SMF Design Overview
As UPF may not support connections from multiple SMF instances with same Node-Id, UPF-Adapter layer has been introduced.
UPF-Adapter acts like Mux-Demux for PFCP messages between multiple SMF instances and UPF.
SMF sends custom PFCP msg to UPF-Adapter if UPF-Adapter is deployed.
The UPF-Adapter intercepts and modifies certain fields before sending PFCP msg to actual UPF.
Similar handling is done for the response from UPF towards SMF.