Design of a charging and accounting architecture for QoS-differentiated VPN services to mobile users

In the emerging context of mobile Internet, the importance of VPN services is rapidly increasing. Provision of such services was among the subjects of IST project INTERNODE. Besides the necessary technical means, charging and accounting also are key related issues, and constitute the subject of this paper. Only by dealing successfully with charging and accounting, VPN providers can recover their provision costs, increase their profits, and provide the right incentives to their users, thus leading to efficient operation of their network. In this paper, we first study the chargeable characteristics of QoS-differentiated VPN services offered to mobile users with respect to transport, security and mobility (both personal and terminal). Then, we define a complete charging scheme that is fair for the users and provides them with the incentives to use only the resources they really need. This scheme is based on the time-volume charging approach by Kelly; the adoption of this approach is justified in detail. We then show how the providers involved can share the total charge earned by each VPN service instance in a fair way, with each provider collecting the portion of charge that corresponds to the consumption of his own resources for the service. This is also a very important issue for the commercial viability of VPN services to mobile users, given that its provision spans multiple domains. Our approach also includes computation of an estimate of users’ expected charge prior to using the VPN service. Finally, we specify an appropriate charging and accounting architecture pertaining to the specified charging scheme for VPNs, to the mechanism for revenue sharing, and to the technical implementation of the VPN services studied. This architecture is compliant to the relevant standards, is applicable to the current and the future Internet, was fully implemented, and can serve as a basis for applying other charging schemes as well. Our work can also serve as a methodology for designing charging and accounting architectures for a variety of Internet services.