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					      Network Technologies

1. Ethernet
2. Token Ring
3. FDDI




                             1
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method




                                                               2
Network Technologies

Ethernet                Token Ring                FDDI
•   Types               •   Types                 •    Types
•   Access Method       •   Access Method         •    Access Method




                                              10-Base 5


           •   The first number (10, 1, or 100)
               indicates the data rate in Mbps



                                  •   Base: specifies a digital signal
                                      Broad: specifies analog signal

                                            Only one specification for b
                                  roadband category 10 Borad 36


                                                                           •   The last number or letter (5, 2, 1, or T)
                                                                               indicates the maximum cable length or th
                                                                               e type of cable
                                                                                                               3
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method


                             10Base5: Thick Ethernet
Bus Topology




                             10Base2: Thin Ethernet
Bus Topology




                                                               1-4
Network Technologies

Ethernet               Token Ring                 FDDI
•   Types              •   Types                  •   Types
•   Access Method      •   Access Method          •   Access Method



                       10BaseT: Twisted-Pair Ethernet
Star Topology


                                           100m




                           10Base-F: Fiber Ethernet
Star Topology




                                                                      1-5
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method




                       Access Method CSMA/CD




                                                               1-6
Network Technologies

Ethernet                Token Ring                  FDDI
•   Types               •    Types                  •    Types
•   Access Method       •    Access Method          •    Access Method




                       Access Method                                   CSMA/CD
           Need for a Access Method

           • Whenever multiple users have unregulated access to a single line, there is a danger of signals overlapp
           ing and destroying each other

           • Such overlaps which turn signals to Noise are called COLLISIONS

           • As traffic increases on multiple-access link, so do collisions

           • A LAN therefore needs a mechanism to coordinate traffic, minimize the number of collisions and max
           imizes the number of frames that are delivered successfully

            • The access mechanism used in Ethernet is called Carrier Sense Multiple Access with Collision Det
           ection (CSMA/CD)


                                                                                                              1-7
Network Technologies

Ethernet               Token Ring           FDDI
•   Types              •   Types            •   Types
•   Access Method      •   Access Method    •   Access Method


                    Access Method                       CSMA/CD
                       MA  CSMA  CSMA/CD
          • Multiple Access (MA) :    Multiple users access to a single line
          • Carrier Sense (CS) :      A device listens to the line before it transmits
          • Collision Detection (CD): Extremely high voltage indicates a collision

          The station wishing to transmit:

                1. Listens to make certain the link is free (checking voltage in the line)
                2. Transmits its data
                3. Listens again (checking for High voltage in the line)

          If a collision is detected:

                1. The station quits the current TX
                2. Waits a predetermined amount of time for the line to clear
                3. Sends its data again
                                                                                             1-8
Network Technologies

Ethernet               Token Ring           FDDI
•   Types              •   Types            •   Types
•   Access Method      •   Access Method    •   Access Method




                                           Token Ring
          • Token ring allows each station to send one frame per turn

          • Token is a short message passing around the ring




                                                                    1-9
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method



                    Access Method: Token Passing
Ring Topology




                                                               1-10
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method


        •   Token is a short message passing around the ring (Token and data flow in
            one direction)

        •   Until a computer wishes to send data

        •   The sender computer holds the token and sends its own data including the
            sender and the receiver address

        •   Each computer retransmit what it receives from the previous computer.
            Active network (no loss or attenuation as in bus)

        •   Until the electronic address matches the receiving computer

        •   The receiving computer sends a message to the sender computer indicatin
            g that receives the data.

        •   The sender computer creates and send Token and places it on the network

                                                                                       1-11
Network Technologies

Ethernet               Token Ring          FDDI
•   Types              •   Types           •   Types
•   Access Method      •   Access Method   •   Access Method




        •   FDDI Fiber Distributed Data Interface

        •   CDDI copper version of the FDDI




        •   Access method is Token Ring




                                                               1-12

				
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posted:11/26/2012
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