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Unread 08-18-2007, 03:32 PM   #12
hust
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Default my understanding about "Symmetric NAT Handling" field

My understanding about “Symmetric NAT Handling" field on the Member Details page again.

1.If you set “Symmetric NAT Handling" to “yes”, it enables Voxalot NAT handling built-in logic.

In this case, Voxalot servers can help you to solve all traversing NAT issues. You need not consider how to configure stun server or outbound proxy server(TURN) option in your ATA if your ATA is behind NAT(router).

1A. If your ATA is sitting on public IP address

Voxalot special SIP proxy server can detect your ATA is sitting on public IP address ,so Voxalot attempt to to optimize the voice route(initiate the RE_INVITEs).If your VSP supports RE_INVITEs, you will get optimization voice route(path),point to point, bypassing Voxalot RTP proxy server . If your VSP does not support RE_INVITEs, you will get triangle round-trip voice path.i.e,your ATA sends RTP voice packets direct to your VSP, the RTP voice packets from your VSP come in via Voxalot RTP proxy server.

1B. If your ATA is behind cone NAT(includes Full cone, Restricted cone, Port restricted cone)

Voxalot special SIP proxy server can detect your ATA is behind NAT, and modify your SIP(SDP) to help your RTP voice packets to traverse your cone NAT, but your all RTP voice packets should pass Voxalot RTP proxy server(RTP relay) , you have no chance to bypass it. So, hardly can you optimize voice path to p2p.

Edit: The only exception is that you have configured right stun server in your ATA though you need not do it, and you will get optimization voice path similar with "1A".

1C. If your ATA is behind symmetric NAT

Voxalot special SIP proxy server can detect your ATA is behind NAT, and modify your SIP(SDP) to help your RTP voice packets to traverse symmetric NAT, but your all RTP voice packets should pass Voxalot RTP proxy server(RTP relay) , you have no chance to bypass it. So, you have no way to optimize voice path to p2p.

In this case, you need not consider “Optimize audio path” is “yes” or “no” on the Voice Service Provider page. Regardless you set it “yes” or “no”, voice path has the same effect.


2. If you set “Symmetric NAT Handling" to “no”, it disables Voxalot NAT handling built-in logic.

In this case, you should solve traversing NAT issue by yourself . You need configure stun server or outbound proxy server(TURN) option in your ATA if your ATA is behind NAT(router)

2A. If your ATA is sitting on public IP address

a.If “Optimize audio path” is “yes” on the Voice Service Provider page.
Voxalot attempt to optimize the voice route(initiate the RE_INVITEs).If your VSP supports RE_INVITEs, you will get optimization voice route(path),point to point, bypassing Voxalot RTP proxy server . If your VSP does not support RE_INVITEs, you will get triangle round-trip voice path.i.e,your ATA sends RTP voice packets direct to your VSP, the RTP voice packets from your VSP come in via Voxalot RTP proxy server.

b.If “Optimize audio path” is “no” on the Voice Service Provider page.

Your all RTP voice packets should pass Voxalot RTP proxy server, you lose the chance to bypass it, so, you have no way to optimize voice path to p2p.

2B. If your ATA is behind cone NAT(includes Full cone, Restricted cone, Port restricted cone)
At first, you should configure stun server option in your ATA(e.g. stun.xten.com) to traverse NAT by yourself.

a. If “Optimize audio path” is “yes” on the Voice Service Provider page.

Voxalot attempt to optimize the voice route(initiate the RE_INVITEs).If your VSP supports RE_INVITEs, you will get optimization voice route(path),point to point, bypassing Voxalot RTP proxy server . If your VSP does not support RE_INVITEs, you will get triangle round-trip voice path.i.e,your ATA sends RTP voice packets direct to your VSP, the RTP voice packets from your VSP come in via Voxalot RTP proxy server.

b. If “Optimize audio path” is “no” on the Voice Service Provider page.

your all RTP voice packets should pass Voxalot RTP proxy server, you lose the chance to bypass it, so, you have no way to optimize voice path to p2p.

2C. If your ATA is behind symmetric NAT
At first , you should configure outbound proxy server(TURN) option in your ATA to traverse symmetric NAT. your sip signalling and RTP voice packets will pass this outbound proxy server(TURN) then to Voxalot servers.

These below a and b are my estimation.

a. If “Optimize audio path” is “yes” on the Voice Service Provider page

Voxalot attempt to optimize the voice route(initiate the RE_INVITEs to this outbound proxt server(TURN) and your VSP).then……….
Please help me to finish here…

b. If “Optimize audio path” is “no” on the Voice Service Provider page

your all RTP voice packets should pass outbound proxy server(TURN) and Voxalot RTP proxy server, you have no chance to bypass its, so, you have no way to optimize voice path to p2p. Unfortunately, your RTP voice packets must pass two proxy servers.

I think if your ATA is behind symmetric NAT, the best way is to set “Symmetric NAT Handling" to “yes” to avoid such troubles.




I have studied some from post written by member v164.

Welcome anyone to correct this post above.

Last edited by hust; 08-20-2007 at 05:34 PM. Reason: 1.correct spelling 2.edit
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