[asterisk-dev] SIP/NAT handling again (with patch)

[Klaus Darilion]

Luigi Rizzo wrote:
> In my struggling with SIP-behind-NAT issues, i found out that asterisk
> is not making use of useful information coming from the remote party,
> namely the 'received=' and 'rport=' fields in the Via: header,
> which are used by the remote party to report the address and port
> where they see us.
> Note that this information is exceedingly useful in evironments
> where you have symmetric NAT, and STUN and other nat traversal
> techniques are useless because the external mapping depends on the
> 4-tuple src-ip,src-port,dst-ip,dst-port and not just on the src-ip,src-port.

Extracting the rport and received parameter from the received response 
indeed enables you to signal the proper public socket in the SIP 
requests. But how do you handle RTP NAT traversal when behind a 
symmetric NAT?

regards
klaus