Network Devices Repeaters, hubs, bridges, switches, routers ...


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Network Devices Repeaters, hubs, bridges, switches, routers ...

  1. 1. Network Devices Repeaters, hubs, bridges, switches, routers, NIC’s
  2. 2. Devices and the layers at which they operate Hubs Physical 1 Switches, bridges, NIC’s Data Link 2 Routers, layer 3 switches Network 3 Device Name of Layer Layer
  3. 3. NIC’s ( Network Interface Cards ) <ul><li>This NIC has interfaces for twisted pair, thicknet, and thinnet connectors. </li></ul>
  4. 4. Repeaters <ul><li>Signal attenuation or signal loss – signal degrades over distance </li></ul><ul><li>Repeaters clean, amplify, and resend signals that are weakened by long cable length. </li></ul><ul><li>Built-in to hubs or switches </li></ul>
  5. 5. Hubs <ul><li>OSI layer 1 hardware </li></ul><ul><li>Hubs regenerate and retime network signals </li></ul><ul><li>Hubs propagate signals through the network </li></ul><ul><li>They cannot filter network traffic </li></ul><ul><li>They cannot determine best path </li></ul><ul><li>They are used as network concentration points </li></ul><ul><li>They are really multi-port repeaters </li></ul><ul><li>Uplink port – crossover mode or straight through mode </li></ul>
  6. 6. Bridges <ul><li>A layer 2 device designed to create two or more LAN segments, each of which is a separate collision domain. </li></ul><ul><li>The purpose is to filter traffic on a LAN, to keep local traffic local, yet allow connectivity to other segments of the network. </li></ul><ul><li>Filter traffic by looking at the MAC address </li></ul><ul><li>Frame filtering </li></ul>
  7. 7. Bridges <ul><li>If the frame is addressed to a MAC address on the local side of the bridge, it is not forwarded to the other segment </li></ul><ul><li>MAC addresses on the other segment are forwarded </li></ul><ul><li>Bridges maintain a MAC address table for both segments they are connected to </li></ul>
  8. 8. Cycle of bridges <ul><li>Bridged network can span many segments </li></ul><ul><li>Broadcasts are sent to all segments </li></ul>
  9. 9. Bridges Distributed Spanning Tree <ul><li>If all bridges forward broadcasts, infinite loops can occur </li></ul><ul><li>Bridges perform DST on boot to determine which bridges will not forward broadcasts </li></ul>
  10. 10. Switched networks <ul><li>Shared ethernet networks perform best when kept to 30-40 percent full capacity </li></ul><ul><li>This is a result of CSMA/CD </li></ul><ul><li>A LAN switch is a high-speed multiport bridge which segments each port into its own collision domain and can access the full bandwidth </li></ul>
  11. 11. Devices and the layers at which they operate Hubs Physical 1 Switches, bridges, NIC’s Data Link 2 Routers, layer 3 switches Network 3 Device Name of Layer Layer
  12. 12. Switches <ul><li>Each port is a simulated segment to itself </li></ul>
  13. 13. Store and Forward Switches <ul><li>Do error checking on each frame after the entire frame has arrived into the switch </li></ul><ul><li>If the error checking algorithm determines there is no error, the switch looks in its MAC address table for the port to which to forward the destination device </li></ul><ul><li>Highly reliable because doesn’t forward bad frames </li></ul><ul><li>Slower than other types of switches because it holds on to each frame until it is completely received to check for errors before forwarding </li></ul>
  14. 14. Cut Through Switch <ul><li>Faster than store and forward because doesn’t perform error checking on frames </li></ul><ul><li>Reads address information for each frame as the frames enter the switch </li></ul><ul><li>After looking up the port of the destination device, frame is forwarded </li></ul><ul><li>Forwards bad frames </li></ul><ul><ul><li>Performance penalty because bad frames can’t be used and replacement frames must be sent which creates additional traffic </li></ul></ul>
  15. 15. Fragment free cut through switch <ul><li>Combines speed of cut through switch with error checking functionality </li></ul><ul><li>Forwards all frames initially, but determines that if a particular port is receiving too many bad frames, it reconfigures the port to store and forward mode </li></ul><ul><li>Preferred switching solution </li></ul>
  16. 16. Unmanaged/Intelligent switches <ul><li>Unmanaged – provides LAN’s with all the benefits of switching </li></ul><ul><li>Fine in small networks </li></ul><ul><li>Intelligent switches tracks and reports LAN performance statistics </li></ul><ul><li>Have a database ASIC (application specific integrated circuit) on board to collect and store data which you view through a software interface </li></ul>
  17. 17. Layer 3 switch <ul><li>By definition a switch filters or forwards frames based on MAC addresses. This makes a switch a layer 2 device. </li></ul><ul><li>Now we have layer 3 switches which have routing capability. If a data frame can’t be switched it is routed. </li></ul><ul><li>Each port is a separate LAN port, but the forwarding engine actually calculates and stores routes based on IP addresses, not MAC addresses </li></ul><ul><li>Usually support only IP or IP and IPX </li></ul>
  18. 18. VLAN Switches <ul><li>Virtual local area network </li></ul><ul><li>Each port on a switch defines a collision domain </li></ul><ul><li>The entire switch forms a single broadcast domain </li></ul><ul><li>VLANs can define multiple broadcast domains </li></ul><ul><li>Network traffic that is directed to all computers on the network can be segmented to transmit only on a specific VLAN. </li></ul><ul><li>Improves bandwidth on a the VLAN’s because each VLAN filters the network-to-network broadcast traffic as well as the collision traffic from other VLAN’s </li></ul>
  19. 19. Physical Layer Broadcast <ul><li>Physical layer broadcasts – implemented by non-switched Ethernet networks through shared cabling and hubs </li></ul><ul><ul><li>Each bit that is transmitted is physically received by every station </li></ul></ul><ul><ul><li>Switches and VLAN’s don’t do physical layer broadcasts </li></ul></ul>
  20. 20. MAC-level broadcast <ul><li>MAC-level broadcast – deal with how to handle MAC level broadcast frames; that is the data frames that have a broadcast destination MAC address </li></ul><ul><li>MAC-level broadcast frames are addressed to all MAC addresses on a given network (not a network segment, but an actual network as defined by its network address) </li></ul><ul><li>A regular switch forwards all broadcast frames out all ports, but a VLAN switch forwards broadcast frames only to ports that are part of the same VLAN </li></ul><ul><li>Multiple switches can be part of the same VLAN </li></ul>
  21. 21. VLAN Switches <ul><li>None of the VLAN’s can communicate unless each VLAN is connected to a router or layer 3 switch </li></ul><ul><li>Each VLAN is separating collision traffic associated with MAC Addresses (layer 2) and each VLAN is separating the network-to-network broadcast traffic. In other words each VLAN is acting as a separate network so a layer 3 device is necessary for them to communicate </li></ul>