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Chap. 2 Network Models

Chap. 2 Network Models. 2.1 Layered Tasks. Sender, Receiver and Carrier. Layered Tasks. Hierarchy Higher Layer Middle Layer Lower Layer Services The Each layer uses the services of the layer immediately below it. 2.2 Internet Model. Five Layer Internet Model. Internet Model.

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Chap. 2 Network Models

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  1. Chap. 2Network Models

  2. 2.1 Layered Tasks • Sender, Receiver and Carrier

  3. Layered Tasks • Hierarchy • Higher Layer • Middle Layer • Lower Layer • Services • The Each layer uses the services of the layer immediately below it.

  4. 2.2 Internet Model • Five Layer Internet Model

  5. Internet Model • Peer-to-peer Processes

  6. Peer-to-peer Processes • Interfaces between Layers • Each interface defines what information and services a layer must provide for the layer above it. • Well defined interfaces and layer functions provide modularity to a network • Organizations of the layers • Network support layers : Layers 1, 2, 3 • User support layer : Layer 5 • It allows interoperability among unrelated software systems • Transport layer (Layer 4) : linking two subgroups

  7. Peer-to-peer Processes • An exchange using the Internet model

  8. Physical Layer • coordinates the functions required to transmit a bit stream over a physical medium. (deal with the mechanical and electrical specification of the primary connections: cable, connector) • Physical characteristics of interfaces and media • Representation of bits • Data rate : transmission rate • Synchronization of bits  is responsible for transmitting individual bits from one node to the next node

  9. Physical Layer

  10. Data Link Layer • The data link layer is responsible for transmitting frames from one node to the next.

  11. Data Link Layer • Major duties • Framing • Physical addressing • Flow control • Error control • Access control

  12. Data Link Layer • Hop-to-hop (node-to-node) delivery

  13. Data Link Layer In Figure 2.8 a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link. At the data link level this frame contains physical addresses in the header. These are the only addresses needed. The rest of the header contains other information needed at this level. The trailer usually contains extra bits needed for error detection

  14. Network Layer • The network layer is responsible for the delivery of packets from the original source to the final destination.

  15. Network Layer • Logical addressing • Routing

  16. Network Layer

  17. Transport Layer

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

  19. Transport Layer • Port addressing • Segmentation and ressemblt • Connection control • Flow control • Error control

  20. Transport Layer

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

  22. Application Layer • The major duties of the application • Mail services • File transfer and access • Remote log-in • Accessing the World Wide Web

  23. Summary of Layers

  24. 2.3 OSI Model

  25. OSI Reference Model • OSI : Open System Interconnection by ISO • Basic Reference Model : ISO-7498 • Purpose of OSI Model ~ is to open communication between different systems without requiring changes to the logic of the underlying hardware and software.

  26. The Model • OSI Model ~ is layered framework for the design of network systems that allows for communication across all types of computer systems • Layered Architecture ~ shows the layers involved when a message is sent from device A to device B

  27. Model (cont’d) • The OSI Model

  28. OSI Layers

  29. Model (cont’d) • Peer-to-peer process ~ process on each machine that communicate at a given layer • Interfaces between Layers ~ defines what information and services a layer must provide for the layer above it

  30. Applications for All Layers

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