Issue #359
Updated by Tobias Brunner about 12 years ago
Some NAT implementations seem to assign for each outgoing connection a new Pseudo Port. This Pseudo Port is unknown to the Mediation Server and is therefore not communicated. The mediation Server always assumes that all traffic is channled through the same port. The following example shows the respective NAT translation table of Bob's router (Mediation Server @141.12.72.217@, 141.12.72.217, Alice @84.118.5.87@ 84.118.5.87 and Bob @178.4.168.107@): 178.4.168.107):
<pre>
Index Protocol Local IP Local Port Pseudo IP Pseudo Port Peer IP Peer Port
99 UDP 192.168.61.109 4500 178.4.168.107 4500 141.12.72.217 4500
100 UDP 192.168.61.109 4500 178.4.168.107 4506 192.168.0.20 4500
101 UDP 192.168.61.109 4500 178.4.168.107 4507 192.168.0.19 4500
102 UDP 192.168.61.109 4500 178.4.168.107 4508 84.118.5.87 4500
</pre>
I think a possible fix is to use "fresh" ports for the Alice to Bob connection as at the first usage local and pseudo port are identical. This "fresh" port could then be communicated by the mediation server. If the first time fails a different port can be chosen (even independently on both sides using a predetermind scheme).
<pre>
Index Protocol Local IP Local Port Pseudo IP Pseudo Port Peer IP Peer Port
99 UDP 192.168.61.109 4500 178.4.168.107 4500 141.12.72.217 4500
100 UDP 192.168.61.109 4500 178.4.168.107 4506 192.168.0.20 4500
101 UDP 192.168.61.109 4500 178.4.168.107 4507 192.168.0.19 4500
102 UDP 192.168.61.109 4500 178.4.168.107 4508 84.118.5.87 4500
</pre>
I think a possible fix is to use "fresh" ports for the Alice to Bob connection as at the first usage local and pseudo port are identical. This "fresh" port could then be communicated by the mediation server. If the first time fails a different port can be chosen (even independently on both sides using a predetermind scheme).