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Seamless VoIP over 4G with Netcelero

Are you using 4G for broadband and missing some VoIP calls?

Is your business VoIP phone sometimes not ringing? While a lot of time providers put this down to congestion in the local network, that’s often not the case. A lot of the time the issue relates to the UDP port states.

VoIP generally works over UDP, which is a connectionless protocol. Therefore, in order to receive inbound call requests, the VoIP system on site will send “keep alive” packets. In fibre and VDSL, these packets keep the UDP port state open on the on site modem/firewall, thus allowing the central cloud system to be able to “signal” to your phone to ring, so you can then accept the call.

However in 4G networks, the mobile operators use a system called carrier nat. In carrier nat your connection transverses a firewall in the operator’s core network. The states for your traffic are created here, and not back on the modem on site. This means that the state timeouts and other state related settings are beyond your control.

Another issue is that mobile operators often restrict the number of states on a connection to around 500. This restriction is subtle in its effects – if you are the only person on site, then the speeds and responsiveness of the internet will seem fine.

However, if you have a large number of devices on site this is where problems start to appear. Your typical laptop or pc can create up to 400 states itself.  So imagine an office with 5-6 staff members. The effect of the limit of the states is that when you exhaust your states, the operator network will cannibalise your older states, which, you guessed it, are often your UDP VoIP states. This is what leads to intermittent missed calls and no business wants to miss a call.

By deploying an i-ctrl by Netcelero on site, to handle your VoIP calls, the states for the VoIP system get created on the Netcelero public IP and NOT in the carrier core network. This means that you are not limited to 500 states, you have the full range typically available to a site on fibre or VDSL of around 60,000. No more missed calls!

It is important to bear in mind that 4G or 5G data networks are not circuit switched, like ISDN or PSTN lines – so there is no guarantee or SLA on call quality. The use of an i-ctrl can assist where the states is the issue, it can not make data network perform like circuited switched networks.