BNR's products were architecturally based on Complex Instruction Set (CISC) architectures prevalent in the 1970s, and on a series of underlying technologies. This was greatly influenced by the late 1970s success of the DEC VAX computer, a highly "elegant" and rather layered technology, realizable in a range of power. In the early 1990s, under Nortel CEO Jean Monty, the software for the flagship DMS product was segmented into layers ('Base', 'Telecom', and 'IEC' or Inter-Exchange Carrier) to improve maintainability of the product. The IEC layers were customer-specific, targeted towards Sprint, MCI, and a large group of small "United Carrier" companies that were subsequently swallowed up by Worldcom. Once the IEC layer was established, customer-specific releases could occur quarterly, whereas Telecom and Base programming was for baked-in code that only had infrequent, maintenance updates.