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Telecommunication Systems Spring 2010 PowerPoint PPT Presentation


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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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Telecommunication systems spring 2010

Telecommunication Systems

Spring 2010


Telecommunication systems spring 2010

synchronous

ransfer

ode

A

T

M


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

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.


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • Asynchronous Transfer Mode?


Telecommunication systems spring 2010

ATM

  • ATM combines the STM and PTM

  • ATM can transfer data of any type, any bandwidth and any frequency


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • ATM basic network architecture

    • ATM can be used for the inter-connection of local data networks


Telecommunication systems spring 2010

ATM

  • ATM Network Architecture


Telecommunication systems spring 2010

ATM

  • ATM Switch


Telecommunication systems spring 2010

ATM

  • ATM Principles??

    • Any type of information is divided into fixed size packets and then transmitted


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • ATM Principles??

    • ATM cells are generated only when required

    • Available bandwidth is exploited flexibly to meet the challenging requirements


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • Information Packing !!

    • Information is packed into cells in order to be transmitted

    • Irrespective of the service, all cells have the same size


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • ATM Connections !

    • Cells are routed using the identifier in the cell header

    • All cells of a connection take the same route


Telecommunication systems spring 2010

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


Telecommunication systems spring 2010

ATM

  • ATM Connections !


Telecommunication systems spring 2010

Thank You


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