ATM (Asynchronous Transfer Mode)
ATM is a 1990s technology which was heavily deployed by wide area networking vendors. ATM has built-in sophisticated QoS mechanisms that do a good job of separating traffic.
Much of the technology for measuring and policing bandwidth flows was developed by the ATM Forum during the initial days of ATM deployment. These techniques are used today in DiffServ and MPLS implementations.
ATM service categories are not the same as DiffServ categories, but the DiffServ categories can be mapped into ATM categories at the network boundary. Table 3 shows the mapping between DiffServ code points and ATM service categories.
Enterprises using ATM within the corporation can use this QoS mechanism as well. Larger enterprises have ATM backbones between major sites. ATM QoS will give priority to classes higher on this list.