. 16 Transport Layer Transport Layeris responsible for end-to-end connectivity. It is also known as heart of OSI Layers. Following task are performed at Transport Layer : - • Identifying Service • Multiplexing & De-multiplexing • Segmentation • Sequencing & Reassembling • Flow Control • Error Detection Application Presentation Session Transport Network Data Link Physical Transport
- 17. 17 Identifying Service • TransmissionControl Protocol • Connection Oriented • Acknowledgement • Reliable • Slower • Port No. 6 • e.g. HTTP, FTP, SMTP • User Datagram Protocol • Connection Less • No Acknowledgement • Unreliable • Faster • Port No. 17 • e.g. DNS, DHCP, TFTP,SNMP TCP UDP
- 18. 18 Application Presentation Session Multiplexing & De-multiplexing 21 8025 67 53 69 Transport TCP - 6 UDP - 17 Network Data Link Physical
- 19. 19 Segmentation Hello! How areyou ? Hello! How Are You ? Hello! How are you ? A B
- 20. 20 Sequencing & Reassembling Hello!How are you ? Hello! 1/5 How 2/5 Are 3/5 You 4/5 ? 5/5 Hello! How are you ? A B Hello! How are you ? Hello! 1/5 How 2/5 Are 3/5 You 4/5 ? 5/5 Hello! 1/5 How 2/5 Are 3/5 You 4/5 ? 5/5 Hello! How are you ?
- 21. 21 Error Detection Hello! Howare you ? Hello! 1/5 How 2/5 Are 3/5 You 4/5 ? 5/5 Hello! How are you ? Hello! 1/5 Are 3/5 You 4/5 ? 5/5 Hello! 1/5 Are 3/5 You 4/5 ? 5/5 Segment Missing Hello! 1/5 Are 3/5 You 4/5 ? 5/5 How 2/5 How 2/5 Hello! How are you ? Hello! How are you ? A B
- 22. 22 Flow Control -Windowing Sending 3-window Received 3-window Ack-Rec- 3 Sending 5-window Received 4-window A B Ack. Received- 4 PC-A can send 4 Segment at a time to PC-B
- 23. 23 How data flowsfrom Transport Layer Data Data Data Data TH Segment Application Presentation Session Transport Network Data Link Physical
- 24. 24 Network Layer Network Layeris responsible for providing best path to data to reach destination. Logical Addressing sits on this layer. Device working on Network Layer is Router. It is divided into two parts • Routed Protocols e.g. IP, IPX, Apple Talk. • Routing Protocols e.g. RIP, IGRP, OSPF, EIGRP Application Presentation Session Transport Network Data Link Physical Network
- 25. 25 Routed Protocols 192.168.1.1 192.168.1.2 AB Segment Segment Source IP 192.168.1.1 Destination IP 192.168.1.2 Source IP 192.168.1.1 Destination IP 192.168.1.2 Segment Hello! How are you ? Hello! How are you ?
- 26. 26 How data flowsfrom Network Layer Data Data Data Segment Segment NH e.g. Router Packet Application Presentation Session Transport Network Data Link Physical
- 27. 27 Datalink Layer Data linkLayer is divided into two Sub Layers : • LLC – Logical Link Control It talks about Wan protocols e.g. PPP, HDLC, Frame-relay • MAC – Media Access Control It talks about Physical Address. It is 48 bit Addressing i.e. 12 digit Hexadecimal No. It is also responsible for Error Detection Device working on Data Link Layer is Switch, Bridge, NIC. Application Presentation Session Transport Network Data Link Physical Data Link
- 28. 28 Error Detection –CRC Check Hello! How are you ? Packet Packet Source MAC 00-20-18-C0-07-71 Destination MAC 00-20-18-C0-07-72 00000 32434 22222 89696 55434 99323 43434 99434 46323 11114 33333 00000 32434 22222 89696 55434 99323 43434 99434 46323 11114 Error Detected 192.168.1.1 00-20-18-C0-07-71 192.168.1.2 00-20-18-C0-07-72 A B PC-A CRC No. 33333 PC-B CRC No. 11114 Error Detected For Error Correction Contact Source Transport layer
- 29. 29 e.g. Switch How dataflows from Data Link Layer Data Data Data Segment DH Packet DT Application Presentation Session Transport Network Data Link Physical Packet Packet Frame
- 30. 30 Physical Layer Physical Layeris responsible for electrical, mechanical or procedural checks. Data will be converted in Binary that is 0’s & 1’s. Data will be in the form of electrical pulses if it is Coaxial or Twisted Pair cable and in the form of Light if it is Fiber Optic Cable. Devices working at Physical Layer are Hubs, Repeaters, Cables, Modems etc. Application Presentation Session Transport Network Data Link Physical Physical
- 31. 31 Physical Layer Example Frame Frame 1010101010101010 1010101010101010 Hello! Howare you ? A B 0101011010101010101010101 1010101101010101010101010 0101011010101010101010101 1010101101010101010101010 0101011010101010101010101 Frame
- 32. 32 How data flowsfrom Physical Layer Data Data Data Segment Packet Frame Bits e.g. Hub Application Presentation Session Transport Network Data Link Physical
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- 34. Layers of OSIReference Model.
- 35. 35 Segment Packet Frame A B Packet Data Data Data Bits Data Segment Data Encapsulation& De-capsulation Packet Data Data Data Application Presentation Session Transport Network Data Link Physical Application Presentation Session Transport Network Data Link Physical Bits DH DT NH TH Segment Packet DT Packet DH DT DH NH Segment NH TH Data TH Frame Packet
- 36. 36 Application Transport Internet Network Access Comparing OSI withTCP/IP Layers OSI Layers TCP/IP Layers Application Presentation Session Transport Network Data Link Physical
- 37. OSI Layers (1) Physical Bottommost layer Implements an unreliable bit link Uses synchronization bits to synchronize the receiver Specify the modulation scheme Physical interface between devices Mechanical Electrical Functional Procedural For activating, maintaining and deactivating the physical link between communicating network systems
- 38. Data Link Layer. The data link layer is responsible for moving frames from one hop (node) to the next. The major duties of the data link layer are: Framing Physical addressing: Physical address is the MAC address, which is hard coded into NIC and is of 48-bit represented by Hexadecimal format. 00.27.AB.CC.EE.23 00.27.AB-Vendor CC.EE.23-User Cmd Ipconfig/all to show the system details Flow control Error Control Access Control Data Link layer protocols are CSMA/CD, CSMA/CA, Token passing etc.
- 39. OSI Layers (2) Data Link Supervises transmission of packets by physical layer Means of activating, maintaining and deactivating a reliable link Adds sequence number and CRC Error detection and control Encapsulation and Decapsulation are performed Regulates the access to the link Higher layers may assume error free transmission A) Medium Access Control MAC address will be added B) Logical Link Control CRC will be added
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- 42. Network Layer. Thenetwork layer is responsible for the source -to- destination delivery of a packet possibly across multiple networks. It two systems are connected to the same link, there is usually no need for a network layer. However, if the two systems are attached to different networks with connecting devices between the networks, there is need for the network layer to accomplish the delivery. The major duties performed by the network layer are:
- 43. Network Layer. Logicaladdressing: Logical address is also called IP address which is of 32-bits and represented in decimal format. 192.168.32.97 Routing: To route the packets from the source to destination in an internetwork, the router uses network layer information. The PDU of network layer is packet. Network layer protocols are IP, IPX, AppleTalk. Routing protocol-RIP , OSPF, BGP Routed Protocol - IP, IPX, AppleTalk
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