Asynchronous Transfer Mode (ATM) is a networking technology used for transmitting data, voice, and video over a network. ATM is known for its high-speed transmission, low delay, and low jitter. It is often used in large networks such as in businesses, universities, and governments due to its efficiency and reliability.

For a beginner, learning about ATM can seem overwhelming, but this guide will provide you with the foundational knowledge to get started.

ATM Architecture

The ATM architecture consists of hardware and software components. The hardware includes switches, routers, and network adapters, while the software includes the protocols and interfaces that allow communication between devices.

Virtual Circuit

ATM uses virtual circuits, which are logical connections between two or more devices. Virtual circuits can be either permanent or switched. Permanent virtual circuits (PVCs) are pre-established and serve as a dedicated connection between devices. Switched virtual circuits (SVCs) are established on-demand and are used for occasional data transfer between devices.

ATM Cell

The basic unit of data transmission in ATM is the ATM cell. ATM cells are 53 bytes long and consist of five parts: header, payload, checksum, and a virtual channel identifier (VCI) and virtual path identifier (VPI). The VCI and VPI are used to identify the virtual circuit over which the cell is transmitted.

Quality of Service (QoS)

ATM provides Quality of Service (QoS), which ensures that data transfer is efficient and reliable. QoS includes priority settings, traffic shaping, and bandwidth allocation to ensure that important data is transmitted first and that data transfer does not overwhelm the network.

ATM Signaling

ATM signaling is used to establish and maintain virtual circuits. Several signaling protocols exist, including UNI (User-Network Interface) and NNI (Network-Network Interface). UNI signaling is used between end devices and a switch, while NNI signaling is used between switches.

ATM Switching

ATM switches are used to forward ATM cells from one virtual circuit to another. Switches use the VCI and VPI to determine the correct virtual circuit to forward the cell. ATM switches can be either centralized or distributed, with distributed switches being more common.

ATM Application

ATM is used in various applications, including Voice over IP (VoIP), video conferencing, internet access, and LAN interconnection. ATM is used in businesses and organizations that require high-speed and reliable data transfer.

Conclusion

ATM is a powerful networking technology that provides high-speed and reliable data transfer. By understanding the basic concepts of ATM architecture, virtual circuits, ATM cells, QoS, signaling, switching, and applications, you can begin to explore and use ATM technology in your network environment.