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Telecommunication Systems Spring 2010

Telecommunication Systems Spring 2010. synchronous ransfer ode. A. T. M. ATM. What is a Transfer Mode ? The way an information is transferred over the network Synchronous Transfer Mode (STM)

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Telecommunication Systems Spring 2010

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  1. Telecommunication Systems Spring 2010

  2. synchronous ransfer ode A T M

  3. ATM • What is a Transfer Mode? • The way an information is transferred over the network • Synchronous Transfer Mode (STM) • In this mode, the information is transferred as soon as it is generated (without any delay), as a continuous stream of data • Best suited for speech, video and other real time applications which can not afford delays in transmission • Restricted to a fixed (allocated) bandwidth

  4. ATM • What is the advantage/disadvantage of fixed bandwidth?? • Dedicated for a connection (always available). Suited for constant bit rate applications • Can not be shared/used by another connection when free • Inflexible for variable bit rate applications (multimedia applications) • Inefficient bandwidth utilization

  5. ATM • Packet Transfer Mode (PTM) • In this mode the bursts of data are packed and then transferred over the network • Packing of data causes delay in transmission • Suited for applications that can afford delay, for example file transfer, LAN communication etc.

  6. ATM • What is the advantage with PTM? • Efficient bandwidth utilization • What is the disadvantage with PTM? • Packets of variable length, not suited for constant bit rate applications • Each packet may take a separate path to the destination • More processing is involved at intermediate routers so more delay

  7. ATM • Asynchronous Transfer Mode?

  8. ATM • ATM combines the STM and PTM • ATM can transfer data of any type, any bandwidth and any frequency

  9. ATM • The term Asynchronous?? • The data rates to be transmitted need not comply with a specific bandwidth • The transmission is only performed if there is data to be transmitted • No bandwidth is occupied when there is no data to be transmitted

  10. ATM • Asynchronous Transfer Mode? • A network technology for both local and wide area networks that supports real time voice, video as well as data • The technology uses switches that establish a logical circuit from end to end, and guarantees quality of service • ATM is widely used as a backbone technology in carrier networks and large enterprises

  11. ATM • Asynchronous Transfer Mode? • ATM is highly scalable and supports transmission speeds of 1.5, 25, 100, 155, 622, 2488 and 9953 Mbps • Basic Network Architecture

  12. ATM • ATM basic network architecture • ATM can be used for the inter-connection of local data networks

  13. ATM • ATM Network Architecture

  14. ATM • ATM Switch

  15. ATM • ATM Principles?? • Any type of information is divided into fixed size packets and then transmitted

  16. ATM • ATM Principles?? • The information is packed and transmitted right away, without delay • As compared to STM, ATM has advantage that the transmission rates can be varied

  17. ATM • ATM Principles?? • ATM cells are generated only when required • Available bandwidth is exploited flexibly to meet the challenging requirements

  18. ATM • ATM Principles?? • If a user wants to call a multimedia application, the following bandwidth is required • Even within an application, only the required amount of bandwidth is provided

  19. ATM • Information Packing !! • Information is packed into cells in order to be transmitted • Irrespective of the service, all cells have the same size

  20. ATM • Information Packing !! • The information field is also known as payload • It transmits the segmented user information • The cell header main task is to route the ATM cell through the ATM network

  21. ATM • ATM Connections ! • Prior to the transmission of payload, a connection must be setup via subscriber signaling • Payload is then transmitted via this connection • The connection is cleared down again via subscriber signaling

  22. ATM • ATM Connections ! • Cells are routed using the identifier in the cell header • All cells of a connection take the same route

  23. ATM • ATM Connections ! • Path of a connection through the ATM network is specified, no physical resources are reserved, because the bandwidth of the connection must be flexible • If channels were reserved, the information would be restricted to a fixed bandwidth • Connections established without reservation of physical resources are called virtual ATM connections

  24. ATM • ATM Connections !

  25. Thank You

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