Editing Universal Plug and Play (section)

==NAT traversal==
One solution for [[NAT traversal]], called the [[Internet Gateway Device Protocol|Internet Gateway Device Control Protocol]] (UPnP IGD Protocol), is implemented via UPnP. Many [[router (computing)|router]]s and [[firewall (computing)|firewall]]s expose themselves as Internet Gateway Devices, allowing any local UPnP control point to perform a variety of actions, including retrieving the external IP address of the device, enumerating existing port mappings, and adding or removing port mappings. By adding a port mapping, a UPnP controller behind the IGD can enable traversal of the IGD from an external address to an internal client.

There are numerous compatibility issues due the different interpretations of the very large actually backward compatible IGDv1 and IGDv2 specifications. One of them is the UPnP IGD client integrated with current Microsoft Windows and Xbox systems with certified IGDv2 routers. The compatibility issue still exist since the introduced of the IGDv1 client in Windows XP in 2001, and a IGDv2 router without a workaround that makes router port mapping impossible.<ref>{{Cite web |title=Detect FDSSDP as a microsoft client · miniupnp/miniupnp@8381867 |url=https://github.com/miniupnp/miniupnp/commit/8381867faf82f3d779f797e59582b3c76a827ecd |access-date=2023-09-18 |website=GitHub |language=en}}</ref>

If UPnP is only used to control router port mappings and pinholes, there are alternative, newer much simpler and lightweight protocols such as the [[Port Control Protocol|PCP]] and the [[NAT Port Mapping Protocol|NAT-PMP]], both of which have been standardized as RFCs by the IETF. These alternatives are not yet known to have compatibility issues between different clients and servers, but adoption is still low. For consumer routers, only [[AVM GmbH|AVM]] and the open-source router software projects [[OpenWrt]], [[OPNsense]], and [[pfSense]] are currently known to support [[Port Control Protocol|PCP]] as an alternative to UPnP. [[AVM GmbH|AVM]]'s [[Fritz!Box]] UPnP IGDv2 and PCP implementation has been very buggy since its introduction. In many cases it does not work.<ref>[https://pastbin.net/avmticket 12 Fehler in der AVM UPnP IGD- und PCP-Implementation (aller FritzBoxen)].</ref><ref>{{Cite web |date=2022-04-12 |title=UPnP not working with my FRITX!Box |url=https://forum.syncthing.net/t/upnp-not-working-with-my-fritx-box/18281/16 |access-date=2023-09-18 |website=Syncthing Community Forum |language=en}}</ref><ref>{{Cite web |title=UPNP_GetValidIGD returns Temporary IPv6 Address, causing UPNP_AddPinHole to fail with 606 · Issue #600 · miniupnp/miniupnp |url=https://github.com/miniupnp/miniupnp/issues/600 |access-date=2023-09-18 |website=GitHub |language=en}}</ref><ref>{{Cite web |title=upnpc shows wrong duration for port forward longer than 120 seconds · Issue #222 · miniupnp/miniupnp |url=https://github.com/miniupnp/miniupnp/issues/222 |access-date=2023-09-18 |website=GitHub |language=en}}</ref><ref>{{Cite web |title=miniupnp.tuxfamily.org :: View topic - Setting up portforward doesn't work |url=https://miniupnp.tuxfamily.org/forum/viewtopic.php?t=867 |access-date=2023-09-18 |website=miniupnp.tuxfamily.org}}</ref>