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Network Fundamentals

OSI Communications M odel . Network Fundamentals. OSI Communications model. Open System Interconnection Reference Model Organizes services into layers A layer is a set of services that provide services to layers above and receive services from layers below.

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Network Fundamentals

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  1. OSI Communications Model Network Fundamentals

  2. OSI Communications model • Open System Interconnection Reference Model • Organizes services into layers • A layer is a set of services that provide services to layers above and receive services from layers below. • Allows for protocols to be coded at one layer without having to worry about handling lower layers.

  3. OSI Model Breakdown Source: http://en.wikipedia.org/wiki/OSI_model

  4. Layer 1: Physical Layer • Defines the layout of pins, voltages, cable specifications, hubs, repeaters, network adapters, Host Bus Adapters, etc. • The physical layer deals with the communication of one device to the medium.

  5. Layer 1: Physical Layer • Major functions: • Establishing and terminating a connection to the medium. • Flow control • Modulation, the conversion between the digital data and the signals sent over the medium. This can be done over physical cables (copper, fiber) or over radio.

  6. Layer 2: Data Link Layer • Transfers data between adjacent nodes on a WAN (Wide Area Network) or between nodes on the same local LAN (Local Area Network) • Outside of those boundaries the data is handed off to a higher layer for transfer.

  7. Layer 2: Data Link Layer • Layer 2 services: • Error control • Flow control • Layer 2 error and flow control are not used in LAN protocols like Ethernet, but areused in modems, and wireless networks • Physical addressing (MAC) • Packet switching

  8. Layer 3: Network Layer • Provides a means to transfer variable length data from a source to a destination via one or more networks. • Routing is preformed on this layer. • Best known Layer 3 protocol is IP (Internet Protocol)

  9. Layer 4: Transport Layer • Controls flow control, segmentation/desegmentation, and error control. • Best known protocols are TCP (Transmission Control Protocol) and UDP (User Datagram Protocol)

  10. Layer 5: Session Layer • Manages the connections between computers. • Establishes, manages and terminates connections. • Allows for full-duplex, half-duplex, or simplex operation.

  11. Layer 6: Presentation Layer • Deals with the delivery and formatting of information given to the application layer. • Examples: ASCII, UTF8, SSL, MIME

  12. Layer 7: Application Layer • Provide ways for applications to communicate with the lower layers. • Examples: HTTP (Hyper Text Transfer Protocol), FTP (File Transfer Protocol)

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