A method of operating a data network may include establishing a data path through the data network between a routing gateway for a subscriber of the data network and a service provider providing a data service. Moreover, the data service may be provided for use at the routing gateway over the data path during a data session. A request may be received from the service provider wherein the request defines a data flow characteristic for the data path between the routing gateway and the service provider providing the data service during the data session. The data flow characteristic may then be transmitted to a node along the data path between the routing gateway and the service provider for enforcement of the data flow characteristic for the data path at the node. More particularly, the data session may be a point-to-point protocol data session. Related methods, data networks, data service providers, routing gateways, and computer program products are also discussed.