An intermediate node obtains a lead packet of a plurality of packets in a session having a unique session identifier, modifies the lead packet to identify at least the intermediate node and also to identify source and destination port numbers assigned by the intermediate node for a possible forward association, and then forwards the lead packet toward the destination node though an intermediate node electronic output interface to the IP network. The intermediate node also may receive, through an intermediate node electronic input interface in communication with the IP network, a backward message from a next node having a next node identifier. Both the intermediate node and the next node form an association between the intermediate node identifier, the next node identifier, and the source and destination port numbers assigned by the intermediate node. This association is part of a forward association for the intermediate node and is part of a return associate for the next node.