Atm and Its Use

ATM and Its Use

Introduction

Asynchronous Transfer Mode is a cell-based switching technique, designed for high speed networks, such as LAN, WAN and can support multiple service types, such as voice, video, or data. It is connection-oriented, and uses asynchronous time-division multiplexing technology. ATM creates a virtual circuit between two endpoints across its switching fabric before the actual data exchange starts.

ATM is based on the efforts of the ITU-T Broadband Integrated Services Digital Network (B-ISDN) standard. It uses small fixed-sized cells (53 bytes) over public and private networks, and provides guaranteed capacity and constant transmission delay compared to IP which uses variable sized packet. Not just this, ATM has many other advantages and can be sum up as follows:

• Using best effort delivery system

• Adopting bandwidth on demand

• Integrates Voice, Video and Data

• Using short fixed length packets called cells

• Connection Oriented

• Compatibility- ATM is compatible with many currently deployed physical layers: such as twisted pair, coax and fiber.

ATM Cell

Like mentioned before, ATM is constructed of 53-byte cells, which includes a 5-byte header and a 48 bytes payload. Figure1 shows the detail format of the ATM cell.

|5 Bytes Header |48 bytes Header |

|Generic flow header |Virtual path identifier (VPI) |

|Virtual path identifier (VPI) |Virtual channel identifier (VCI) |

|Virtual channel identifier (VCI) |

|Virtual channel identifier (VCI) |Payload type |CLP |

|Header Error Control...