 and to create a private company telephone network. This kind of offering still exists for companies having its own switches and desiring a complete isolation of its internal network. However, the leasing of a whole physical line is a costly solution and many companies prefer to lease a given capacity, multiplexed on the Telecommunication Networks physical lines via statistical multiplexing with other signals. In this way, the exploitation efficiency of the physical line is much bigger and rent prices are smaller. Renting a virtual capacity opens two problems: assuring both an agreed SLA via a QoS monitoring and data privacy even if they are statistically multiplexed with other data. Both these problems are solved using the concept of virtual private network (VPN) [23]. A VPN is implemented enveloping the packets belonging to this virtual network in a pub- lic envelop before being injected into the public network. This public envelop masks com- pletely all the characteristics of the packet (such as the specific destination, the nature of the service, and SO on), and simply reports the address of the destination within the public network (i.e., the last public node of the packet path) and a set of other data related to the SLA and the QoS. The concept of VPN has been a really fruitful idea, since it has been used for several applications also different from its original rationale, for example, to manage QoS in car- rier class Ethernet networks. Last, but not least, a carrier managing its own network delivers wholesale services to other carriers. Wholesale services consist in renting transmission capacity to other carriers in terms either of physical trunk (like copper pairs in the access network) or logical capacity within a multiplexed signal. Wholesale services can be classified into regulated and unregulated services. Regulated services are provided in Europe and in the United States by the incumbent carriers to the competitive carriers in order to allow them to carry out their business. The main regulated whol