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Chapter 8 Circuit Switching & Telephone Network

Chapter 8 Circuit Switching & Telephone Network. Circuit switching Telephone network. Switching. Whenever we have multiple devices, we have the problem of how to connect them to make one-one-one communication possible. Circuit-switched Network.

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Chapter 8 Circuit Switching & Telephone Network

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  1. Chapter 8Circuit Switching & Telephone Network Circuit switching Telephone network Data Communications, Kwangwoon University

  2. Switching Whenever we have multiple devices, we have the problem of how to connect them to make one-one-one communication possible. Data Communications, Kwangwoon University

  3. Circuit-switched Network • Creates a direct physical connection between two devices such as phones or computer Data Communications, Kwangwoon University

  4. A Circuit Switch • Device with n inputs and m outputs that creates a temporary connection between an input link and output link Data Communications, Kwangwoon University

  5. A Folded Switch • n-by-n folded switch can connect n lines in full-duplex mode Data Communications, Kwangwoon University

  6. Circuit Switching Technologies Data Communications, Kwangwoon University

  7. Crossbar Switch Data Communications, Kwangwoon University

  8. Crossbar Switches: Problem • The number of switches is huge. • connect n inputs by m output -- require n * m crosspoint. • Ex : 1000 input, 1000 output → 1,000,000 crosspoint • Inefficient • fewer than 25% of the crosspoints are in use at a given time. Data Communications, Kwangwoon University

  9. Multistage Switch Data Communications, Kwangwoon University

  10. Switching Path Data Communications, Kwangwoon University

  11. Multistage Switches: Advantage • Advantage: The number of crosspoints • single-stage switch ~ need 225 crosspoint(15 * 15) • multistage switch ~ first-stage : 10 crosspoint(5 * 2) *3 = 30 crosspoint ~ second-stage : 9 crosspoint(3 *3) * 2 = 18 crosspoint ~ third-stage : 10 crosspoint(5 * 2) *3 = 30 crosspoint total number of crosspoint : 78 • Disadvantage: Call blocking Data Communications, Kwangwoon University

  12. TDM, with and without TSI Data Communications, Kwangwoon University

  13. Time-Slot Interchange Data Communications, Kwangwoon University

  14. TDM Bus Data Communications, Kwangwoon University

  15. Combinations • Space Division SW : Simple (O), Crosspoints (X) • Time Division SW : Processing delay (X) • Space-and Time-Division Switching combinations take advantage of the best of both • TST(time-space-time) • TSST(time-space-space-time) • STTS(space-time-time-space) Data Communications, Kwangwoon University

  16. TST Switch Data Communications, Kwangwoon University

  17. A Telephone System Data Communications, Kwangwoon University

  18. Telephone Companies: Brief History • Before 1984 • Almost all services are provided by AT&T Bell System • In 1984, AT&T was broken into • AT&T long Lines • 23 BOCs(Bell Operating Companies) • BOCs are grouped together to several RBOCs • Between 1984 and 1996 • Divided into more than 200 LATAs (Local Access Transport Areas) • After 1996 • Any companies can provide any services Data Communications, Kwangwoon University

  19. LATAs • A LATA can be a small or large metropolitan area • Intra-LATA services are provided by local exchange carriers • ILEC (Incumbent Local Exchange Carriers) • CLEC (Competitive Local Exchange Carriers) • Inter-LATA services are handled by IXCs (Inter-Exchange Carriers) • Called long-diatance companies Data Communications, Kwangwoon University

  20. Switching Offices in a LATA Data Communications, Kwangwoon University

  21. POP (Point of Presence) Data Communications, Kwangwoon University

  22. Rotary and Touch-Tone Dialing Data Communications, Kwangwoon University

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