Routing Indices (RIs) are introduced to improve the efficiency of content search in peer-to-peer (P2P) systems. Traditional methods either use a costly central index or flood the network with queries, which is inefficient. RIs allow nodes to forward queries to neighbors more likely to have answers, improving performance significantly. Three RI schemes are proposed: compound, hop-count, and exponential RIs. Simulations show that RIs can improve performance by one or two orders of magnitude compared to flooding and by up to 100% compared to random forwarding. The paper evaluates the performance of these RIs and discusses trade-offs between them. RIs reduce the number of messages needed to process queries, making them more efficient than traditional methods. The compound RI uses local index summaries, while hop-count and exponential RIs consider the number of hops and exponential decay, respectively. RIs also handle cycles in the network and maintain accuracy despite potential overcounts or undercounts. The paper concludes that RIs, particularly exponential and hop-count RIs, offer significant improvements in search performance for P2P systems while keeping update costs low.Routing Indices (RIs) are introduced to improve the efficiency of content search in peer-to-peer (P2P) systems. Traditional methods either use a costly central index or flood the network with queries, which is inefficient. RIs allow nodes to forward queries to neighbors more likely to have answers, improving performance significantly. Three RI schemes are proposed: compound, hop-count, and exponential RIs. Simulations show that RIs can improve performance by one or two orders of magnitude compared to flooding and by up to 100% compared to random forwarding. The paper evaluates the performance of these RIs and discusses trade-offs between them. RIs reduce the number of messages needed to process queries, making them more efficient than traditional methods. The compound RI uses local index summaries, while hop-count and exponential RIs consider the number of hops and exponential decay, respectively. RIs also handle cycles in the network and maintain accuracy despite potential overcounts or undercounts. The paper concludes that RIs, particularly exponential and hop-count RIs, offer significant improvements in search performance for P2P systems while keeping update costs low.