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Hour 3

Hour 3. The Network Access Layer. What You'll Learn in This Hour:. Physical addresses Ethernet frames LAN technologies. Network Access Layer is the base of TCP/IP Model. Collection of services and specifications that provide and manage access to the network hardware.

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Hour 3

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  1. Hour 3 The Network Access Layer

  2. What You'll Learn in This Hour: • Physical addresses • Ethernet frames • LAN technologies

  3. Network Access Layer is the base of TCP/IP Model. • Collection of services and specifications that provide and manage access to the network hardware.

  4. This hour, you’ll be able to • Explain the Network Access layer • Discuss how TCP/IP's Network Access layer relates to the OSI networking model • Explain a network architecture • List the contents of an ethernet frame • Identify the methods that ethernet, token ring, and FDDI use for controlling access to the transmission medium

  5. Protocols and Hardware • The Network Access layer manages all the services and functions necessary to prepare the data for the physical network.

  6. The responsibilities include : • Interfacing with the computer's network adapter. • Coordinating the data transmission with the conventions of the appropriate access method. You'll learn more about access methods later in this hour. • Formatting the data into a unit called a frame and converting that frame into the stream of electric or analog pulses that passes across the transmission medium.

  7. (Cont) The responsibilities include : • Checking for errors in incoming frames. • Adding error-checking information to outgoing frames so that the receiving computer can check the frame for errors. • Acknowledging receipt of data frames and resending frames if acknowledgment is not received.

  8. There are many different types of Network Acess Layer for example • Ethernet • Token Ring • FDDI • PPP • Wireless Network

  9. The Network Access Layer and OSI Model • The Network Access Layer corresponds to OSI Physical and Data Link layer. • Physical layer • turning the data frame into a stream of bit. • manage and synchronizes the electrical of analog pulse. • Data Link layer • Media Access Control provides an interface with network adapter. • Logical Link Control performs error checking.

  10. Network Architecture • network architecture is referred to as a LAN type or a LAN topology such as ethernet. • network architecture is a design for the physical network and a collection of specifications defining communications dependent on the physical details.

  11. Specifications such as the following • Access method (set of rules defining how the computers will share the transmission medium) • Data frame format (enclosed in the header necessary to deliver data on the physical network) • Cabling type • Cabling rules (maximum and minimum lengths for the cable)

  12. Physical Addressing • The physical address is burned into the card at the factory. • Data frames sent across the LAN must use this physical address to identify the source and destination adapters. • TCP/IP uses the Address Resolution Protocol (ARP) and Reverse Address Resolution Protocol (RARP) to relate IP addresses to the physical addresses

  13. Anatomy of a Frame • The Network Access layer software accepts a datagram from the Internet layer and converts that data to a form that is consistent with the specifications of the physical network

  14. Network Access layer performs the following: • Breaks IP layer data into smaller chunks • Packages the chunks of data into frames • Passes the data frame to lower-level components corresponding to OSI's physical layer

  15. Example of ethernet frame • Preamble • Recipient address • Source address • Length • Data • Frame Check Sequence

  16. LAN Technologies • Ethernet • Token ring • FDDI

  17. Ethernet • Ethernet and Fast Ethernet are the LAN technologies most commonly used today. • Ethernet cable is inexpensive and easily installed. • Ethernet uses CSMA/CD.

  18. Technology Name Media Type Operating Speed Maximum Distance 10BASE-2 Thin coax 10 megabits 185 meters 10BASE-5 Thick coax 10 megabits 500 meters 10BASE-T CAT3 or CAT5 UTP 10 megabits 100 meters 10BASE-F Fiber optic 10 megabits 2,000 meters 100BASE-TX CAT 5 UTP or STP 100 megabits 100 meters 100BASE-FX Fiber optic 100 megabits 2,000 meters

  19. Token Ring • This method is known as token passing. • Computers on the LAN are connected so that data is passed around the network in a logical ring. • Central hub called a MAU or MSAU

  20. FDDI • Fiber Distributed Data Interface (FDDI) is an expensive • Employs a pair of fiber-optic rings. • One ring is considered primary and the second ring is there to replace the primary ring in the event of a breakdown.

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