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# Multiplexing and switching(TDM ,FDM, Data gram, circuit switching)

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its include switching(data gram , circuit switching etc) and multiplexing and multiplexing (FDM AND TDM)

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### Multiplexing and switching(TDM ,FDM, Data gram, circuit switching)

1. 1. Multiplexing and Switching
2. 2. Multiplexing Sharing the link among multiple users
3. 3. Multiplexing Time Division Multiplexing (TDM)  Synchronous TDM  Statistical TDM Frequency Division Multiplexing (FDM)
4. 4. Time Division Multiplexing The Basic Idea:  As the name suggest, Divide time amongst the users  Give each user some time to transmit his data  This process is periodic in a round robin fashion  The time given to a each user is referred to as Time Slot or Time Quantum
5. 5. Time Division Multiplexing
6. 6. MUX 12 1 3 23 123 THE TRANSMITTER
7. 7. 12 13 23 123 THE LINK
9. 9. There should be no Timing difference between the MUX and DEMUX WARNING………!!!!!!!
10. 10. DEMUX Or else……..!!!! Something like this will happen……!!!!!
11. 11. Therefore, the two devices should be synchronized…… And so it is called Synchronous TDM
12. 12. The problem with Synchronous TDM What if host2 has only one packet to send and host3 has two packet to send…….. MUX 12 1 3 12
13. 13. 12 13 12 THE LINK
14. 14. Time slots are being wasted….!!
15. 15. The solution is Statistical TDM
16. 16. Statistical TDM Here Time slots are given on demand……….rather than in round robin fashion Each User can get 2 or more consecutive time slots If time slot is not required, it is not allocated Hence, not wasted
17. 17. Frequency Division Multiplexing
18. 18. Frequency Division Multiplexing Diagram
19. 19. FDM Sharing is done by assigning each user a specific frequency (Carrier Frequency) Modulation equipment is used to move each signal to the required frequency band. Multiplexing equipment is needed to combine the modulated signal
20. 20. User 1 User 2 User 3 M O D U L A T O R f1 f2 f3
21. 21. All the users transmit their data simultaneously…. f1 f2 f3
22. 22. The Received data at the Receiver f1 f2 f3 f1 f2 f3 The Filter The output f1 f2 f3
23. 23. fc y(f) Demodulate to get the original signal back
24. 24. Switching
25. 25. Switching Networks A network is made up of end hosts and intermediate switching nodes Data is usually passed through a network of intermediate switching nodes The Switching nodes: Not concerned with the contents of the data; • Provide a switching facility that will move data from node to node until they reach their destination
26. 26. A 1 7 2 5 3 4 6 B C D E F Switching Nodes End Hosts
27. 27. Some Notes…  Some nodes only connect to other nodes  Some nodes connect to end hosts also  Usually the network is not fully connected; there is not a direct link between each pair of nodes  If there are more than one paths between any pair of nodes; this increases the reliability of the network  Node-Node links are usually multiplexed
28. 28. Two Technologies for Switching Circuit Switching Packet Switching They differ in the way the nodes switch information from one link to another on the way from source to destination
29. 29. Circuit Switching A dedicated communication path between the hosts
30. 30. A 1 7 2 5 3 4 6 B C D E F Switching Nodes End Hosts
31. 31. Three Phases  Circuit Establishment • Host-B send a connection request towards Host-D • Intermediate nodes route the request to Host-D based on measures of availability and cost • If ready, D accepts the connection and a dedicated path (generally full duplex) is established from B through the intermediate nodes to D  Data Transfer • The data (analog/digital) is carried on the dedicated path  Circuit Disconnect • Done by any one station • Signals are propagated to intermediate nodes to de- allocate the dedicated resources
32. 32. Principles • Circuit switching designed for voice – Resources dedicated to a particular call – Much of the time a data connection is idle – Data rate is fixed • Both ends must operate at the same rate
33. 33. Packet Switching
34. 34. Problems in Circuit Switching  Circuit Switching approach is inefficient  Since data rate is constant, therefore the devices interconnected must transmit and receive at the same data rate, This limits the interconnection of variety of hosts  Further calls are blocked when all the lines are busy
35. 35. Packet Switching…...A quick overview  Data is transmitted in short packets  If a source has larger message to send, the message is broken up into a series of packets  Each packet contains user’s data plus some control information (header)  The control information, at a minimum includes the information that the network requires to be able to route the packet through the network and deliver it to the intended destination  At each node the packet is received, stored briefly and passed on to the next node
36. 36. Advantages  Line efficiency is greater  A packet switching network can perform data rate conversion  In Circuit Switching, calls are blocked whereas in P.S. packets are still accepted but delivery delay increases  Priorities can be used, thus a higher priority packet experiences less delay
37. 37. Types of Packet Switching Datagram Approach Virtual Circuit Approach
38. 38. Datagram Packet Switching  Each packet is treated independently, with no reference to packets that have gone before  Each packet contains the address of its destination  The packets with the same destination do not always follow the same route  Some packets can get late and some can get destroyed in the network  Therefore, packets can be received out of order at the destination  There must be some mechanism of re-ordering at the receiver  Each packet, treated independently, is referred to as datagram
39. 39. A B
40. 40. Virtual Circuit Packet Switching A preplanned route is established before any packets are sent All the packets follow that route Just like circuit switching, the route should be terminated after the transmission of data
41. 41. DisconnectData Connect Accept
42. 42. Packets will be received in order However, packets can get lost on the way
43. 43. Event Timing