The Shortest Path Source Identifier.
It is the high order 3 bytes for Group Address DA from this
Bridge.
Note that only the 20 bits not including the top 4 bits are
the SPSourceID.
This object is persistent.
It is the high order 3 bytes for Group Address DA from this
Bridge.
Note that only the 20 bits not including the top 4 bits are
the SPSourceID.
This object is persistent.