Acronym/Abbreviation: ATM – Asynchronous Transfer Mode
Asynchronous Transfer Mode (ATM) is a high-speed networking technology that was developed in the late 1980s and early 1990s. It was designed to support the simultaneous transmission of voice, video, and data over the same network infrastructure while providing high-quality service and low latency.
Here are the key features and aspects of ATM:
- Cell-Based: ATM uses fixed-size cells for data transmission. Each cell is 53 bytes in length, with 48 bytes for data and 5 bytes for the header. The fixed cell size simplifies switching and routing in the network.
- Virtual Circuits: ATM establishes virtual circuits between endpoints. There are two types of virtual circuits: Permanent Virtual Circuits (PVCs) and Switched Virtual Circuits (SVCs). PVCs are pre-configured and dedicated, while SVCs are set up on-demand.
- Quality of Service (QoS): One of the defining features of ATM is its support for QoS. It offers several service categories to accommodate different types of traffic, including Constant Bit Rate (CBR), Variable Bit Rate (VBR), Available Bit Rate (ABR), and Unspecified Bit Rate (UBR). This allows ATM to guarantee certain levels of bandwidth and latency for real-time applications like voice and video.
- Scalability: ATM networks can scale from low speeds (e.g., 1.5 Mbps) to very high speeds (e.g., 10 Gbps or more). This scalability made ATM attractive for both small-scale and large-scale networks.
- Broadband ISDN: ATM was initially developed as the core technology for Broadband Integrated Services Digital Network (B-ISDN), which aimed to provide high-speed, integrated communication services.
- Adaptation Layers: ATM provides Adaptation Layers (AALs) to support different types of data and traffic. For example, AAL1 is used for constant bit rate services like voice, while AAL5 is used for data services.
- Legacy Technology: ATM was widely used in the 1990s and early 2000s, especially for wide area networking and certain enterprise applications. However, it has largely been replaced by other technologies, such as Ethernet and IP/MPLS, for many network applications.
- Legacy Infrastructure: Some telecommunications providers still maintain legacy ATM networks, particularly for carrying legacy voice and data services.
- ATM Forum: The ATM Forum was a consortium of companies that developed and promoted ATM standards. It played a significant role in the development and standardization of ATM technology.
In summary, ATM was a pioneering networking technology known for its support of multiple traffic types and quality of service guarantees. While it has seen reduced use in recent years, its influence on the development of networking concepts and protocols remains significant.