Apparently some people within the IETF have started a new working group called 'BEHAVE'. It is about the behaviour of NAT devices on the internet, and their inconsistent and incompatible behaviour. The working group aims to give guidelines to ipmlementors, in order to assure interoperability with new applications such as VoIP and peer-to-peer protocols, as well as multicast and others.
Certainly a topic that is in in the main focus of my interest, so I decided this is the right point in time to start participation in the IETF.
For more information about behave, see the mailinglist.