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Types of Communication Links

Types of Communication Links. Modem dial-up Leased Line ISDN Broadband ADSL cable broadband Ethernet broadband. Modem Dial up run-on telephone system no connection until dial-up OK a circuit-switched facility not packet-switched technology

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Types of Communication Links

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  1. Types of Communication Links • Modem dial-up • Leased Line • ISDN • Broadband • ADSL • cable broadband • Ethernet broadband

  2. Modem Dial up • run-on telephone system • no connection until dial-up OK • a circuit-switched facility • not packet-switched technology • = connection between 2 end-points in the network is occupied once it is connected • when the connection is over, the line is freed up for the other call

  3. Modem Dial-up (Cont’d) • a normal computer cannot perform connection to and signal transmission through telephone system • Computer uses digital signal • with only 0 / 1 …….. Either OFF or ON • no in-between states • Telephone line can transmit only analogue pulses • signal constantly varies in amplitude and frequency

  4. Digital Signal

  5. Analogue Signal

  6. Modem dial-up (cont’d) • In order for the successful transmission of signal • MODEM is required • MODEM = modulator demodulator • Convert Digital Signal to analogue signal and vice versa ? ?

  7. Modem dial-up (cont’d) • dial up connection • dedicated to the duration of the communication session • no other dial up connection is allowed until that dial up connection is finished • Circuit-switched facility / Circuit-switching • connection between two end points is occupied once connected

  8. Leased Lines • a telephone line that has been leased for private use • also circuit-switched facility • adv : • has guaranteed bandwidth • simplify planning • Disadv : • billing is fixed regardless how much bandwidth is used • no capacity to growth

  9. ISDN (Integrated Services Digital Network) • integrate both analogue data and digital data over the same network (upgrade switches of ISP) • can use the telephone system during data transmission • Two types of services (by ISP) • BRI (Basic Rate Interface) • for home use and small enterprise • PRI (Primary Rate Interface) • for large corporation

  10. ISDN (Cont’d) • BRI • consists of • 2 x 64 Kbps B-channels • 1 channel for 1 job • 1 x 16 Kbps D-channel • carrying control and signalling information • Total bandwidth (2B + D) = • 2 x 64 + 1 x 16 = 144 Kbps

  11. ISDN (Cont’d) • PRI (in USA) • consists of • 23 x 64 Kbps B-channels • 1 channel for 1 job • 1 x 64 Kbps D-channel • carrying control and signalling information • Total bandwidth (23B + D) = • 23 x 64 + 1 x 64 + ??? = 1.544 Mbps

  12. ISDN (Cont’d) • PRI (in Europe) • consists of • 30 x 64 Kbps B-channels • 1 channel for 1 job • 1 x 64 Kbps D-channel • carrying control and signalling information • Total bandwidth (30B + D) = • 30 x 64 + 1 x 64 + ??? = 2.048 Mbps

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