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Andy Yang | 11 Feb 2006 04:24
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TURN help !!!

Hi All,

I am new to this board but your help will be greatly appreciated.

I have a doubt regarding the two TURN clients both behind a symmetric  
NAT can communicate with each other using a TURN server. Please help me

Scenario:

A-----NAT 1------TURN SERVER-----NAT 2-----B

A: (a.a.a.a:1234)
B: (b.b.b.b:1234)
TURN Server: (x.x.x.x:3478)
NAT 1 and NAT 2 are both symmetric.

My understanding:
1. A, B will both send ALLOCATE to TURN server (x.x.x.x:3478), and  
get response. Suppose A is allocated x.x.x.x:11111, B is allocated  
x.x.x.x:22222.
2. A send SEND request to TURN server (x.x.x.x:3478), set  
REMOE_ADDRESS(b.b.b.b:1234); TURN server will use A's allocated  
address (x.x.x.x:1111) to send DATA to B (b.b.b.b.b:1234). It cannot  
go through NAT 2.
3. B send SEND request to TURN server(x.x.x.x:3478), set  
REMOTE_ADDRESS(a.a.a.a:1234); TURN server will use B's allocated  
address (x.x.x.x:2222) to send DATA to A (a.a.a.a:1234). It cannot go  
through NAT 1, either.

Is there anything wrong  here?
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Justin Uberti | 11 Feb 2006 04:52
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Re: TURN help !!!

Andy,

In the simplest case, when A wants to send data to B, it will make a 
TURN send request to send to B's TURN address x.x.x.x:22222. A's TURN 
server will send this data from x.x.x.x:11111 to B at x.x.x.x:22222, 
which will be forwarded to B at b.b.b.b:1234.

In the real world, TURN will typically be used with ICE, where A will 
send to B's TURN address, B's STUN-derived address, and b.b.b.b:1234, 
and will use the best address that works.

Hope this helps,
--justin

ayang <at> apple.com wrote:

> Hi All,
>
> I am new to this board but your help will be greatly appreciated.
>
> I have a doubt regarding the two TURN clients both behind a symmetric  
> NAT can communicate with each other using a TURN server. Please help me
>
> Scenario:
>
> A-----NAT 1------TURN SERVER-----NAT 2-----B
>
> A: (a.a.a.a:1234)
> B: (b.b.b.b:1234)
> TURN Server: (x.x.x.x:3478)
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