- pfSense UPnP and NAT-PnP documentation: https://www.netgate.com/docs/pfsense/services/configuring-upnp-and-nat-pmp.html
- Wikipedia UPnP article: https://en.wikipedia.org/wiki/Universal_Plug_and_Play
- Wikipedia NAT-PnP documentation: https://en.wikipedia.org/wiki/NAT_Port_Mapping_Protocol