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Lecture W3 CN Helping Notes_network models

Helping Notes_network models

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Lecture W3 CN Helping Notes_network models

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  1. Network Models Engr. Gohar Mumtaz Lecturer, Superior University, Lahore gohar.m@superior.edu.pk

  2. Outline • What is a Network? • Network Reference Models • Open Systems Interconnection (OSI) Model • The Upper Layers • The Lower Layers • OSI Model Example • Department of Defense (DoD) Model • Conclusion • References

  3. What is a Network? • Α NETWORK is simply defined as something that connects things together for a specific purpose. • The term network is used in a variety of contexts, including telephone, television, computer, or even people networks. • A COMPUTER NETWORK connects two or more devices together to share information and services, including • Websites • Email and messaging

  4. Network Reference Models • Internetwork • Internetworking present challenges • interoperating between products from different manufacturers requires consistent standards • The two most recognized network reference models are: • The Open Systems Interconnection (OSI) model • The Department of Defense (DoD) model

  5. Open Systems Interconnection (OSI) Model

  6. OSI Model • International Standards Organization (ISO) • Formalized in 1984

  7. OSI Model… Easy to REMEMBER!

  8. Upper Layers • Also known as User Support Layers • Manage application-level functions • Implemented in Software

  9. Application Layer • Provides the interface between the user application and the network • Examples of Application layer protocols • FTP, via an FTP client • HTTP, via a web browser • POP3 and SMTP, via an email client • Telnet • Provides a variety of functions: • Identifies communication partners • Determines resource availability • Synchronizes communication

  10. Presentation Layer • Controls the formatting and syntax of user data for the application layer • Examples of Presentation layer formats • Text - RTF, ASCII, EBCDIC • Images - GIF, JPG, TIF • Audio - MIDI, MP3, WAV • Movies - MPEG, AVI, MOV • Provides a variety of functions: • Encryption, Decryption • Compression, Decompression

  11. Session Layer • Responsible for establishing, maintaining, and ultimately terminating sessions between devices • Sessions communication falls under one of three categories: • Full-Duplex – simultaneous two-way communication • Half-Duplex – two-way communication, but not simultaneous • Simplex – one-way communication

  12. Lower Layers • Control end-to-end transport of data between devices • Implemented in Software & Hardware • Layer 1, Layer 2, Layer3 are also known as Network Support Layers

  13. Transport Layer • Responsible for the reliable transfer of data • Transport layer communication falls under two categories: • Connection-oriented – requires that a connection with specific agreed-upon parameters be established before data is sent. • Connectionless – requires no connection before data is sent. • Transport layer protocols: • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP)

  14. Network Layer • Controls internetwork communication, and has two key responsibilities: • Logical addressing – provides a unique address that identifies both the host, and the network that host exists on. • Routing – determines the best path to a particular destination network, and then routes data accordingly. • The most common Network layer protocol: • Internet Protocol (IP)

  15. Data-Link Layer • Responsible for transporting data within a network • The Data-Link layer consists of two sublayers: • Logical Link Control (LLC) sublayer • Media Access Control (MAC) sublayer • Datalink layer technologies: • Ethernet uses CSMA/CD • Token Ring uses Token • Functions: • Framing or Encapsulation • MAC or CAM or Physical or Hardware Address

  16. Physical Layer • Controls the signaling and transferring of raw bits onto the physical medium • The Physical layer provides specifications for a variety of hardware • Cabling • Connectors and transceivers • Network interface cards (NICs)

  17. OSI Model Example

  18. Web Browser Example • The web browser serves as the user interface for accessing a website. The web browser invokes the Hyper Text Transfer Protocol (HTTP) (Application Layer) to interface with the remote web server, which is why http:// precedes every web address. • The Internet can provide data in a wide variety of formats, a function of the Presentation layer. Common formats on the Internet include HTML, XML, PHP, GIF, and JPEG. • The Session layer is responsible for establishing, maintaining, and terminating the session between devices, and determining whether the communication is half-duplex or full-duplex.

  19. Web Browser Example… • HTTP utilizes the TCP Transport layer protocol to ensure the reliable delivery of data. • The best path to route the data between the client and the web server is determined by IP, a Network layer protocol. • Data cannot be sent directly to a logical address. As packets travel from network to network, IP addresses are translated to hardware addresses, which are a function of the Data-Link layer. • The data is finally transferred onto the network medium at the Physical layer, in the form of raw bits.

  20. Department of Defense (DoD) Model

  21. DoD Model • Also known as TCP/IP Model • Consists of Four Layers

  22. DoD Model • The following chart illustrates where common protocols fit into the DoD model:

  23. Conclusion • Despite the practicality of the DoD model, the OSI model is still the basis for most network terminology. So, Please Do Not Throw Sausage Pizza Away. ☺

  24. References… [1] “Data Communications and Networking” 4th Edition by Behrouz A. Forouzan [2] CCNA Study Guide v2.71 – Aaron Balchunas

  25. Any Question

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