asynchronous transfer mode (atm)


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asynchronous transfer mode (atm)

  1. 1. Asynchronous Transfer Mode (ATM)
  2. 2. By. P. Victer Paul Dear, We planned to share our eBooks and project/seminar contents for free to all needed friends like u.. To get to know about more free computerscience ebooks and technology advancements in computer science. Please visit.... Please to keep provide many eBooks and technology news for FREE. Encourage us by Clicking on the advertisement in these Blog.
  3. 3. Agenda <ul><li>Definition </li></ul><ul><li>Basic characteristics </li></ul><ul><li>Why asynchronous </li></ul><ul><li>How to access the network </li></ul><ul><li>Service Categories </li></ul><ul><li>Connections </li></ul><ul><li>Protocol Architecture </li></ul><ul><li>pros & cons </li></ul><ul><li>Troubleshooting </li></ul>
  4. 4. ATM – definition <ul><li>&quot;A transfer mode in which information is organized into cells; it is asynchronous in the sense that the recurrence of cells containing information from an individual user is not necessarily periodic&quot;. </li></ul>
  5. 5. ATM Characteristics <ul><li>ATM uses packet switching with fixed length packet of 53 bytes – CELLs. Each cell has a 5-byte header and 48-byte payload </li></ul><ul><li>ATM uses Virtual Circuits </li></ul><ul><li>ATM can run over any physical layer. Often runs over fiber optics using the SONET standard at speeds of 155.52 Mbps, 622 Mbps and higher </li></ul>
  6. 6. ATM Characteristics <ul><li>A Cell network uses the cell as the basic unit of data exchange. A cell is defined as a small, fixed-sized block of information </li></ul><ul><li>ATM uses asynchronous TDM – to multiplex cells coming from different channels </li></ul><ul><li>Uses fixed slots (size of cells) </li></ul><ul><li>Fills a slot with a cell from any input channel that has a cell </li></ul><ul><li>– slot is empty if none of the channels has a cell to send </li></ul>
  7. 7. Asynchronous Transfer Mode (ATM) MUX Wasted bandwidth 4 3 2 1 4 3 2 1 4 3 2 1
  8. 8. ATM Access <ul><li>ATM is a cell-switched network. </li></ul><ul><li>The user access devices, called the endpoints, are connected through a user-to-network interface (UNI) to the switches inside the network. </li></ul><ul><li>The switches are connected through network-to-network interfaces (NNIs). </li></ul>
  9. 9. STDUCTURE X X X X X X X X X Private UNI Public UNI NNI Private NNI Private ATM network Public UNI B-ICI Public UNI Public ATM network A Public ATM network B
  10. 10. ATM Connections <ul><li>two levels of ATM connections: </li></ul><ul><li>virtual path connections </li></ul><ul><li>virtual channel connections </li></ul><ul><li>indicated by two fields in the cell header: </li></ul><ul><li>virtual path identifier VPI </li></ul><ul><li>virtual channel identifier VCI </li></ul>
  11. 11. Physical Link Virtual Paths Virtual Channels
  12. 13. ATM Service Categories <ul><li>Real-time services </li></ul><ul><ul><li>Constant bit rate – uncompressed audio/video info </li></ul></ul><ul><ul><ul><li>Videoconferencing, TV, pay-per-view, VOD, etc. </li></ul></ul></ul><ul><ul><li>rt-Variable bit rate </li></ul></ul><ul><li>Non-real-time services </li></ul><ul><ul><li>nrt-VBR – high end system QoS, critical response time </li></ul></ul><ul><ul><ul><li>Bank transactions, airline reservations, etc. </li></ul></ul></ul><ul><ul><li>Unspecified bit rate – best-effort service </li></ul></ul><ul><ul><ul><li>e.g. text/image messaging, telecommuting </li></ul></ul></ul><ul><ul><li>Available bit rate – bursty apps requiring reliable end-to-end connection </li></ul></ul><ul><ul><ul><li>e.g. LAN, router-to-router reliability </li></ul></ul></ul>
  13. 14. ATM Protocol Architecture Plane management Management plane Control plane User plane Physical layer ATM layer ATM adaptation layer Higher layers Higher layers Layer management
  14. 15. <ul><li>adaptation layer: only at edge of ATM network </li></ul><ul><ul><li>data segmentation/reassembly </li></ul></ul><ul><ul><li>roughly analogous to Internet transport layer </li></ul></ul><ul><li>ATM layer: “network” layer </li></ul><ul><ul><li>cell switching, routing </li></ul></ul><ul><li>physical layer </li></ul>Physical layer ATM layer AAL user
  15. 16. Pros & cons <ul><li>higher transmission speeds </li></ul><ul><li>quality of service </li></ul><ul><li>bandwidth-on-demand </li></ul><ul><li>application-independent </li></ul><ul><li>Cost </li></ul><ul><li>Complexity </li></ul><ul><li>Availability </li></ul>
  16. 17. Troubleshooting <ul><li>Performing Basic Interface Checks </li></ul><ul><li>Determining Network Connectivity </li></ul><ul><li>Performing Loopback Tests </li></ul><ul><li>Troubleshooting 155-Mbps and 622-Mbps Interfaces </li></ul><ul><li>Troubleshooting T1 and E1 Interfaces </li></ul><ul><li>Troubleshooting DS3 and E3 Interfaces </li></ul><ul><li>Troubleshooting CBR T1 and CBR E1 Interfaces </li></ul><ul><li>Troubleshooting 25-Mbps Interfaces </li></ul>
  17. 18. References: <ul><li>Asynchronous Transfer Mode (ATM) fundamentals, white paper from Internation Engineering Consortium </li></ul><ul><li>ATM tutorial-fnc educational services </li></ul><ul><li>Higher Layer Protocols:TCP/IP and ATM- Eytan Modiano,Massachusetts Institute of Technology </li></ul><ul><li>ATM Switch Troubleshooting Guide-Cisco </li></ul>