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ASYNCHORONOUS TRANSFER MODES

ASYNCHORONOUS TRANSFER MODES. Points to be discussed are :. Definition ATM standard ATM network ATM interfaces ATM cell ATM Adaptation layer(AAL) to be contd. ATM Application ATM Services Categories ATM advatages ATM advantages

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ASYNCHORONOUS TRANSFER MODES

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  1. ASYNCHORONOUS TRANSFER MODES

  2. Points to be discussed are: Definition ATM standard ATM network ATM interfaces ATM cell ATM Adaptation layer(AAL) to be contd...

  3. ATM Application • ATM Services Categories • ATM advatages • ATM advantages • ATM challenges • References

  4. ATM-Definition • Asynchronous Transfer Mode (ATM) is a technology that has the potential of revolutionizing data communications and telecommunications. • ATM is a packet switching.

  5. What is it really? Low-level network layer Single transport mechanism Streamlined protocol

  6. ATM Standard • ITU-T I.361 • Defines the ATM Layer functions. • ITU-T I.363 • Defines the ATM Adaptation Layer- protocols. • ITU-T I.610 • Defines the ATM Operation and Maintenance (OAM) functions

  7. The ATM network • 1) User-to-Network Interface (UNI) • 2) Network-to-Network Interface (NNI) • 3) Inter-Carrier Interface (ICI)

  8. ATM Interfaces 1. User-to-Network Interface (UNI) • Exists between a single end user and a public ATM network. 2.Network-to-Network Interface (NNI) • Exists between switches in a single public ATM network. 3. Inter-Carrier Interface (ICI) • It is located between two public ATM networks

  9. Important parameters • Virtual channel: • A channel that provides transportation of ATM cells between two or more endpoints for information transfer. • Virtual paths: • It is a group of Virtual Channels that are carried on the same physical facility and share the same Virtual Path Identifier (VPI) value.

  10. ATM cells Diagram of the NNI ATM Cell Diagram of the UNI ATM Cell Small size, may reduce queuing delay of high priority cells Fixed size, more efficient switching

  11. ATM cell content 1) 5 bytes header: (I) General flow control • defined across the UNI • flow across the UNI • intended to control the traffic • 4 bits must be set to 0's. (II) Virtual path control • routing field for network • an 8-bit field for the UNI and a 12-bit field for the NNI, is used to identify virtual paths.

  12. Continue…. • Virtual Channel Identifier (VCI) • 16-bit field is used to identify a virtual channel • For idle cells, the VCI is set to all 0's. • Payload Type Identifier (PTI) • three bits of the PTI

  13. Cell Loss Priority (CLP) • The 1-bit CLP field • used for explicit indication of the priority of the cell • Header Error Control (HEC) • 8-bit fieldIt capable of detecting all single-bit errors and some multiple-bit errors.

  14. ATM Applications

  15. ATM Service Categories • Real-time services • Constant bit rate – uncompressed audio/video info Videoconferencing, TV, pay-per-view, VOD, etc. • Non-real-time services • Available bit rate – bursty apps requiring reliable end-to-end connection e.g. LAN, router-to-router reliability

  16. ATM Advantages • Universality • Mixed traffic types, real-time and non-real- time • Scalability • LANs, WANs, WLANs • Efficient use of network resources Bandwidth on demand concept • Simplified network infrastructure

  17. ATM challenges • In-network mux/buffering can lead to cell delay or loss • Many types of traffic • Large geographic distribution

  18. References • http://www.iec.org • Amos E. Joel, Jr., Asynchronous Transfer Mode (IEEE Press, 1993) • "Broadband ISDN and ATM". http://world-class-programme.com

  19. THANK YOU

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