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Figure 6.19 illustrates the use of the bridge in a network. Suppose node A on LAN segment 1 wishes to send a packet
        to node G on segment 3. On receiving this packet from node A, the bridge will examine its destination address and
        forward it only to LAN segment 3.








                              A           B                                            LAN
                                                                                       Segment 2

                     LAN
                   Segment 1                           BRIDGE
                                                                        G                I
                                    C                                                       LAN
                                                                                            Segment 3


                                                                             H
                                                     Figure 6.19 Bridge

        6.5.6 Switch

        Like hubs, switches also connect individual computers. Each computer is connected to a unique port on a switch.
        However, it does not transmit an incoming frame to all the computers attached to it. When a switch receives a frame
        from a LAN segment, it examines the incoming frame’s destination address and forwards it to the appropriate node.
        However, on receiving a corrupted packet, the switch asks the sender to transmit it again. A store and forward switch
        would wait until it receives a complete frame and then transmits it to the destination. Alternatively, a cut-through
        switch  initiates the process of forwarding the data as soon as it receives the frame’s destination address. Figure 6.20
        shows the use of a switch in a network. If node A wishes to send a message to node G, it will pass the message to the
        switch, which will transmit it on the line that connects to node G.

                          A                                                                  L
                          B                                                                  K
                          C                                                                  J


                                                 D    E   F   G    H   I
                                                     Figure 6.20 Switch

        6.5.7 Modem

        Whereas computers store and process data digitally, traditional telephone lines deal with analog signals. A modem
        connects a computer to the Internet using telephone lines. It combines the modulation and demodulation functions
        by transforming a digital signal to an analog signal and vice-versa. Digital data to be sent from a computer is modulated
        for transmission over telephone lines. Similarly, at the receiving end, analog data is demodulated to digital form. A
        modem’s speed is expressed in  bits per second or in terms of baud rate.

        A modem may be placed internally in an expansion slot of a computer, or it may be connected externally to a port.
        Nowadays, wireless modems are also in use that do not require a physical connection with a computer. Figure 6.21
        explains the use of modems in a network. Suppose node A wishes to send data to node B, digital data sent by node A
        passes through the modem, which converts it into an analog signal. The analog signal generated is transmitted via the
        telephone network. At the other end, a modem converts the signal back into digital form, which is sent to node B. A
        modem also compresses the data before sending and uncompresses it at the receiving end.

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