C.4.4 SMS Reply and Notification Handling

The SMS Gateway Server maintains a historical record of each SMS message relayed through its SMPP relays. The need to use historical data arises from the fact that when submitting an email message to SMS it is generally not possible to convert the email address of the message’s originator to an SMS source address. Since any SMS replies and notifications will be directed to this SMS source address, a problem arises. This is resolved by using automatically generated, unique SMS source addresses in relayed messages. The remote SMSCs are then configured to route these SMS source addresses back to the Gateway SMPP server.

The historical data is represented as an in-memory hash table of message IDs and generated, unique SMS source addresses. This data along with the associated email origination data are also stored on disk. The disk based storage is a series of files, each file representing HASH_FILE_ROLLOVER_PERIOD seconds of transactions (the default is 30 minutes). Each file is retained for RECORD_LIFETIME seconds (the default is 3 days). See theSun Java Communications Suite 5 Deployment Planning Guide for a discussion of the in-memory and on-disk resource requirements of the historical data.

Each record has three components:

• Email origination data (such as, envelope From: and To: addresses). This data is supplied by the MTA SMS channel when it submits a message.

• The unique SMS source address generated by the SMPP relay and inserted into the relayed SMS message.

• The resulting receipted message ID returned by the remote SMSC’s SMPP server when it accepts a submission.

C.4.4.1 Routing Process for SMS Replies

The Gateway SMPP relays and servers use historical records to handle SMS replies, notifications and mobile originated messages. When an SMS message is presented to the SMPP relay or server, the following routing process is followed:

1. The SMS destination address is compared against the historical record to see if there is a matching, unique SMS source address that the SMPP relay previously generated. If a match is found, see Step 6. .

2. If there is no match, but the message is an SMS notification (SMPP DELIVER_SM PDU), then the receipted message ID, if present, is compared against the historical record. If a match is found, go to Step 8. [The SMS Gateway Server actually allows these to be presented to either the SMPP relay or SMPP server.]

3. If there is no match, then the destination SMS address is compared against the SELECT_RE option expressions for each configured gateway profile. If a match is found, then go to Step 9.

4. If there is no match and the SMS message was presented to the Gateway SMPP relay, then the message is relayed to the remote SMPP server.

5. If there is no match and the SMS message was presented to the Gateway SMPP server, then the message is determined to be an invalid message and an error response is returned in the SMPP response PDU. For email to SMS, a Non Delivery Notification (NDN) is eventually generated.

6. If a matching unique SMS source address was found, then the SMS message is further inspected to see if it is a reply or a notification message. To be a notification message it must be a SUBMIT_SM PDU with a receipted message ID. Otherwise, it is considered to be a reply.

7. If it is a reply then the SMS message is converted to an email message using the origination email information from the historical record.

8. If it is a notification, then the SMS message is converted to an email Delivery Status Notification (DSN) as per RFC 1892-1894. Note that the ESMTP NOTIFY flags (RFC 1891) of the original email message will be honored (For example, if the SMS message is a “success” DSN but the original email message requested only “failure” notifications, then the SMS notification will be discarded).

9. If the destination SMS address matches a SELECT_RE option in a configured gateway profile, then the SMS message is treated as a mobile originated message and converted back to email message as per the PARSE_RE_n rules for that gateway profile. If the conversion fails, then the SMS message is invalid and an error response is returned.