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Understanding Asynchronous Transfer Mode (ATM) in Telecommunications

This article explores the fundamentals of Asynchronous Transfer Mode (ATM), a versatile network technology used in both local and wide area networks. It discusses the differences between Synchronous Transfer Mode (STM) and Packet Transfer Mode (PTM), highlighting their advantages and disadvantages for data transmission. ATM combines the benefits of both modes, allowing efficient transmission of voice, video, and data while accommodating diverse bandwidth requirements. With its ability to establish logical circuits and guarantee quality of service, ATM remains a vital backbone in modern telecommunications.

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Understanding Asynchronous Transfer Mode (ATM) in Telecommunications

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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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