Most existing routing protocols designed for WSNs assume that links are symmetric, which is in contradiction with what is observed in the field. Indeed, many links in real-world WSNs are asymmetric. Asymmetric links can dramatically decrease the performance of routing algorithms not designed to cope with them. Quite naturally, most existing routing protocol implementations prune the asymmetric links to only use the symmetric ones. In our experience, asymmetric links are a valuable asset to improve network connectivity, capacity and overall performance. We therefore introduce AsymRP (Asymmetric Convergecast Routing Protocol), a new routing protocol for collecting data in WSNs. AsymRP, a convergecast routing protocol, assumes 2-hop neighborhood knowledge and uses implicit and explicit acknowledgment. It takes advantage of asymmetric links to increase delivery ratio while lowering hop count and packet replication.