For Payment Facilitator integrations, the Payment Facilitator is boarded as a unique MID on Portico.  The sub-merchant  POS sends the request to the Payment Facilitator, which passes it to Portico for authorization. 

Payment Facilitator integrations are supported on the GSAP-NA Authorization Host.

During transaction processing, the sub-merchant POS sends the request to the Payment Facilitator, which passes it to Portico for processing.  Portico sends the request to the front end host and passes the response back to the Payment Facilitator, which passes it back to the sub-merchant's POS.