When a Data packet arrives, an NDN router finds the matching PIT entry and forwards the data to all down-stream interfaces listed in that PIT entry. It then removes that PIT entry, and caches the Data in the Content Store. Data packets always take the reverse path of Interests, and, in the absence of packet losses, one Interest packet results in one Data packet on each link, providing flow balance. To fetch large content objects that comprise multiple packets, Interests provide a similar role in controlling traffic flow as TCP ACKs in today's Internet: a fine-grained feedback loop controlled by the consumer of the data.