Most of the existing routing protocol designed for WSNs assume that links are symmetric which is in contradiction to the reality of these networks. Indeed, asymmetric links cannot be ignored in WSNs as they can be predominant. The apparition of asymmetric links can dramatically decrease routing protocols that are not designed to support them by decreasing the delivery ratio and increasing the duplicated packet received at the destination. Obviously, most of the existing routing protocols prune the asymmetric links and only maintain the symmetric ones. From our point of view, the asymmetric links have to be considered as they can be effective in the network connectivity insurance. Moreover, they open new opportunities to improve the performance of routing protocols. From this perspective and in order to take benefit from asymmetric links, we propose a routing protocol for data collection in WSNs called AsymRP (Asymmetric Routing Protocol). AsymRP is a convergecast routing protocol which is based on a 2-hop neighbor knowledge combined with implicit and explicit source routing acknowledgment. Our proposal takes advantage of asymmetric links, enables the network to achieve higher delivery ratio while reducing significantly the number of duplicated packets and hop counts. Our simulation results show that our proposal AsymRP can significantly outperform traditional routing protocols in the presence of asymmetric links in the network.