of coexisting interface variations. There is a great number of interfaces present in OSS/BSS systems. For simplicity, however, only four interfaces implemented by the mediation software subsystems are considered below: Market Polarization due to Difference in Interface Implementation Efforts Charging: (1) collection interface between Mediation and Network Elements (NEs), and (2) charging interface between Mediation and Billing Systems (also fraud, revenue assurance, dataware, interconnect etc. systems) Configuration: (1) configuration interface between Mediation and NEs; (2) activation interface between Mediation and Service Order Management System (e.g., inside CRM, Billing, sales applications) In order to estimate the efforts, the data has been obtained through various data collection techniques including the analysis of the Dittberner Associates' OSS/BSS Knowledgebase, documentation by TM Forum, and other publicly available web- sources, and has been complemented with the data gathered through interviews. According to the data, a few dozens of the protocol types and over three hundred interface variations need to be supported by the mediation software vendor if the software is offered to incumbent operators. Based on the available data, the interface implementation efforts (in person- years) have been estimated. The results of the estimation are shown in Fig. 1, wherein the efforts of interface implementation are shown for two cases: All types of interfaces are supported (dashed line). Only interfaces based on standard IETF protocols (RADIUS, LDAP, HTTP, SOAP, etc.) are supported (solid line). When serving the incumbent operators, all interface types need to be implemented; the corresponding efforts by a vendor in this case are shown by the dashed line. On the other hand, to serve new operators, the vendor may have to implement only a (IETF) subset of the protocols; these efforts are shown by the solid line. The total efforts in the first case are ca. 32 times greater than the efforts in the second case. The e