Abstract: A method of controlling forwarding of IP data packets through a service network. An IP data packet including an original source port number enters the network through a gateway node. A controller defines a path allocated to a service type through a forwarding node and a service-providing server allocated to the network; allocates an identifier to the service type; provides path-related forwarding rules to the forwarding node based on the identifier; and provides to the gateway node, the service-type identifier and a mapping rule between the identifier and the service type. The gateway node receives the IP data packet and determines which service type the IP data packet refers to; replaces the original source port number with a source port number encoding the identifier of the determined service type based on the mapping rule; and provides the IP data packet to the forwarding node for forwarding on the path.