Based on its name and PortIndex syntax, this value identifies the specific port number of the synchronous data circuit (SDC) interface this table row describes; the source MIB provides no description text for this object. Admins would use it alongside the position and circuit indexes to fully identify a specific physical SDC port when reviewing its speed, gender, or lead-state data. As an illustrative example, a value of 1 would identify port 1 at the given chassis position as the specific SDC interface described by this row.