This attribute specifies the Internet Protocol (IP) Address of the
Mobile Telephone Exchange (MTX) that is permitted to set up
MTX InterWorking Function (IWF) data calls using this
TdmaIwfCallServer. This address must be specified in order for this
TdmaIwfCallServer to provide service.
If call setups are attempted from an MSC which does not have this
address, those calls are rejected. The callsRequested statistic of this
TdmaIwfCallServer is incremented and appropriate call failure logs
are generated at the MSC.