(1) When written as AToM, it is short for Any Transport over MPLS, a technology developed by Cisco for transporting Layer 2 packets over an IP/MPLS backbone. The technology is designed to let ISPs combine multiple disparate data networks — such as Ethernet, ATM, Frame Relay, and Serial/PPP networks — onto a single MPLS-based backbone to save operational costs. AToM is sometimes called Layer 2 MPLS.
(2) Atom is the name of an XML-based Web content and metadata syndication format, and an application-level protocol for publishing and editing Web resources belonging to periodically updated Web sites. All Atom feeds must be well-formed XML documents, and are identified with the application/atom+xml media type. [Source: AtomEnabled]