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ASYNCHORONOUS TRANSFER MODES

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ASYNCHORONOUS TRANSFER MODES. Points to be discussed are: Definition. ATM standard. ATM network. ... Single transport mechanism. Streamlined protocol. ATM Standard. – PowerPoint PPT presentation

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Title: ASYNCHORONOUS TRANSFER MODES


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
  • Small size, may reduce queuing delay of high
    priority cells
  • Fixed size, more efficient switching

Diagram of the NNI ATM Cell
Diagram of the UNI ATM Cell
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-prog
    ramme.com

19
THANK YOU
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