STUN - Simple Traversal of UDP Through NATs

• STUN protocol : RFC3489 March 2003 standard, IETF February 2005 memo
• General description of various P2P connection mechanisms
• NAT types
• NAT traversal using hole punching
• Symmetric/symmetric NAT traversal
• different traversal techniques : comparison, IAB considerations

The STUN client protocol implementation uses its own UDP socket layer to communicate with one or more servers. The discovery process begins with determining of free UDP socket starting at port number 36000 and continuing downwards. The discovery itself is currently implemented using five-step procedure described in March 2003 standard. The whole process does not last more than 10 seconds ( actually, full discovery in wost, symmetric/symmetric case, can take as long as 105 seconds) and is able to discover information necessary for performing UDP NAT traversal using hole punching : accessibility of public and private addresses and the type of most restrictive NAT between the client and the STUN server.

• apINetStateService
• apINetStateCallback

• Vovida server
• Vovida derived client & server
• JSTUN client & server, in Java

• Vovida 0.96 : stun.fwdnet.net, stun.fwd.org, stun01.sipphone.com, stun.softjoys.com, stun.voipbuster.com, stun.voxgratia.org, stun.xten.com, stun.noc.ams-ix.net