CCNx is the reference implementation for a content centric networking (CCN) protocol developed by the Palo Alto Research Center CCNx group. It serves also as reference for our CCN-WSN, a CCNx implementation for wireless sensor networks (WSN). Efficient data aggregation with CCN-WSN is a challenge. In order to collect data from source in the network data sinks have to poll data sources with interests and exclude fields in interests are necessary bloating the interest messages. We solve the problem by introducing three building blocks in CCN-WSN: unicast faces for packet filtering and “link” abstraction, a forwarding service for creating network overlay structures used by applications and an intra-node protocol providing an API for applications to interact with the forwarding service. For evaluation purpose we implement an application using a forwarding service implementing a tree topology to collect data in the WSN.