This advisor assumes that your network supports differentiated service(DiffServ)-aware routers. DiffServ-aware routers must be able to prioritize packets, based on the codepoint marking in their IP header. If your network does not use DiffServ-aware routers, you can still send the IP packets. The connection will still be made, but your traffic might not receive the priority you intend.
After the applications' IP packets leave your network, you will not be able to control any router along the traffic's path. If the traffic passes through a router without differentiated service, your traffic will not be given priority at that particular router. Check with your Internet service provider (ISP), partner companies, or other necessary groups to see what capabilities they offer.
Does your network have DiffServ-aware routers?