The value of vRtrPimNgDataMtCGrpSrcJoinTimer indicates the time
interval before the Provider Edge (PE) router connected to the
source switches to the Data Multicast Distribution Tree (MDT) group.
After providing sufficient time for all PE's to join the data MDT the
transmitting PE switches the given multicast stream to the Data MDT.
The PE router connected to the source then starts encapsulating
traffic using the Data MDT group.