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The Graveyard - Products No Longer Supported => Routers / COVR => DIR-655 => Topic started by: dulceangustia on June 12, 2009, 02:02:04 AM

Title: [DIR-635] SIP ALG changes RTP port in m= header of SDP file
Post by: dulceangustia on June 12, 2009, 02:02:04 AM

Hi,

First of all, I'd like to apologize because the product my question is about is a D-Link DIR-635, not DIR-655 but, as I've not found any specific forum for my product as it is discontinued and its replacement has been decided to be DIR-655 I thought that this was the better place to post my question. If I'm wrong, please, move the thread to the corresponding forum. Thanks.

This is my problem:

I'm experiencing a weird issue while testing a VoIP (SIP/RTP) session handover between two private networks (two DIR-635 gateways). It seems to be related to the SIP support of the Application Level Gateway included in these devices and I would like to know if you could help to understand what is happening here.

I'm using a Debian Lenny box A with a public IP and a Debian Lenny box B within a private wifi LAN 1 that, while in a VoIP session with the box A attaches to the wifi LAN 2 and issues a re-INVITE SIP message to the box A. What I get is that SIP ALG of DIR-635 changes the RTP port of the m= header in the SDP file sent from the box B (which issues the re-INVITE to box A, once B has attached to the LAN 2). While the IP switching from private to public address (this last being the gateway one) is properly performed by the ALG, I don't know why it also changes the RTP port. So, box B expects RTP packets to reach one port and box A sends to a different one, while the ALG doesn't redirect properly the corresponding packets. I've tried with different NAT endpoint configurations and all behave the same way.

I'm using PJSUA softphone (pjproject 1.2) to make these tests on both boxes. It uses RTP/RTCP ports from 4000 to 4008 and SIP port 5060 by default, which I'm using. The ALG changes the 4000 port from the original SDP file in the re-INVITE message to a random port [10000-53000] in my tests.


As said before, I would like to know if you could tell me how SIP ALG manages the SDP file in this case and how could I work around this issue.


Thanks for your time and best regards,
Javi

Title: Re: [DIR-635] SIP ALG changes RTP port in m= header of SDP file
Post by: dulceangustia on June 15, 2009, 02:38:57 AM

Any help on this?

Regards.

Title: Re: [DIR-635] SIP ALG changes RTP port in m= header of SDP file
Post by: Demonized on June 15, 2009, 02:41:46 AM

Kicking the post after 30 minutes is not very elegant. Most people sleep at the times you post...

I would suggest also posting on a VOIP dedicated forum.

Title: Re: [DIR-635] SIP ALG changes RTP port in m= header of SDP file
Post by: dulceangustia on June 15, 2009, 02:47:18 AM

Check the first post date, please.

Anyway, the D-LINK VoIP forum seems not to be the right place to post this issue as it is dedicated to specific VoIP products, and my problem is related to DIR-635's ALG.

Regards.