below documented somewhere? I tried to google around but did not find anything. There is some scattered information, e.g. this at DB0WA: https://www.afu.rwth-aachen.de/projekte/hamnet/anwendungen/sip-telefonie https://www.afu.rwth-aachen.de/projekte/hamnet/infos-fuer-betreiber/dundi-n… This page also describes a crawler for such nodes and shows a map, but I think this crawler is dead as the map shows information from last year and has not been updated since. That is probably related to the renumbering of the German/Austrian network. (as you know these networks ended up being in the part that was sold) I don't know if the network itself is still actively maintained or if it is just an experiment that is not interesting to its inventers anymore and just keeps running until the servers crash, someone turns them off, or a disruption such as the renumbering occurs.  At least locally for me it works fine, but I use it mainly for calls to one other person who is on the same PBX as I am. Rob