Mobile entities
If a network cannot interrogate the HLR when delivering a
call, the call is routed to an MSC.
This MSC will interrogate the appropriate HLR and then route the
call to the MSC where the mobile station is located.
The MSC which performs the routing function to the actual
location of the MS is called the Gateway MSC.
The acceptance of an interrogation to an HLR is the decision of
The operator decides which MSCs can act as Gateway MSCs.