BRIDGES by lanyuehua

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									BRIDGES



     SIVA SAGAR TELLA
             INTRODUCTION
   Data communication device.
   Connects two or more LANs or segments of a
    single LAN.
   Operated at the Data Link Layer.
   Transparent to upper layer protocols.
DIFFERENCE BETWEEN BRIDGE & SWITCH

   BRIDGE – Maximum of 2-4 interfaces are present.
          - Connected between LANs or LAN
            segments.
   SWITCH – More number of interfaces are present.
           - Mostly used to connect to Computers
           TYPES OF BRIDGES
   LOCAL BRIDGES
      - provide a direct connection between
        multiple LAN segments in the same area.
   REMOTE BRIDGES
      - connect multiple LAN segments in different
        areas, usually over telecommunications
        lines.
BRIDGE BETWEEN DIFFERENT
          LANS
      FUNCTIONS OF BRIDGES

   LEARNING.
   FILTERING & FORWARDING.
                      LEARNING
   Records the MAC source address and the port on which
    the frame is received.
   Learned addresses are stored in an address table
    associated with each port (interface).
   Bridge implements an interface table using a software
    data structure or a Contents Addressable Memory (CAM)
    chip.
   Use the entries in the address tables later for forwarding
    the frames.
     FILTERING & FORWARDING
   When frame arrives, the destination address in the
    frame header is checked.
   Frame is discarded if the address is found in an interface
    table and the address is associated with the port on
    which frame is received.
   Frame is forwarded to the port which is associated with
    the address, if the address is not associated with the
    port on which the frame is received.
TABLES USED
               FILTER TABLE
   Contains a list of source addresses and
    destination addresses.
   Frames which match entries in the filter table
    will only be forwarded to specific configured
    ports.
   System administrator can control the data
    forwarding between different computers on the
    network.
               ADVANTAGES
   Flexibility in increasing the workstations on the
    LANs connected to the bridge.
   Transparent to the higher level protocols.
   Subdividing the LAN into smaller segments,
    increases overall reliability, and makes the
    network easier to maintain
                DRAWBACKS
   Network delay is introduced due to the overflow
    of buffer size for the address table.
    Limited number of ports unlike switches.
   Delay due to the modification of the protocols
    when connected between different LAN
    standards.
THANK YOU

								
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