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My ISP is rolling out IPv6 using DS-Lite with PCP enabled. I read the wikipedia page, searched google, and couldn't find answers to some practical questions:

  • On the "client" (ISP subscriber PC), what is responsible for sending PCP MAP requests? The OS, application, or some wrapper? (ie. where should I be looking for "PCP supported"?)
  • Alternatively, the Cisco page mentions a UPnP-PCP Internetworking function, which I gather is basically a translator that sits on the home router, listening for UPnP port mapping requests and forwarding them over PCP to the CGNAT. Would this mean that as long as this is enabled on the router, I only need the application (game server) to support UPnP?
myxal
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1 Answers1

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On the "client" (ISP subscriber PC), what is responsible for sending PCP MAP requests? The OS, application, or some wrapper? (ie. where should I be looking for "PCP supported"?)

Currently, each program sends such requests on its own. There also are standalone tools for sending map requests (e.g. upnpc or natpmpc).

However, I'm not sure if any software supports PCP yet. If you're lucky, you might find support for NAT-PMP (the predecesor to PCP), and your gateway might support NAT-PMP requests. But a large part only support UPnP IGD.

With DS-Lite, I think your home router/gateway is then responsible for translating all received requests (UPnP IGD, NAT-PMP) into PCP and forwarding them to the ISP's upstream router.

Alternatively, the Cisco page mentions a UPnP-PCP Internetworking function, which I gather is basically a translator that sits on the home router, listening for UPnP port mapping requests and forwarding them over PCP to the CGNAT. Would this mean that as long as this is enabled on the router, I only need the application (game server) to support UPnP?

Yes (as long as your router actually supports this feature...)

u1686_grawity
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  • _With DS-Lite, I think your home router/gateway is then responsible for translating all received requests (UPnP IGD, NAT-PMP) into PCP and forwarding them to the ISP's upstream router._ - would be nice if you could provide source. That's the "translation" feature mentioned above, and would be great if I could count on it being present. I don't run my own router, just the ISP one. – myxal Mar 10 '18 at 09:27
  • @myxal Were you able to confirm/test this? I think I'm in the same boat, wondering if there's a way for UPnP port requests to trickle up from user router to CGNat. – AaronLS Dec 29 '21 at 00:03
  • @AaronLS at least on my ISP-supplied Huawei router, the interworking function is not present - with DS Lite, the router reports being not connected over UPnP. – myxal Dec 30 '21 at 16:25
  • I can only open ports manually in the router's web interface, where the section is labeled PCP. The bigger issue is that under my ISP's implementation, I only have a small range of ports available, about 1000 - requests for other ports always fail. PCP allows for the gateway to indicate a free port back to the client , but there's no such mechanism in UPnP-IGD, so with this ISP I'd have map ports manually regardless. You can read more about the function at https://www.rfc-editor.org/rfc/rfc6970.txt – myxal Dec 30 '21 at 16:34