Things like this can be useful without 100% penetration. Most end-to-end apps support a direct connection as long as either of the endpoints have an open port.

Things like this can be useful without 100% penetration. Most end-to-end apps support a direct connection as long as either of the endpoints have an open port. Endpoints without one can also fall back to relays, but since port mapping is frequently used in gaming, that has higher latency and then users start demanding gateways that support the thing that lowers lag. Then it starts to make it into popular internet gateways. For example, the Comcast consumer gateways generally do support UPnP, which is a miserable protocol with an unnecessary amount of attack surface that should be transitioned to Port Control Protocol as soon as possible, but it demonstrates you can get them to implement things of this nature.