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COMPUTER NETWORKS

COMPUTER NETWORKS. Mr. DEEPAK P. Associate Professor ECE Department SNGCE. UNIT 4. Asynchronous Transfer Mode (ATM). DEEPAK.P. 3. ATM (Asynchronous Transfer Mode). Asynchronous Transfer Mode (ATM) is a new network technology designed for “integrated services”

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COMPUTER NETWORKS

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  1. COMPUTER NETWORKS Mr. DEEPAK P. Associate Professor ECE Department SNGCE DEEPAK.P

  2. UNIT 4 DEEPAK.P

  3. Asynchronous Transfer Mode (ATM) DEEPAK.P 3

  4. ATM (Asynchronous Transfer Mode) Asynchronous Transfer Mode (ATM) is a new network technology designed for “integrated services” “ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (guaranteed capacity and constant transmission delay) with those of packet switching (flexibility and efficiency for intermittent traffic)” ATM standard (defined by CCITT) is widely accepted by common carriers as mode of operation for communication. Consultative Committee for International Telephony & Telegraphy ATM is a form of cell switching using small fixed-sized packets. DEEPAK.P 4

  5. ATM (Asynchronous Transfer Mode) DEEPAK.P 5

  6. ATM (Asynchronous Transfer Mode) It can carry a variety of different types of traffic, such as Voice Video Data DEEPAK.P 6

  7. ATM (Asynchronous Transfer Mode) Switching will be done on cells. ATM is asynchronous transmission. In ATM, each cell is independently transmitted. In ATM the fixed size packets are referred to as Cells. ATM will be connection-oriented. Vast majority of ATM networks will run on optical fiber networks with extremely low error rates. DEEPAK.P 7

  8. Working of ATM DEEPAK.P 8

  9. Working of ATM ATM is connection-oriented -- an end-to-end connection must be established and routing tables setup prior to cell transmission Once a connection is established, the ATM network will provide end-to-end Quality of Service (QoS) to the end users All traffic, whether voice, video, image, or data is divided into 53-octet cells and routed in sequence across the ATM network DEEPAK.P 9

  10. Working of ATM Routing information is carried in the header of each cell Routing decisions and switching are performed by hardware in ATM switches Cells are reassembled into voice, video, image, or data at the destination DEEPAK.P 10

  11. ATM Network Public ATM Network: Provided by public telecommunications carriers (e.g., AT&T, MCI WorldCom, and Sprint) Interconnects private ATM networks Interconnects remote non-ATM LANs Interconnects individual users DEEPAK.P 11

  12. ATM Network Private ATM Network: Owned by private organizations Interconnects low speed/shared medium LANs (e.g., Ethernet, Token Ring, FDDI) as a backbone network Interconnects individual users as the front-end LAN for high performance or multimedia applications DEEPAK.P 12

  13. ATM Architecture DEEPAK.P 13

  14. ATM Architecture DEEPAK.P 14

  15. ATM Architecture DEEPAK.P 15

  16. ATM Architecture DEEPAK.P 16

  17. ATM Devices ATM networks are built around two categories of devices ATM Switch ATM end-point Interfaces An ATM switch can be connected to either another ATM switch or and ATM end-point. Interfaces are two types NNI---Network-Network-Interface UNI---User Network Interface DEEPAK.P 17

  18. ATM Interfaces ATM switch supports two types of interfaces User-Network Interface (UNI) Connects an ATM end-point to a switch Network-Network Interface (NNI) Connects two ATM switches UNI and NNI can further be divided to two types One is known as the private type and the other is known as the public type DEEPAK.P 18

  19. ATM Interfaces DEEPAK.P 19

  20. ATM Interfaces Private UNI Connects an ATM end-point to a private ATM switch Public UNI Connects an ATM end-point or a private ATM switch to a public ATM switch Private NNI Connects two ATM switches within the same private organization Public NNI Connects two ATM switches within the same public organization DEEPAK.P 20

  21. Statistical multiplexing in ATM DEEPAK.P 21

  22. ATM Services DEEPAK.P 22

  23. ATM Services There are basically three types of ATM services Permanent Virtual Circuits (PVC) Switched Virtual Circuits (SVC) Connectionless Service PVC allows direct connectivity between sites. PVC guarantees availability of a connection and does not require call setup procedures between switches Each piece of equipment between the source and the destination must be manually provisioned for the PVC DEEPAK.P 23

  24. ATM Services SVC is the most widely used service An SVC is created and released dynamically and remains in use only as long as data is being transferred The advantages of SVCs include connection flexibility and call setup that can be handled automatically by a networking device. DEEPAK.P 24

  25. ATM Services Two types of ATM connections exist: Virtual paths, which are identified by virtual path identifiers, and Virtual channels, which are identified by the combination of a VPI and a virtual channel identifier (VCI). A virtual path is a bundle of virtual channels, all of which are switched transparently across the ATM network based on the common VPI A transmission path is the physical media that transports virtual channels and virtual paths. DEEPAK.P 25

  26. ATM Services DEEPAK.P 26

  27. Virtual Path and Virtual Channels Virtual Channels (VC) ATM Physical LinkVirtual Channel Connection (VCC) Virtual Path (VP) Virtual Path (VP) Virtual Channels (VC) Virtual Channel(VC)Logical PathBetween ATM End Points Virtual Channel Connection(VCC)Contains Multiple VPs Virtual Path(VP)Contains Multiple VCs Connection Identifier = VPI/VCI DEEPAK.P 27

  28. ATM Services The cell is received across a link on a known VCI or VPI value. The switch looks up the connection value in a local translation table to determine the outgoing port (or ports) of the connection and the new VPI/VCI value of the connection on that link. DEEPAK.P 28

  29. Connections Vs Channels DEEPAK.P 29

  30. VP/VC Assignment DEEPAK.P 30

  31. VP/VC Switching DEEPAK.P 31

  32. VP/VC Switching DEEPAK.P 32

  33. Hierarchy of function in an ATM DEEPAK.P 33

  34. Hierarchy of function in an ATM-based network. ATM network will be organized as a hierarchy. DEEPAK.P 34

  35. ATM Protocol Architecture DEEPAK.P 35

  36. ATM-protocol architecture • 2 primary protocol layers relate to ATM functions: • Common layer providing packet transfers, logical connections (ATM) • Service dependent ATM adaptation layer (AAL) • Protocol Model has 3 planes • User • Control • Management DEEPAK.P 36

  37. ATM Protocol Architecture DEEPAK.P 37

  38. ATM-protocol architecture User – provides for user information transfer and associated controls (flow control, congestion control) Control– performs call control and connection control functions (signaling) Management – provides plane management and layer management and coordination functions DEEPAK.P 38

  39. ATM layers DEEPAK.P 39

  40. Functions of Layers Convergence AAL Segmentation and Reassembly Generic Flow Control Cell VPI/VCI translation Cell multiplexing and demultiplexing Cell header generation and extraction ATM HEC header sequence generation and verification Cell delineation Transmission frame generation and recovery TC Physical Bit timing Physical medium PM DEEPAK.P 40

  41. ATM Protocol Layers DEEPAK.P 41

  42. ATM-protocol Layers Map data to the ATM cell structure Framing, cell structure & Logical Connections Various data rates (155.52 Mbps, 622.08 Mbps) over various physical media types (Fiber Optic, SONET, UTP, etc.) DEEPAK.P 42

  43. ATM layers DEEPAK.P 43

  44. Physical layer It involves the specifications of a transmission medium and signal encoding scheme. Two Sublayers: Transmission Convergence (TC) Framing HEC Physical Media Dependent (PMD) Physical media coding DEEPAK.P 44

  45. ATM layer It involves in the Packet transfer Transmission of data in fixed size cells It defines the use of logical connections DEEPAK.P 45

  46. ATM Adaptation layer AAL encapsulates user-level data Performs segmentation and reassembly of user-level messages Data Data AAL AAL reassembly segmentation ATM Network Cells Cells DEEPAK.P 46

  47. AAL Layer The main services provided by AAL (ATM Adaptation Layer) are: Segmentation and reassembly Handling of transmission errors Handling of lost and mis inserted cell conditions Timing and flow control AAL is divided into the Convergence Sub layer (CS) and the Segmentation and Reassembly (SAR) Sub layer DEEPAK.P 47

  48. ATM adaptation layer DEEPAK.P 48

  49. ATM adaptation layer AAL Convergence Sub layer is divided in to DEEPAK.P 49

  50. ATM adaptation layer Four AAL protocols have been defined to support four AAL service classes AAL service classes Class A Class B Class C Class D AAL protocols AAL 1 AAL 2 AAL 3/4 AAL 5 DEEPAK.P 50

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