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Network Models

Kingdom of Saudi Arabia Prince Norah bint Abdul Rahman University College of Computer Since and Information System NET331. Network Models. T.Najah Al_Subaie. Chapter 2. LAYERED TASKS OSI Model TCP/IP Model. Layered Tasks.

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Network Models

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  1. Kingdom of Saudi Arabia • Prince Norah bint Abdul Rahman University • College of Computer Since and Information System • NET331 Network Models T.NajahAl_Subaie

  2. Chapter 2 • LAYERED TASKS • OSI Model • TCP/IP Model

  3. Layered Tasks • We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. • The process of sending a letter to a friend would be complex if there were no services available from the post office.

  4. Tasks Involved in Sending a Letter

  5. The OSI Model • Established in 1947, • the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. • An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. • It was first introduced in the late 1970s.

  6. Note • ISO is the organization. • OSI is the model.

  7. Seven layers of the OSI model

  8. The OSI Model • ISO model is not a protocol. It is a model for understanding and designing a network architecture. • It shows how to facilitate communication between different system without requiring changes to the logic of the underlying hardware and software.

  9. The OSI Model • It is a layered framework for the design of network systems that allows communication between all types of computer systems. • Consists of seven separated but related layers. • Each layer defines a part of the process of moving information across a network

  10. Layered Architecture • Each layer groups the networking functions that had related uses. • Each layer uses the services provided by the layer just below it. • Between machines, the corresponding layers are communicated using a set of protocols. • Peer to Peer processes.

  11. The interaction between layers in the OSI model

  12. The philosopher-translator-secretary architectu

  13. Interfaces Between Layers • Each interface defines the information and services a layer must provide for the layer above it. • Interfaces allows the specific implementation of the layer’s functionality to be changed or replaced without requiring changes to the surrounding layers.

  14. An exchange using the OSI model

  15. Organization of the Layer • At the sender: • each layer adds a header or possibly a trailer. • At the receiver: • each layer removes its corresponding header or trailer and performs the appropriate actions. • When the message reaches layer 7 (application layer) , the message is in a form appropriate to the applications.

  16. Encapsulation • The data portion of a packet at level N-1 carries the whole packet ( data and header/ trailer) from level N.

  17. Layers in the OSI Model. • We briefly describe the functions of each layer in the OSI model. • Physical Layer • Data Link Layer • Network Layer • Transport Layer • Session Layer • Presentation Layer • Application Layer

  18. Physical Layer • The physical layer is responsible for movements of individual bits from one hop (node) to the next.

  19. Physical Layer • It is also concerned with: • Physical characteristics of interfaces and medium. • Representation of bits. • Data rate. • Synchronization of bits. • Line configuration. • Physical topology. • Transmission mode.

  20. Data Link Layer • The data link layer (DLL) is responsible for moving frames from one hop (node) to the next.

  21. Data Link Layer

  22. Data Link Layer • It is also concerned with: • Framing. • Data units in DLL. • Physical addressing • Adding header to define header/receiver of the frame. • Flow control • To avoid overwhelming the receiver. • Error control • A set of mechanisms to keep a reliable transmission. • Access control • To control the traffic in the link.

  23. Hop-to-hop delivery by the DLL

  24. Network Layer • The network layer is responsible for the delivery of individual packets from the source host to the destination host.

  25. Network Layer

  26. Source-to-Destination Delivery

  27. Transport Layer • The transport layer is responsible for the delivery of a message from one process to another.

  28. Transport Layer

  29. Transport Layer • It is also concerned with: • Service point addressing. • Segmentation and reassembly. • Connection control. • Flow control. • Error control.

  30. Process to Process Delivery by the Transport Layer

  31. Session Layer • The session layer is responsible for dialog control and synchronization. • Its functionalities: • Dialog control. • Synchronization.

  32. Session Layer

  33. Presentation Layer • The presentation layer is responsible for translation, compression, and encryption.

  34. Presentation Layer

  35. Application Layer • The application layer is responsible for providing services to the user.

  36. Application Layer

  37. Summary of Layers

  38. TCP/IP Reference Model • the TCP/IP protocol suite is made of five layers: • physical, • data link, • network, • transport, • application.

  39. TCP/IP and OSI model

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