FAQ-what's the difference between "process-pst" and "process-interface-status" in BFD configuration
Answer:1:The Process-pst is mostly used for FRR linkage, for instance,ip FRR , LDP FRR .etc, if you configure process-pst ,when BFD detect the link has any disconnection it will modify the port status table(it's a understratum table) immediately to port down, and the FRR will convergent shortly because the FRR protocol is always monitoring the port status table .
2:if configuring process-interface-status(PIS) , when BFD detect any abnormality of connection it will make the port "BFD down" (you can see the status through "display interface") , that will make the protocol natural convergence .(for example ospf,BGP)
So we can say the Process-pst is much faster than PIS.But the scenario is different, PST serves for the protocol which based on understratum port status table, and PIS serve for any protocol because it just change the interface protocol status .