1. A method, comprising: forwarding packet flows received at a network node between subscribers of one or more network services and one or more providers of the network services; collecting flow statistics within a data plane of the network node to generate flow statistics updates, the flow statistics being related to each of the packet flows passing through the network node; providing the flow statistics updates to a plurality of statistics engines executing in a control plane of the network node; generating statistics summaries by the statistics engines within the network node, the statistics summaries summarizing the flow statistics on a per subscriber basis, each of the statistics engines being assigned a different subset of the plurality of subscribers to track the flow statistics associated with the different subset and to generate the statistics summaries for the different subset of the plurality of subscribers; and updating the statistics summaries with the flow statistics updates received from the data plane.