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Understand Computer Networks II:

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Transcript

  • 1. Understanding Networks II
  • 2. Objectives
    • Compare client and network operating systems
    • Learn about local area network technologies, including Ethernet, Token Ring, FDDI, and wireless
    • Use the OSI model to understand networking
    • Learn how network computers and servers are addressed
  • 3. Network Architecture Overview
    • Network architecture is the overall design of a network, including how devices and components are connected, how devices and components communicate, and the network protocols needed to establish reliable communication among nodes on the network.
  • 4. Network Architecture Overview
    • A node is any device that can be accessed by a computer on a LAN, such as a computer, server, or printer.
    • Physical topology is the physical arrangement or shape in which devices on a LAN are connected to each other.
  • 5. How NICs Work
    • Typically, an internal NIC plugs into a motherboard expansion slot.
    • An individual NIC can be designed to support Ethernet, Token Ring, FDDI, or wireless architectures, but a single card will not support multiple architectures.
    • The NIC must convert the data it is transmitting into a signal that is in a form that is appropriate for the network.
    • The component on the card responsible for this signal conversion is called the transceiver .
  • 6. How Ethernet Controls Data Traffic
    • An Ethernet network is a passive network, meaning that the network just sits there and waits for a computer to use it.
    • A computer that wants to send packets over Ethernet first listens on the network for silence.
    • If it hears nothing, it begins to transmit.
    • As it transmits, it also listens.
  • 7. How Ethernet Controls Data Traffic (Continued)
    • If it hears something other than its own data being transmitted, it stops transmitting and sends out a signal indicating that there has been a collision, which occurs when two computers attempt to send data at the same time.
    • A collision can cause packets that were just sent to be corrupted.
    • Each computer waits for a random amount of time and then tries to transmit again, first listening for silence.
  • 8. How Ethernet Controls Data Traffic (Continued)
    • This type of network technology is called a contention-based system because each computer must contend for an opportunity to transmit on the network.
    • Computers using Ethernet gain access to the network using the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) method.
    • Another method that can be used by a network technology to control collisions is CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) .
  • 9. Ethernet Hardware
    • Three variations of Ethernet are available, primarily distinguished from one another by speed: 10-Mbps Ethernet, Fast Ethernet, and Gigabit Ethernet.
    • A hub is a network device that can be used to connect devices that use a BNC or RJ-45 connector.
    • A hub, like the one shown in Figure 5-20, is generally inexpensive and is best suited for a small, simple network.
    • These devices can include computers, servers, or printers.
  • 10. Ethernet Hardware (Continued)
    • Hubs are easy to configure because they broadcast data packets to every device at once.
    • A switch is used to connect computers on a LAN.
    • A switch reads the destination address at the beginning of a data packet and sends the packet only to the destination computer.
    • Attenuation occurs when signals are weakened due to being transmitted over long distances on a network.
  • 11. Ethernet Hardware (Continued)
    • A repeater is a device that amplifies signals on a network.
    • There are two kinds of repeaters.
    • An amplifier repeater simply amplifies all incoming signals.
    • A signal-regenerating repeater reads the signal and then creates an exact duplicate of the original signal before sending it on.
  • 12. Physical Topology
    • A bus topology connects each node in a line and does not include a centralized point of connection; cables just stretch from one computer to the next one, and to the next, and so on.
    • A star topology connects all nodes to a centralized hub or switch.
  • 13. Physical Topology (Continued)
  • 14. Wireless LAN
    • Wireless LAN (WLAN) technology, as the name implies, uses radio waves or infrared light instead of cables or wires to connect computers or other devices.
    • Connections are made using a wireless NIC, which includes an antenna to send and receive signals.
    • Wireless devices can communicate directly, or they can connect to a LAN by way of a wireless access point (AP) .
  • 15. Wireless LAN (Continued)
    • Access points are placed so that nodes can access at least on one access point from anywhere in the covered area.
    • The first IEEE standard that outlined wireless LAN specifications was IEEE 802.11, published in 1990.
    • Most current WLAN devices operate under the 1999 IEEE 802.11b standard.
    • This standard is also called Wi-Fi (Wireless Fidelity) .
  • 16. Token Ring and FDDI
    • Token Ring is an older LAN technology developed by IBM that transmits data at 4 Mbps or 16 Mbps.
    • A Token Ring network is physically arranged using a star topology, because each node connects to a centralized device.
    • The centralized device to which the network nodes connect is not a hub or switch, as used in Ethernet networks, but is called a Controlled Access Unit (CAU), a Multistation Access Unit ( MSAU or sometimes just MAU), or a Smart Multistation Access Unit (SMAU) .
  • 17. Token Ring and FDDI (Continued)
    • A token is a special series of bits used to control which device transmits data on the network.
    • Because it has a physical star topology and a logical ring topology, a Token Ring network is sometimes said to have a star-wired ring topology .
    • Token Ring can also use another type of connector that has no “male” or “female” version, known as a Universal Data Connector (UDC) or an IBM Data Connector (IDC).
  • 18. Token Ring and FDDI (Continued)
    • Fiber Distributed Data Interface (FDDI) is a type of network that also involves a token that travels in a ring.
    • With FDDI, data frames travel on the ring without the token, and multiple nodes can have data on the ring at the same time.

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