ed by several infrastructure owners and associated whole- salers. The business system diagram is completed by the equipment manufacturers and retailers chain. The infrastructure value includes provision of a telecommunications link with a designed level of service quality to a subscriber. The link may be fixed and exclusive to one user, as in an FTTP (fibre to the premises) link. Or it may be shared, as in mobile tele- communications systems. The telecommunications ecosystem may be defined as a 'pipe' business, where the information transferred over the network is user-generated. Examples may be a phone call between two parties, or an email exchanged through two computers, as illustrated in Figure 14.2. The role of infrastructure/retail operators is to provide a link to carry this end-user generated content, and charge subscribers for the connectivity service. Historically, the vast part of operators' revenue has come from this 'pipe' business. Different revenue models exist: the fee may be calculated per minutes of a voice call or the size/number of transferred data packets. Other sources of revenues may include a Subscriber Capacity retail Service Retailer operator Device Capacity wholesale wholesale Device Core network manufacturer operator Figure 14.1 Business system diagram for a telecommunications infrastructure business Content Delivery and Net Neutrality fixed monthly subscription fee. These added together and averaged for all subscribers result in a widely used metric for operators' performance, known as average revenue per user (ARPU). This metric is commonly used to evaluate the performance of a fixed or a mobile operator both in an absolute fashion as well as Content and services layer relative to their competitors. Another kind of traffic that flows over a telecom- munications infrastructure is associated with third Connectivity retail layer party content and services. Such content may originate from within the operator network or be provided by Infrastructure layer a third party as illustrated in Fi