Asynchronous Transfer Mode (ATM) was a WAN technology that used a combination of cell-based technology and SONET. ATM used 53-byte cells spaced evenly apart, which contained the following:
- 48 bytes for data
- 5 bytes for the routing header
These cells were transmitted into a constant stream over the network and traffic was transmitted at a high throughput with low latency, no matter whether data, voice, or video was sent. ATM offered throughput up to OC-192, but one disadvantage was that traffic had to be segmented due to the small available cell size. This meant that the effort had to be doubled at the receiving end, where packet reassembly had to occur. Other ATM disadvantages include the following:
- Complex installation and configuration
- Expensive ATM network equipment
All of these disadvantages led to the ATM technology being replaced by cheaper and more efficient technologies.