[SR-Users] How ICE works with private IPs as candidates?

[Richard Fuchs]

On 04/21/2017 04:46 AM, Denys Pozniak wrote:
> Hello!
>
> I have next topology: ISP->Kamailio + Rtpengine->WebRTC
> Sometimes I receive from Browser side SDP like below with private IPs 
> in ICE candidates.
>
>   * Please explain why it happens?
>   * How ICE finds a pair? I think Rtpengine obtains packet from
>     Browser and somehow matches with peer (as it can't reach Browser
>     via private IP)
>
ICE candidate collection is done entirely on the client side, i.e. in 
the browser. If your browser fails to obtain public address ICE 
candidates, it's a problem with the browser script.

ICE should still be able to find a working candidate pair though, 
because once the opposite direction SDP is seen by the browser (which 
should contain public address ICE candidates from the other client or 
rtpengine), the browser will start sending checks to these candidates 
and the other side will then see the NAT'd address and use this to run 
checks. ICE completion would be delayed until after the answer/200 is 
seen, but it should still complete.

Cheers
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