Asynchronous Transfer Mode (ATM) is a telecom standard that was defined and standardized by ANSI and ITU. It was developed in the late 1980s and was designed to be capable of handling voice, video, and high throughput data traffic in such a way as to accommodate the sensitive real-time nature of these types of traffic. ATM functions at the Data Link Layer, or Layer 2 of the OSI model. It is primarily used as a backbone technology, as well as a WAN technology. ATM has generally not been very popular for the past 15 years, and is steadily being phased out in favour of other technologies including MetroEthernet, MPLS, and others.
An ATM switch is a switch that supports the ATM standard. I’m surprised that there are still such devices and implementations being used today, it would be interesting to find out more about why they are still in use… Can you give us some more info about this particular implementation, without revealing any specific information about the ISP or customer?
I hope this has been helpful!