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VOIP Anti-blocking dialler


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We are facing increased endusers’ frustrations with 3G company and Mobile providers blocking the VoIP on their networks. We have changed the default Udp port 5060 to a new number but still not preventing the one way audio. Currently we are using vpn for the clients which addresses the problem for now but on the long run we are looking at anti VoIP blocking solutions.

Any suggestions please ?

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I would assume that all they are looking for is RTP content, which is relatively easy to spot by filtering for UDP packets with a certain header. It does not matter if the content is encrypted or not, the header looks the same.

On the Vodia apps, we could think about changing the RTP packet signature to some random, proprietary format because we control both ends; however this will not work when we use standard SIP devices and software. 

The other interesting avenue could be to loo into RTP header compression (RFC 2508). Maybe the carriers just want to preserve bandwidth and apart from that have nothing against VoIP, and this could be a way to have everyone happy.

Apart from that, there is almost no reason to use the standard port 5060. It just attracts scanners and creates unnecessary traffic.

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19 hours ago, RichardDCG said:

the issue with the mobile carriage is also CGNAT in a lot of cases.  

If the carrier supports IPv6, you can just do that. All you need to do is add an IPv6 record. iOS and I think also Android prefers IPv6 today, so IPv4 and IPv6 can coexist. 

But even with CGNAT it should be working with the Vodia PBX SBC as long as the PBX runs on a public IPv4 address that can be resolved from the handset.

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