Average per-bit delivery cost
Average Per-Bit Delivery Cost averages the cost of however many bits were actually sent or received across a link with the actual cost of operation of the link. This is contrasted principally with flat-rate and 95th percentile functions, which are typically used for billing rather than cost-accounting. In typical use, APBDCs of individual links or components of an operating network are compared with the APBDC of the whole, in order to evaluate the efficiency of the components, and to track improvements in effectiveness.
High APBDC may reflect either a high cost, or a low utilization, either of which is detrimental to the price-performance of the network as a whole, and indicates an area that needs attention and improvement. Besides reduction in costs of existing network components, use of already-amortized or less expensive components, and transmission of greater volumes of traffic, fundamental or "revolutionary" changes to the topology of a network, such as the substitution of peering-derived bandwidth for purchased transit, often have substantial impacts on a network's APBDC.