Why do you need a Diameter Routing Agent (DRA) in a VoLTE deployment?

Thanks for the interesting article. I was interested in this: "A DRA could also prioritize VoLTE related signaling, over all the various Diameter interfaces. When serving this function, operators can provide a higher quality VoLTE service over other services, particularly when other services load the network." Can I detect whether my Operator has activated such a feature through traces that I can see in Wireshark for instance?