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4 Replies Last post: Sep 18, 2008 9:06 AM by acruz  
 
acruz
5 posts since
Sep 17, 2008

Sep 17, 2008 11:30 PM

Far-End NAT Traversal Deployment

Hi everybody I'm a newbie in opensbc but I have been searching at the discussions before to post this question. I want to deploy the opensbc in the following scenario:

UA1
NAT

INTERNET
opensbc
INTERNET
softswitch
 

UA2
NAT PSTN-gateway

1. UA1 and UA2 are behind a NAT.
2. opensbc has a public IP address.
3. softswitch has a public IP address.
4. PSTN-gateway has a public IP address.

The behaivor we want to have is the following.

A) All the calls from the nated UAs should be proxied for signaling-only to the softswitch.
B) The contact attribute (c= IN IP4 X.X.X.X) and the media attribute (m=audio <UDP-PORT> RTP/AVP X X X) at the SDP information from the UAs should be forwarded/relayed to the softswitch with the real IP address and the real UDP-PORT so the RTP could be established directly between UA1 and UA2, or between any UA and the PSTN-gateway in order to avoid the double bandwith consumption at the opensbc location.

Is possible to deploy this kind of scenario with opensbc?

Regards
Tags: nat_traversal
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ehernaez
67 posts since
Aug 28, 2007
1. Sep 18, 2008 12:12 AM in response to: acruz
Re: Far-End NAT Traversal Deployment

Your desired senarios are not currently possible with OSBC. The reason is that they will not work. Certain types of NAT will not allow media in if it originates from an IP address other than the one to which a binding has been established (ie. the OSBC public IP address in your example). Unfortunately, proxying media
through OSBC is the price you pay for reliable NAT traversal.

However, your desired scenario can be achieved by using STUN on the UAs. If OSBC detects a public IP address in the CONTACT address, it will not proxy media, and will simply pass along the public IP address to the other side.

 
acruz
5 posts since
Sep 17, 2008
2. Sep 18, 2008 12:18 AM in response to: ehernaez
Re: Far-End NAT Traversal Deployment

Thanks for you reply. Are you planning to support something like this in the future?

Regards

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ehernaez
67 posts since
Aug 28, 2007
3. Sep 18, 2008 12:25 AM in response to: acruz
Re: Far-End NAT Traversal Deployment
Sorry, we have no plans to implement this. Is there a reason why you do not want to use STUN on the UAs? It would accomplish your objectives 100%. OSBC would proxy the signalling, but not the media.
 
acruz
5 posts since
Sep 17, 2008
4. Sep 18, 2008 9:06 AM in response to: ehernaez
Re: Far-End NAT Traversal Deployment

Not all the UAs support/include STUN features and sometimes even they have the STUN feature, the SIP protocol+STUN doesn't work depending of the type of firewall.

There are commercial solutions like NEXTONE, MERA or SANSAY that support this kind of deployment without using STUN it was because I was wondering if OPENSBC could do the same.

Regards

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