Short for inverse multiplexing over ATM. IMA is a physical layer technology in which a high-speed stream of ATM cells is broken up and transmitted across multiple T1/E1 links, then is reconstructed back into the original ATM cell order at the destination. For companies with low to mid-range WAN requirements, the purchase of costly T3/E3 access is not a viable solution. IMA divides an aggregate stream of ATM cells across multiple T1/E1 WAN links on a cell-by-cell basis, mimicking the behavior of transmissions across T3/E3 lines.
IMA is a User-to-Network Interface standard approved by the ATM Forum in 1997.