[Serusers] SER with nathelper & rtprpoxy - how to disable rtpproxy when two phones are behind the SAME NAT

[Greger V. Teigre]

I know there have been several code examples of using avpops to 
accomplish this. Note that fix_nated_register will NOT change the 
contact to the public address, but store received info.  This means the 
ruri may contain a private address when calling t_relay()
g-)

Arek Bekiersz wrote:
> Hi,
>
>
> Not sure if such issue was discussed before.
>
> Is this possible to detect that two phones are behind the same NAT, to
> avoid forcing rtpproxy in SER?
>
>
> This way we let the phones to send media directly to each other in 
> private network behind NAT. Imagine two SIP phones connected to WAN 
> using router with NAT. Both phones are in the same private network.
> Both phones have accounts on SER proxy, that in turn runs nathelper and
> rtpproxy.
>
> Phone_1 <-->
>              NAT  <--> SER,nathelper,rtpproxy
> Phone_2 <-->
>
>
> Normally when we make call between Phone_1 and Phone_2 using SER, RTP
> media will flow from Phone_1 to rtpproxy and back to Phone_2. Well, this
> is basically what we expect from rtpproxy & nathelper :-)
>
> Now somehow we could be able to detect in SER that both phones are
> behind the SAME NAT. When such situation is confirmed, we do not use
> nathelper and rtpproxy. As a result the phones send RTP media directly
> between them in private network, not using (and probably saturating) the
> poor internet link.
>
> I was thinking about:
>
> 1) Standard detection of NAT-ed situation, and then
> 2) comparing source IP of INVITE from Phone_1 with Contact IP stored for
> Phone_2 in "location" table. If they match, both phones MAY be in the
> same private network and we do not use nathelper functions.
>
> Of course it would work only if there is no other NAT before the primary
> NAT (i.e. we do not have the double NAT situation or similar)
>
>
>