What are the units called that transport asynchronous transfer mode (ATM) data?

The correct term for the units that transport asynchronous transfer mode (ATM) data is "cells." In ATM technology, data is divided into fixed-size cells, each consisting of 53 bytes: 48 bytes for the payload (the actual data) and 5 bytes for the header (which contains routing and control information).

This structure is key to ATM's ability to efficiently handle various types of traffic, such as voice, video, and data, while providing a constant delay and bandwidth for real-time applications. The fixed cell size helps reduce the complexity of switching and makes the protocol well-suited for high-speed networks.

While terms like frames, packets, and segments are used in various other networking contexts, they refer to different types of data units in different protocols. Frames pertain to data link layer protocols like Ethernet, packets are associated with the network layer, and segments are used in the transport layer, especially in TCP/IP networks. Each of these units has distinct structures and purposes that differ from the ATM cell.