SMS-SRI is a MAP (Mobile Application Part) message that stands for Short Message Service – Send Routing Information. It is a message sent by the SMSC (Short Message Service Center) to the HLR (Home Location Register) to request routing information for delivering a short message to a mobile subscriber. The routing information includes the MSC (Mobile Switching Center) or SGSN (Serving GPRS Support Node) address and the IMSI (International Mobile Subscriber Identity) of the subscriber.
Some of the use cases for SMS-SRI are:
• When an SMSC receives a short message from a sender, it needs to know the current location and status of the recipient in order to deliver the message. The SMSC sends an SMS-SRI message to the HLR of the recipient, and the HLR responds with an SMS-SRI-ACK message containing the routing information or an error code.
• When an SMSC receives a delivery report from an MSC or SGSN, it needs to know the address of the sender in order to forward the report. The SMSC sends an SMS-SRI message to the HLR of the sender, and the HLR responds with an SMS-SRI-ACK message containing the routing information or an error code.
• When an SMSC needs to update its routing information cache for a subscriber, it can send an SMS-SRI message to the HLR of the subscriber, and the HLR responds with an SMS-SRI-ACK message containing the routing information or an error code.
