Understand Computer Networks II:


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Understand Computer Networks II:

  1. 1. Understanding Networks II
  2. 2. Objectives <ul><li>Compare client and network operating systems </li></ul><ul><li>Learn about local area network technologies, including Ethernet, Token Ring, FDDI, and wireless </li></ul><ul><li>Use the OSI model to understand networking </li></ul><ul><li>Learn how network computers and servers are addressed </li></ul>
  3. 3. Network Architecture Overview <ul><li>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. </li></ul>
  4. 4. Network Architecture Overview <ul><li>A node is any device that can be accessed by a computer on a LAN, such as a computer, server, or printer. </li></ul><ul><li>Physical topology is the physical arrangement or shape in which devices on a LAN are connected to each other. </li></ul>
  5. 5. How NICs Work <ul><li>Typically, an internal NIC plugs into a motherboard expansion slot. </li></ul><ul><li>An individual NIC can be designed to support Ethernet, Token Ring, FDDI, or wireless architectures, but a single card will not support multiple architectures. </li></ul><ul><li>The NIC must convert the data it is transmitting into a signal that is in a form that is appropriate for the network. </li></ul><ul><li>The component on the card responsible for this signal conversion is called the transceiver . </li></ul>
  6. 6. How Ethernet Controls Data Traffic <ul><li>An Ethernet network is a passive network, meaning that the network just sits there and waits for a computer to use it. </li></ul><ul><li>A computer that wants to send packets over Ethernet first listens on the network for silence. </li></ul><ul><li>If it hears nothing, it begins to transmit. </li></ul><ul><li>As it transmits, it also listens. </li></ul>
  7. 7. How Ethernet Controls Data Traffic (Continued) <ul><li>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. </li></ul><ul><li>A collision can cause packets that were just sent to be corrupted. </li></ul><ul><li>Each computer waits for a random amount of time and then tries to transmit again, first listening for silence. </li></ul>
  8. 8. How Ethernet Controls Data Traffic (Continued) <ul><li>This type of network technology is called a contention-based system because each computer must contend for an opportunity to transmit on the network. </li></ul><ul><li>Computers using Ethernet gain access to the network using the CSMA/CD (Carrier Sense Multiple Access with Collision Detection) method. </li></ul><ul><li>Another method that can be used by a network technology to control collisions is CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) . </li></ul>
  9. 9. Ethernet Hardware <ul><li>Three variations of Ethernet are available, primarily distinguished from one another by speed: 10-Mbps Ethernet, Fast Ethernet, and Gigabit Ethernet. </li></ul><ul><li>A hub is a network device that can be used to connect devices that use a BNC or RJ-45 connector. </li></ul><ul><li>A hub, like the one shown in Figure 5-20, is generally inexpensive and is best suited for a small, simple network. </li></ul><ul><li>These devices can include computers, servers, or printers. </li></ul>
  10. 10. Ethernet Hardware (Continued) <ul><li>Hubs are easy to configure because they broadcast data packets to every device at once. </li></ul><ul><li>A switch is used to connect computers on a LAN. </li></ul><ul><li>A switch reads the destination address at the beginning of a data packet and sends the packet only to the destination computer. </li></ul><ul><li>Attenuation occurs when signals are weakened due to being transmitted over long distances on a network. </li></ul>
  11. 11. Ethernet Hardware (Continued) <ul><li>A repeater is a device that amplifies signals on a network. </li></ul><ul><li>There are two kinds of repeaters. </li></ul><ul><li>An amplifier repeater simply amplifies all incoming signals. </li></ul><ul><li>A signal-regenerating repeater reads the signal and then creates an exact duplicate of the original signal before sending it on. </li></ul>
  12. 12. Physical Topology <ul><li>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. </li></ul><ul><li>A star topology connects all nodes to a centralized hub or switch. </li></ul>
  13. 13. Physical Topology (Continued)
  14. 14. Wireless LAN <ul><li>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. </li></ul><ul><li>Connections are made using a wireless NIC, which includes an antenna to send and receive signals. </li></ul><ul><li>Wireless devices can communicate directly, or they can connect to a LAN by way of a wireless access point (AP) . </li></ul>
  15. 15. Wireless LAN (Continued) <ul><li>Access points are placed so that nodes can access at least on one access point from anywhere in the covered area. </li></ul><ul><li>The first IEEE standard that outlined wireless LAN specifications was IEEE 802.11, published in 1990. </li></ul><ul><li>Most current WLAN devices operate under the 1999 IEEE 802.11b standard. </li></ul><ul><li>This standard is also called Wi-Fi (Wireless Fidelity) . </li></ul>
  16. 16. Token Ring and FDDI <ul><li>Token Ring is an older LAN technology developed by IBM that transmits data at 4 Mbps or 16 Mbps. </li></ul><ul><li>A Token Ring network is physically arranged using a star topology, because each node connects to a centralized device. </li></ul><ul><li>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) . </li></ul>
  17. 17. Token Ring and FDDI (Continued) <ul><li>A token is a special series of bits used to control which device transmits data on the network. </li></ul><ul><li>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 . </li></ul><ul><li>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). </li></ul>
  18. 18. Token Ring and FDDI (Continued) <ul><li>Fiber Distributed Data Interface (FDDI) is a type of network that also involves a token that travels in a ring. </li></ul><ul><li>With FDDI, data frames travel on the ring without the token, and multiple nodes can have data on the ring at the same time. </li></ul>