Dynamic MS-PWs use single-sided signaling procedures with double-sided configuration; a fully qualified FEC must be configured at both endpoints. That is, one T-PE (the source T-PE, ST-PE) of the MS-PW initiates signaling for the MS-PW, while the other end (the terminating T-PE, TT-PE) passively waits for the label mapping message from the far end. This termination end only responds with a label mapping message to set up the opposite direction of the MS-PW when it receives the label mapping from the ST-PE. By default, the router determines which T-PE is the ST-PE (the active T-PE) and which is the TT-PE (the passive T-PE) automatically, based on comparing the SAII with the TAII as unsigned integers. The T-PE with SAII>TAII assumes the active role. However, it is possible to override this behavior using the signaling {master | auto} command under spoke-sdp-fec. If master is selected at a specified T-PE, that T-PE assumes the active role. If a T-PE is at the endpoint of a spoke-SDP that is bound to an VLL SAP and single-sided auto-configuration is used, then that endpoint is always passive. For more information, see Automatic Endpoint Configuration. Therefore, signaling master should only be used when it is known that the far end assumes a passive behavior.