Editing Short Message Peer-to-Peer (section)

=== Message ID in SMPP 3.3 SMSC Delivery Receipts ===

The only way to pass delivery receipts in SMPP 3.3 is to put information in a text form to the <code>short_message</code> field; however, the format of the text is described in Appendix B of SMPP 3.4, although SMPP 3.4 may (and should) use <code>receipted_message_id</code> and <code>message_state</code> TLVs for the purpose. While SMPP 3.3 states that Message ID is a C-Octet String (Hex) of up to 8 characters (plus terminating '\0'), the SMPP 3.4 specification states that the id field in the Delivery Receipt Format is a C-Octet String (Decimal) of up to 10 characters. This splits SMPP implementations to 2 groups:

* Implementations using the decimal representation of an integer Message Id in the id field of the Delivery Receipt body and the hexadecimal representation of an integer Message Id in <code>message_id</code> and <code>receipted_message_id</code> fields
* Implementations using the same hexadecimal number (or even the same arbitrary string) both in <code>message_id</code> parameter and in the id field of the Delivery Receipt body

The SMPP 3.4 specification does however state that the delivery receipt format is SMSC vendor specific, and therefore the format included in the specification is merely one possibility. As noted above, when using SMPP 3.4 <code>receipted_message_id</code> and <code>message_state</code> TLVs should be used to convey the outcome of a message.