This paper presents a novel peer-to-peer structure overlay network SmartBoa. Compared to previous protocols, SmartBoa nodes have routing tables with different sizes, which are determined by the local nodes individually. It is ensured that the bandwidth cost of a node is proportional to its routing table size. Therefore, from the view of the whole system, all the allowable bandwidth are fully utilized to improve the routing efficiency. SmartBoa does not increase the capacity requirement for nodes when the system expands, so it can achieve higher scalability than the one-hop protocol. Furthermore, SmartBoa nodes can adjust its level at runtime, and thereby can warm up gradually when starting. This avoids the long-time initiation which is an important problem in one-hop overlay. In a word, SmartBoa is a general structure overlay network that can be deployed in any environments, not matter what the system size is, how dynamic the nodes are, and what the node-capacity distribution is like.