In carrier networks, the appliance model is giving way to a disaggregated model. Traditionally, functions like routing were implemented in a tightly coupled hardware and software bundle. Routing vendors could ensure the proper operation of their system because they controlled the entire network element. They even developed their own switching ASICs for their line cards.
Total Cost of Ownership (TCO) is a familiar concept – it recognizes that the acquisition cost is only part of the cost story. Think about a car. You have the purchase price (or the lease). In addition, there are the costs incurred over the life of the vehicle such as fuel, maintenance, insurance and licensing.