A running VTS system contains one "root" system object and multiple application "root" objects. The Binary GUID field is used to discriminate between these root objects and allow RPC Manager to determine a starting scope in which to search for a target RPC subroutine.
The Binary GUID for an application root is the same GUID as used in the GDI.WIF file to uniquely identify an application's code objects within the distributed domain. That Binary GUID is the same for all instances of the same application.
RPCs directed at the system root level carry an all-zero Binary GUID. An all-zero Binary GUID is also used on control messages.