In ISO message, what's the use of STAN and RRN?
In ISO message, what's the use of STAN and RRN fields? Also, who will generate these values while sending ISO messages?
Answer
STAN - usually generated by your network interface to make it unique per online message request.
RRN - is the transaction related reference and can be generated by POS system, Integrator environment or the generation can be done behind the authorisation interface by the acquired/issuer systems. Depending of RRN generation side the responsibility to make it unique (or keep same for some cases) can be at the client side or at the authorisation institutions side.
Both values required to trace the transaction flows and used for chained transactions like Reversal, Top-Up, Completion, etc.
The difference is the layer of the transaction identifier. STAN is the network layer and message reference. RRN is the customer's integration layer and transaction reference.
They can be mixed in practice, depending of transaction processing requirements. For sample STAN can be a part of RRN.