But ATM is a different story. ATM is a truly revolutionary technology, not because frames are broken down into small cells, but rather for the way it handles data and data paths. It turns out that ATM's virtual circuits are a natural mechanism for supporting virtual LANs over a backbone. LAN emulation is the key to making this happen today. Each time a packet comes by a bridge, the bridge determines what to do with the packet by looking at the source and destination address in the packet header.
Routers do the same with each packet's network layer information.
The process is repetitive and consumes time and valuable resources. With ATM, the data path determination and data transmission are separate. When a station wants to communica te with another, it requests a connection to the destination and starts sending data once the data path is established. As long as there will be some reasonable amount of data transmitted, any burden created by separating the path discovery from data transmission is outweighed by efficiencies in using the discovered path. But there is just too much legacy networking to expect that ATM will be adopted lock, stock and barrel.