7.12 IST of non-CAMEL implementation

23.1193GPPGateway Location Register (GLR)Release 17Stage 2TS

If the GLR supports IST, when the GLR receives an Update Location request that indicates that the MSC/VLR supports IST, it relays the indication to the HLR. If not, the GLR may ignore the indication. When the GLR receives an IST Alert Request from the MSC, it relays the message to the HLR. The HLR sends an IST Alert Response to the GLR, and then the GLR relays the message to the MSC.

When the IM-MSC receives an IST Command Request from the HLR, it retrieves the location information, i.e., MSC Number, from the GLR and sends the message to the MSC. Then the IM-MSC receives the response from the MSC and sends the response to the HLR.