23.0403GPPRelease 17Technical realization of the Short Message Service (SMS)TS
According to clause 5, the replying MS knows if:
a) reply path exists; or
b) reply path does not exist.
We then specify that when submitting the reply MO SM, the replying MS should use parameters as follows:
1) TP‑Destination‑Address in SMS‑SUBMIT PDU = originating SME,
2a) If reply path exists:
RP‑Destination‑Address in RP‑MO‑DATA = original SC,
2b) If reply path does not exist:
RP‑Destination‑Address in RS‑MO‑DATA = selected SC or default SC or original SC,
3a) If reply path exists:
after submitting one reply MO SM, the reply path does not exist any more.
In case (2b), it is allowed to use the original SC or the default SC, but then there is no guarantee that the original/default SC shall deliver the reply MO SM. (The original SC may refuse to deliver, if the replying MS is not its subscriber; the default SC may be unable to deliver, if it has no access path to the originating SME.)
Requirement (3a) states that the case (a), reply path exists, holds for one reply MO SM only (per original MT SM).