In one embodiment, a system and method are disclosed for sending a request and receiving a reply. The request contains a network service header including a flow label field and a target index field. The flow label field contains a set of available flow labels. The target index field includes a value indicating a target node. The reply contains information indicating which of the flow labels can be used to route a packet to each of the next hop nodes downstream from the device that sent the reply. This process can be repeated for other nodes on a path, and other paths in a service topology layer. The information determined by this process can be used to perform other necessary functionalities at the service topology layer.