OSI Reference Model       www.cisco.com   © 1999, Cisco Systems, Inc.
Тойм• The Layered Model• Layers 1 & 2: Physical &  Data Link Layers• Layer 3: Network Layer• Layers 4–7: Transport,  Sessi...
Хэрхэн цээжлэх вэ?All          - ApplicationPeople       - PresentationSeems        - SessionTo           - TransportNeed ...
The Layered Model© 1999, Cisco Systems, Inc.   www.cisco.com   © 1999, Cisco Systems, Inc.
Why a Layered Network Model? 7   Application    • Нарийн төвөгтэй байдлыг                      багасгасан (нэг гол асуудал...
Давхарга бүр дэхь           төхөөрөмжүүдийн үүрэг            7   Application            6   PresentationNIC Card          ...
Эзэмшигч давхаргууд                   }7   Application6   Presentation       Host layers: Өгөгдлийг                       ...
Зөөврийн давхаргууд                   }7   Application6   Presentation       Host layers: Өгөгдлийг5   Session            ...
Application Layer7   Application   Хэрэглээний програмуудын                  сүлжээний орчинд найдвартай                  ...
Presentation Layer7   Application    Хэрэглээний програмын сүлжээн                   дэхь үйлчилгээ6   Presentation   Өгөг...
Session Layer7   Application    Хэрэглээний програмын сүлжээн                   дэхь үйлчилгээ6   Presentation   Өгөгдлийн...
Transport Layer7   Application    Network services to applications6   Presentation   Data representation5     Session     ...
Network Layer7   Application    Network services to applications6   Presentation   Data representation5     Session      I...
Data Link Layer7   Application    Network services to applications6   Presentation   Data representation5     Session     ...
Physical Layer7   Application    Network services to applications6   Presentation   Data representation5     Session      ...
Communications      Host A                     Host B7   Application               Application6   Presentation            ...
Data Encapsulation  Host A                           Host BApplication                    ApplicationPresentationSessionTr...
Data Encapsulation  Host A                             Host BApplication                        ApplicationPresentationSes...
Data Encapsulation  Host A                                           Host BApplication                                    ...
Data Encapsulation  Host A                                           Host BApplication                                    ...
Layers 1 & 2:Physical & Data Link      Layers        www.cisco.com   © 1999, Cisco Systems, Inc.
MAC Address           24 bits          24 bits      Vendor Code      Serial Number          0000.0c12. 3456               ...
Layer 3:                              Network Layer© 1999, Cisco Systems, Inc.       www.cisco.com   © 1999, Cisco Systems...
Network Layer: Path Determination                  Which Path?                  Which Path?    • Layer 3 functions to find...
Layers 4–7:Transport, Session, Presentation, andApplication Layers       www.cisco.com   © 1999, Cisco Systems, Inc.
Transport Layer•   Segments upper-layer applications•   Establishes an end-to-end connection•   Sends segments from one en...
Transport Layer—    Establishes ConnectionSender                                 Receiver          Synchronize            ...
Transport Layer—Sends Segments with Flow Control               Transmit  Sender                                Receiver   ...
Transport Layer—         Reliability with Windowing                    • Window Size = 1           Send 1                 ...
Transport Layer—An Acknowledgement Technique       Sender     Receiver1 2 3 4 5 6 7   1 2 3 4 5 6 7       Send 1       Sen...
Transport to Network Layer       End-to-End Segments           Routed Packets
Session Layer  •   Network File System (NFS)  •   Structured Query Language (SQL)  •   Remote-Procedure Call (RPC)  •   Ap...
Presentation Layer         •   Text                        •   Graphics         •   Data                        •   Visual...
Application Layer   COMPUTER  APPLICATIONS             NETWORK Word Processor          APPLICATIONS               INTERNET...
Summary• OSI reference model describes building  blocks of functions for program-to-  program communications between  simi...
Лекц 2
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Лекц 2

  1. 1. OSI Reference Model www.cisco.com © 1999, Cisco Systems, Inc.
  2. 2. Тойм• The Layered Model• Layers 1 & 2: Physical & Data Link Layers• Layer 3: Network Layer• Layers 4–7: Transport, Session, Presentation, and Application Layers
  3. 3. Хэрхэн цээжлэх вэ?All - ApplicationPeople - PresentationSeems - SessionTo - TransportNeed of - NetworkData - Data LinkProcessing - Physical
  4. 4. The Layered Model© 1999, Cisco Systems, Inc. www.cisco.com © 1999, Cisco Systems, Inc.
  5. 5. Why a Layered Network Model? 7 Application • Нарийн төвөгтэй байдлыг багасгасан (нэг гол асуудал 6 Presentation нь 7-н жижиг one big problem 5 Session to seven smaller ones) • Интерфейсийг стандартад 4 Transport оруулсан 3 Network • Заах ба суралцахад хялбар 2 Data Link болсон 1 Physical
  6. 6. Давхарга бүр дэхь төхөөрөмжүүдийн үүрэг 7 Application 6 PresentationNIC Card 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Hub
  7. 7. Эзэмшигч давхаргууд }7 Application6 Presentation Host layers: Өгөгдлийг компьютераас компьютер5 Session лүү алдаагүй дамжуулалтыг4 Transport хангаж өгнө.3 Network2 Data Link1 Physical
  8. 8. Зөөврийн давхаргууд }7 Application6 Presentation Host layers: Өгөгдлийг5 Session компьютераас компьютер лүү алдаагүй дамжуулалтыг4 Transport хангаж өгнө. }3 Network2 Data Link Media layers: Мэдээг сүлжээнд дамжуулахад1 Physical физик хяналт тавина.
  9. 9. Application Layer7 Application Хэрэглээний програмуудын сүлжээний орчинд найдвартай ажиллагааг хангаж өгнө. (жнь:е-майл, файл дамжуулалт ба терминалд хувилгах )
  10. 10. Presentation Layer7 Application Хэрэглээний програмын сүлжээн дэхь үйлчилгээ6 Presentation Өгөгдлийн илэрхийлэл • Системээр хүлээн авсан өгөгдлийг ойлгомжтой байлгах баталгаагаар хангах • Өгөгдлийг форматлах • Өгөгдөл дамжуулахад холбоотой систем болох хэрэглээний давхаргатай тохиролцоно.
  11. 11. Session Layer7 Application Хэрэглээний програмын сүлжээн дэхь үйлчилгээ6 Presentation Өгөгдлийн илэрхийлэл5 Session Дундын эзэмшигчийн харилцан холбоо • Establishes, manages, and terminates sessions between applications
  12. 12. Transport Layer7 Application Network services to applications6 Presentation Data representation5 Session Inter-host communication4 Transport End-to-end connection reliability • Concerned with data transport issues between hosts • Data transport reliability • Establishes, maintains, and terminates virtual circuits • Fault detection and recovery • Information flow control
  13. 13. Network Layer7 Application Network services to applications6 Presentation Data representation5 Session Inter-host communication4 Transport End-to-end connection reliability3 Network Addresses and best path • Provides connectivity and path selection between two end systems • Domain of routing
  14. 14. Data Link Layer7 Application Network services to applications6 Presentation Data representation5 Session Inter-host communication4 Transport End-to-end connection reliability3 Network Addresses and best path2 Data Link Access to media • Provides reliable transfer of data across media • Physical addressing, network topology, error notification, flow control
  15. 15. Physical Layer7 Application Network services to applications6 Presentation Data representation5 Session Inter-host communication4 Transport End-to-end connection reliability3 Network Addresses and best path2 Data Link Access to media1 Physical Binary transmission • Wires, connectors, data rates
  16. 16. Communications Host A Host B7 Application Application6 Presentation Presentation5 Session Session Segments4 Transport Transport Packets3 Network Network Frames2 Data Link Data Link Bits1 Physical Physical
  17. 17. Data Encapsulation Host A Host BApplication ApplicationPresentationSessionTransportNetwork } { Data Presentation Session Transport NetworkData Link Data LinkPhysical Physical
  18. 18. Data Encapsulation Host A Host BApplication ApplicationPresentationSessionTransportNetwork } { Data Network Data Header Presentation Session Transport NetworkData Link Data LinkPhysical Physical
  19. 19. Data Encapsulation Host A Host BApplication ApplicationPresentationSessionTransportNetwork } { Data Network Data Header Presentation Session Transport Network Frame Network Data FrameData Link Data Link Header Header TrailerPhysical Physical
  20. 20. Data Encapsulation Host A Host BApplication ApplicationPresentationSessionTransportNetwork } { Data Network Data Header Presentation Session Transport Network Frame Network Data FrameData Link Data Link Header Header TrailerPhysical 0101101010110001 Physical
  21. 21. Layers 1 & 2:Physical & Data Link Layers www.cisco.com © 1999, Cisco Systems, Inc.
  22. 22. MAC Address 24 bits 24 bits Vendor Code Serial Number 0000.0c12. 3456 ROM RAM• MAC address is burned into ROM on a network interface card
  23. 23. Layer 3: Network Layer© 1999, Cisco Systems, Inc. www.cisco.com © 1999, Cisco Systems, Inc.
  24. 24. Network Layer: Path Determination Which Path? Which Path? • Layer 3 functions to find the best path through the internetwork
  25. 25. Layers 4–7:Transport, Session, Presentation, andApplication Layers www.cisco.com © 1999, Cisco Systems, Inc.
  26. 26. Transport Layer• Segments upper-layer applications• Establishes an end-to-end connection• Sends segments from one end host to another• Optionally, ensures data reliability
  27. 27. Transport Layer— Establishes ConnectionSender Receiver Synchronize Negotiate Connection Synchronize Acknowledge Connection Established Data Transfer (Send Segments)
  28. 28. Transport Layer—Sends Segments with Flow Control Transmit Sender Receiver Buffer Full Not Ready Stop Process Segments Go Ready Buffer OK Resume Transmission
  29. 29. Transport Layer— Reliability with Windowing • Window Size = 1 Send 1 Receive 1 Ack 2Sender Send 2 Receive 2 Receiver Ack 3 • Window Size = 3 Send 1 Receive 1 Send 2 Receive 2 Sender Send 3 Receive 3 Receiver Ack 4 Send 4
  30. 30. Transport Layer—An Acknowledgement Technique Sender Receiver1 2 3 4 5 6 7 1 2 3 4 5 6 7 Send 1 Send 2 Send 3 Ack 4 Send 4 Send 5 Send 6 Ack 5 Send 5 Ack 7
  31. 31. Transport to Network Layer End-to-End Segments Routed Packets
  32. 32. Session Layer • Network File System (NFS) • Structured Query Language (SQL) • Remote-Procedure Call (RPC) • AppleTalk Session Protocol (ASP) • DEC Session Control Protocol (SCP) Service Request Service Reply• Coordinates applications as they interact on different hosts
  33. 33. Presentation Layer • Text • Graphics • Data • Visual images ASCII PICTlogin: EBCDIC TIFF Encrypted JPEG • Sound GIF MIDI • Video MPEG QuickTime • Provides code formatting and conversion for applications
  34. 34. Application Layer COMPUTER APPLICATIONS NETWORK Word Processor APPLICATIONS INTERNETWORK Presentation Graphics Electronic Mail APPLICATIONS Spreadsheet File Transfer Electronic Data Interchange Database Remote Access World Wide Web Design/Manufacturing Client-Server Process E-Mail Gateways Project Planning Information Location Special-Interest Bulletin Boards Others Network Management Financial Transaction Services Others Internet Navigation Utilities Conferencing (Voice, Video, Data)• User Interaction Others
  35. 35. Summary• OSI reference model describes building blocks of functions for program-to- program communications between similar or dissimilar hosts• Layers 4–7 (host layers) provide accurate data delivery between computers• Layers 1–3 (media layers) control physical delivery of data over the network

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