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Homework

Homework. Chapter 14: HW 22, 24, 27, 28, 29, 31, 34,36,45,58, 59 a, b, c. Chapter 14 Switching. Circuit Switching Packet Switching Virtual circuit packet switching Datagram packet switching Message Switching. Switch.

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Homework

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  1. Homework • Chapter 14: • HW 22, 24, 27, 28, 29, 31, 34,36,45,58, 59 a, b, c

  2. Chapter 14Switching • Circuit Switching • Packet Switching • Virtual circuit packet switching • Datagram packet switching • Message Switching

  3. Switch • A hardware/software device capable of providing temporary connection among devices linked to the switch.

  4. Circuit switch may have n inputs and m outputs

  5. Switched Network

  6. VC approach Datagram approach Switched VC Permanent VC

  7. Circuit-Switched Network For mesh connection: No. of connections= n/2(n-1)=21 For point-to-point connection: No. of connections= n*m=12 Four switches are used to connect computers on the left to Computers on the right

  8. CircuitSwitching Networks • Dedicated circuit must be established first. • Data is transferred. • Data is transferred in bit streams. • Circuit is terminated • Example: (Public Switched Telephone Network, PSTN)

  9. CircuitSwitching Networks • Suitable for voice transmission. • Two devices must have the same data transmission rate. • Inflexible (once circuit is established, all data must follow the same path regardless of network conditions) • Not suitable for bursty traffic. • Circuits can be blocked. • You are charged for the circuit time. • The use of bandwidth may not be efficient.

  10. CircuitSwitching Technologies • Space-divisions switching • Crossbar switches • Multistage switches • Time-divisions switching

  11. Crossbar Switch

  12. Advantages of Crossbar Switch • Calls can not be blocked • Connection is instantaneous • Suitable for small number of inputs/outputs.

  13. Disadvantages of Crossbar Switch • The number of cross-points increases by approximately the square of the input/output devices. • Impractical for large number of inputs/outputs. • Inefficient use of the available circuits

  14. Multistage Switch 1 1 2 5 6 10 11 15 No. of crosspoints=3x(5x2)2*2x(3x3)+3x(2x5)=78 Single stage 15x15=225

  15. Disadvantage of Multistage Switch • Blocking

  16. Switching Path

  17. Switching Path

  18. Time-Division Switches • TDM is used to achieve switching. • Two TDM methods used are: • Time-slot interchange • TDM bus • Synchronous • Asynchronous

  19. TDM without Time-Slot Interchange (TSI)

  20. TDM with TSI

  21. Time-Slot Interchange (TSI)

  22. Advantage and Disadvantage of Time-Division Switching • Advantage: • It does not need crosspoints. • Disadvantages: • Processing time (data must be stored in RAM, retrieved, and processed)

  23. TDM Bus • I/O lines connected to high speed bus through I/O gates. • I/O lines are assigned time slot. • Devices can transmit during their assigned time slot. • One input gate is closed and only one output gate is closed during each time slot.

  24. Circuit Switching • Total transmission time • Call setup time • Signal propagation time • Data transmission time • ttot=ts+t prop.+ttrans.

  25. Circuit Switching (example) • The speed of propagation on a TDM bus is 0.8c, its length is 1 m, and the data rate is 500 Mbps. Calculate the total time to transmit 10 Mbytes of data. • ttot=ts+t prop.+ttrans.

  26. Circuit Switching Networks (review) • Suitable for voice transmission. • Two devices must have the same data transmission rate.(constant rate) • Not suitable for bursty traffic. • Inflexible (once circuit is established, all data must follow the same path regardless of network conditions) • Circuits can be blocked. • You are charged for the circuit time. • The use of bandwidth may not be efficient.

  27. Packet Switching Datagram approach VC approach Switched VC Permanent VC

  28. Packet Switching Networks • Suitable for audio, video, data transmission. • Two devices with different transmission speeds can exchange data. (variable data rate) • Priorities can be assigned. • Suitable for bursty traffic. • Circuits can not be blocked.

  29. Switched Virtual Circuit

  30. Switched Virtual Circuit

  31. Switched Virtual Circuit

  32. Virtual Circuit Packet SwitchingNetworks • Total transmission time • Call setup time for VC • Signal propagation time • Packets transmission time • ttot=ts+t prop.+ttrans.

  33. Datagram Approach

  34. Datagram Packet SwitchingNetworks • Total transmission time • Signal propagation time • Packets transmission time • ttot=t prop.+ttrans.

  35. Datagram Approach, Multiple Channels

  36. Message Switching

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