I have been installing 3CX for a couple years now for small to midsize companies with 15-20 Yealink T42S and T46S phones -- all of them on SIP.US trunks. About half of them have SBC's (the ones who have complained about choppy/ghost calls). We have a client using vonage business and about ~40 Cisco SPA504G VoIP phones (and some SPA301 and 303's), and they want us to upgrade them to 3CX (yay!). My question is, how have they been getting away with good call quality for years (granted they do have times where a call might drop or one-way audio, but it is very RARE, so rare that when I ask them the last time a call was bad they cannot remember) when they're all STUN and on the same network and don't have anything like the SBC in place?
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We have only 6 Yealink phones in our office with a SBC. I went to upgrade our 3CX to ver 16 last week but before doing that, I changed them all to STUN to make the upgrade easier (since SBC provisioning process has changed a little recently). Within a day everyone was screaming at me to fix it! Calls would come in, and we couldn't hear the person. Put the phones back on the SBC and will do the upgrade some time in the future. Thanks again for your time and input.
In all seriousness it's certainly doable but it's an administrative headache if you do it by the book, and if you don't and just get lucky because the firewall plays nice you are at the mercy of a phone firmware update or firewall update and then it all falls down. SBC just works.
