I wanted to know how ATM machines are interconnected all over the globe ... is it connected in a way similar to the internet structure ? Does it rely on the internet at any point ? Not so clear about it ... will appreciate a detailed reply
Usually ATM networks don't need interconnection over the globe. They covers some region for providing access there. But interact with other ATM networks, that located in other word regions, it can through other data networks (Internet).
For this purpose is used LANE protocol (LAN Emulation). Interconnection ATM with Internet (IP network) fulfils with router, that maintains this technology.
Let me expand on what alexndr posted. An ATM connection, usually copper but can also be used over fibre, is more reliable than say ADSL over copper. It has to do with the way the ATM protocol works. Anyhow, these ATM connections usually travel over the PSTN infrastructure to the local bank or the nearest regional bank. From there everything is transported over the internet via dedicated internet connections that are reliable with a high SLG(Service Level Gauantee)