For extensible bit flag data constants, a service-provider vendor can define new values for specified bits. As most bit flag constants are DWORDs, typically a specific number of the lower bits are reserved for common extensions while the remaining upper bits are available for vendor-specific extensions. Common bit flags are assigned from bit zero up, and vendor-specific extensions should be assigned from bit 31 down. This provides maximum flexibility in assigning bit positions to common extensions versus vendor-specific extensions. A vendor is expected to define new values that are natural extensions of the bit flags defined by TSPI.
Extensible data structures have a variably sized field that is reserved for device-specific use. Being variably sized, the service provider decides the amount of information and the interpretation. A vendor that defines a device-specific member is expected to make these natural extensions of the original data structure defined by TSPI.