Uploaded byMujmmil Shaikh
OSI REFRENCE MODEL by- Mujmmil Shaikh
The document outlines the OSI reference model, which is essential for understanding layered communication in networking. It describes seven layers that facilitate complex communication functionalities, such as application services, data representation, and reliable data transport. Additionally, it distinguishes between host layers that ensure data delivery and media layers that manage the physical aspects of data transmission.
OSI REFRENCE MODEL by- Mujmmil Shaikh
- 2. The Layered Model ©1999, Cisco Systems, Inc. www.cisco.com
- 3. Layered Communication Location A Ik hou Message van konijnen L: EN Information for the I like Remote rabbits Translator Fax #:--- Information L: EN for the I like Remote rabbits Secretary Source: Tanenbaum, 1996
- 4. Layered Communication Location A Location B Ik hou J’aime Message van les lapins konijnen L: EN Information L: EN for the I like I like Remote rabbits Translator rabbits Fax #:--- Fax #:--- Information L: EN L: EN for the I like I like Remote rabbits Secretary rabbits
- 5. Layered Communication Location A Location B Layers Ik hou J’aime van Message 3 les lapins konijnen L: EN Information L: EN I like for the remote 2 I like rabbits rabbits translator Fax #:--- Fax #:--- Information L: EN L: EN for the I like I like remote rabbits secretary 1 rabbits
- 6. Why a LayeredNetwork Model? 7 Application • Reduces complexity (one big problem to seven smaller ones) 6 Presentation • Standardizes interfaces 5 Session • Facilitates modular engineering 4 Transport • Assures interoperable technology 3 Network • Accelerates evolution 2 Data Link • Simplifies teaching and learning 1 Physical
- 7. Devices Function atLayers 7 Application 6 Presentation NIC Card 5 Session 4 Transport 3 Network 2 Data Link 1 Physical Hub
- 8. Host Layers } 7 Application 6 Presentation Host layers: Provide accurate 5 Session data delivery between computers 4 Transport 3 Network 2 Data Link 1 Physical
- 9. Media Layers } 7 Application 6 Presentation Host layers: Provide accurate 5 Session data delivery between computers 4 Transport } 3 Network 2 Data Link Media layers: Control 1 Physical physical delivery of messages over the network
- 10. Layer Functions 7 Application Provides network services to application processes (such as electronic mail, file transfer, and terminal emulation)
- 11. Layer Functions 7 Application Network services to applications 6 Presentation Data representation • Ensures data is readable by receiving system • Format of data • Data structures • Negotiates data transfer syntax for application layer
- 12. Layer Functions 7 Application Network services to applications 6 Presentation Data representation 5 Session Inter-host communication • Establishes, manages, and terminates sessions between applications
- 13. Layer Functions 7 Application Network services to applications 6 Presentation Data representation 5 Session Inter-host communication 4 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
- 14. Layer Functions 7 Application Network services to applications 6 Presentation Data representation 5 Session Inter-host communication 4 Transport End-to-end connection reliability 3 Network Addresses and best path • Provides connectivity and path selection between two end systems • Domain of routing
- 15. Layer Functions 7 Application Network services to applications 6 Presentation Data representation 5 Session Inter-host communication 4 Transport End-to-end connection reliability 3 Network Addresses and best path 2 Data Link Access to media • Provides reliable transfer of data across media • Physical addressing, network topology, error notification, flow control
- 16. Layer Functions 7 Application Network services to applications 6 Presentation Data representation 5 Session Inter-host communication 4 Transport End-to-end connection reliability 3 Network Addresses and best path 2 Data Link Access to media 1 Physical Binary transmission • Wires, connectors, voltages, data rates
- 17. Peer-to-Peer Communications Host A Host B 7 Application Application 6 Presentation Presentation 5 Session Session 4 Transport Segments Transport 3 Network Packets Network 2 Data Link Frames Data Link 1 Physical Bits Physical
- 18. Data Encapsulation Host A Host B Application Application Presentation Session Transport } { Data Presentation Session Transport Network Network Data Link Data Link Physical Physical
- 19. Data Encapsulation Host A Host B Application Application Presentation Session Transport } { Data Network Data Header Presentation Session Transport Network Network Data Link Data Link Physical Physical
- 20. Data Encapsulation Host A Host B Application Application Presentation Session Transport } { Data Network Data Header Presentation Session Transport Network Network Frame Network Data Frame Data Link Data Link Header Header Trailer Physical Physical
- 21. Data Encapsulation Host A Host B Application Application Presentation Session Transport } { Data Network Data Header Presentation Session Transport Network Network Frame Network Data Frame Data Link Data Link Header Header Trailer Physical Physical 0101101010110001
- 22. Layers 1 &2: Physical & Data Link Layers © 1999, Cisco Systems, Inc. www.cisco.com
- 23. Physical and LogicalAddressing 0000.0c12.3456
- 24. 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
- 25. Layer 3: Network Layer © 1999, Cisco Systems, Inc. www.cisco.com
- 26. Network Layer: PathDetermination Which Path? Which Path? • Layer 3 functions to find the best path through the internetwork
- 27. Network Layer: CommunicatePath 5 2 9 6 8 4 10 11 1 3 7 Addresses represent the path of media connections Routing helps contain broadcasts
- 28. Addressing—Network and Node Network Node 1 1 2.1 2 3 1.2 2 1 1.3 1.1 3.1 3 1 • Network address—Path part used by the router • Node address—Specific port or device on the network
- 29. Protocol Addressing Variations General Network Node Example 1 1 Network Host TCP/IP Example 10. 8.2.48 (Mask 255.0.0.0) Network Node Novell IPX Example 1aceb0b. 0000.0c00.6e25
- 30. Network Layer Protocol Operations X Y C C A A Each router provides its services to support upper layer functions
- 31. Network Layer Protocol Operations X Y C C A A B B Host X Host Y Application Application Presentation Presentation Session Router A Router B Router C Session Transport Transport Network Network Network Network Network Data Link Data Link Data Link Data Link Data Link Physical Physical Physical Physical Physical Each router provides its services to support upper layer functions
- 32. Routed Versus RoutingProtocol • Routed protocol used between routers to direct user traffic Examples: IP, IPX, AppleTalk, DECnet Network Destination Exit Port Protocol Network to Use Protocol Name 1.0 1.1 2.0 2.1 3.0 3.1
- 33. Routed Versus RoutingProtocol • Routed protocol used between routers to direct user traffic Examples: IP, IPX, AppleTalk, DECnet • Routing protocol used only between routers to maintain routing tables Examples: RIP, IGRP, OSPF
- 34. Static Versus DynamicRoutes Static Route Uses a protocol route that a network administrator enters into the router Dynamic Route Uses a route that a network protocol adjusts automatically for topology or traffic changes
- 35. Static Route Example Point-to-point or A A circuit-switched connection Only a single network connection with no need B B for routing updates ―Stub‖ network Fixed route to address reflects administrator’s knowledge
- 36. Adapting to TopologyChange A A B B D D C C Can an alternate route substitute for a failed route?
- 37. Adapting to TopologyChange A A B B X D D C C
- 38. Adapting to TopologyChange A A B B X D D C C Can an alternate route substitute for a failed route? Yes—With dynamic routing enabled
- 39. Layers 4–7: Transport, Session, Presentation, and Application Layers © 1999, Cisco Systems, Inc. www.cisco.com
- 40. Transport Layer Segments upper-layer applications Establishes an end-to-end connection Sends segments from one end host to another Optionally, ensures data reliability
- 41. Transport Layer— Segments Upper-Layer Applications Application Electronic File Terminal Presentation Mail Transfer Session Session Transport Application Application Data Data Port Port Segments
- 42. Transport Layer— Establishes Connection Sender Receiver Synchronize Negotiate Connection Synchronize Acknowledge Connection Established Data Transfer (Send Segments)
- 43. Transport Layer— Sends Segmentswith Flow Control Transmit Sender Receiver Buffer Full Not Ready Stop Process Segments Go Ready Buffer OK Resume Transmission
- 44. Transport Layer— Reliability with Windowing • Window Size = 1 Send 1 Receive 1 Ack 2 Sender 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
- 45. Transport Layer— An Acknowledgement Technique Sender Receiver 1 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
- 46. Transport to NetworkLayer End-to-End Segments Routed Packets
- 47. Session Layer • Network File System (NFS) • Structured Query Language (SQL) • Remote-Procedure Call (RPC) • X Window System • AppleTalk Session Protocol (ASP) • DEC Session Control Protocol (SCP) Service Request Service Reply Coordinates applications as they interact on different hosts
- 48. Presentation Layer • Text • Graphics • Data • Visual images ASCII PICT login: EBCDIC TIFF Encrypted JPEG • Sound GIF MIDI • Video MPEG QuickTime Provides code formatting and conversion for applications
- 49. 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) Others Internetwork applications can extend beyond the enterprise (i.e., to suppliers, etc.)
- 50. 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