The action is used to identify how a message should be treated based on the realm, application and type. local(1) - Diameter messages that resolve to a route entry with the Local Action set to Local can be satisfied locally, and do not need to be routed to another server. relay(2) - All Diameter messages that fall within this category MUST be routed to a next-hop server, without modifying any non-routing AVPs. proxy(3) - All Diameter messages that fall within this category MUST be routed to a next-hop server. redirect(4) - Diameter messages that fall within this category MUST have the identity of the home Diameter server(s) appended, and returned to the sender of the message.