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The AS path prepending approach in BGP is commonly used to perform inter-domain traffic engineering, such as inbound traffic load-balancing for multi-homed ASes. It artificially increases the length of the AS level path in BGP announcements by inserting its local AS number multiple times into outgoing EBGP announcement messages. In this work, we first present a comprehensive study on the characterization of Internet routing AS path prepending. We further propose an algorithm for computing the optimal padding strategies given multiple neighboring links. Our method considers the impact of AS relationship based local policies on ASPP's effectiveness. The algorithm can be used for three objectives, i.e., traffic load balancing, backup route provisioning, and bypassing a specific AS for security purposes, e.g., avoiding information censorship. We demonstrate the accuracy and effectiveness of our approach using real BGP data and traffic data from Abilene networks.