Virtual private networks (VPNs) have rapidly emerged as a leading solution for multi-site enterprise communication needs. Provider-managed solutions modeled on RFC 2547 serve as a popular choice for layer 3 VPNs, and the hose model has emerged as a common and simple service specification. It offers a hose of a certain contracted bandwidth to customers. With the growth in size and number of VPNs and the uncertainties in the traffic patterns of customers, providers are faced with new challenges in efficient provisioning and capacity planning for these networks and satisfying customer service level agreements (SLA). We suggest that a set of techniques can be used to help the provider build an adaptively provisioned network. These techniques involve continually processing measurement information, building inferences regarding VPN characteristics, and leveraging them for adaptive resource provisioning. We developed scalable techniques to infer VPN characteristics that are important for provisioning tasks. We demonstrated the feasibility of such provisioning techniques with existing measurement obtained using SNMP infrastructure from a large IP/VPN service provider. Our examination of measurement data yielded interesting new insights into VPN structure and properties. Building on our experience with analyzing VPN characteristics, we articulate an adaptive provisioning architecture that enables providers to effectively deal with the dynamic nature of customer traffic