[Serusers] STUN and (Media/RTP)Proxy

[Klaus Darilion]

The client will use STUN to detect the type of NAT (coned, symmetric 
...) and the public IP address:port.

If the NAT device can be traversed by means of STUN, then the client 
uses the public IP address and port in the SIP messages (Via: header, 
Contact: header, SDP, ...).

If the NAT device can't traversed by use of STUN (symmetric NAT), the 
client has to behave dumb and does not use the public addresses. Thus, 
it uses its private IP address:port (e.g. 192.168.0.2:5060) in the SIP 
messages.

In ser, you will use nat_uac_test() to test the incoming messages. You 
can test for private IP addresses in the various headers (Via, Contact, 
SDP) and compare the Via: header with the IP-address:port the message is 
coming from. If the client uses STUN and public IP address:port in the 
SIP message, ser can not detect if the client is behind NAT. Thus, ser 
does not NAT traversal - as it should be, because the client das NAT 
traversal itself.

If the nat_uac_test detects that the SIP messages comes from a natted 
client, then you have to use the various functions (force_contact, 
nated_register, force_rtpproxy...) to rewrite the SIP messages.

regards,
klaus

PS: read the README from the nathelper module and the mediaproxy module. 
You have to choose either nathelper-module+rtpproxy or the 
mediaproxy-module+mediaproxy (from ag-projects).


info at beeplove.com wrote:
> If a client come through STUN and behind NAT,
> SER dont need to do anything to handle NAT.
> correct me pls, if I am wrong.
> 
> How ser will figure it out that whether a client is coming through STUN or
> not?
> 
> Thanks,
> Mohammad
> 
> 
> 
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