Reply to post: It depends

BT pushes ahead with plans to switch off telephone network

Christian Berger

It depends

First of all you already have that problem with regular ISDN, there the solution is simply to have a local battery backup... which your PBX will need anyhow.

If you still get a network connection depends on the way it's handled. For example classical ADSL tends to come directly from the old "switching office" where you have battery backup, so it should work fine. VDSL, particularly when done at the "curb" would need decentralized battery backups which may work. It won't work for vectoring as those boxes need _insane_ amount of power. If you have a dedicated fibre to your "switching office" to your home, it's likely to work. DOCSIS has many amplifiers and media converters, some of which are powered by the "groundstation" some are somewhere hidden inside your home.

The good thing about VoIP from a reliability aspect is that you just need any kind of decent Internet access. At work we've had many companies using even things like LTE when their wire based connection broke down. For a competent administrator it's easy to patch together a perfectly acceptable emergency solutions. This is far harder with ISDN as if your provider's ISDN switch goes down, you're toast and there's nothing you can do about it. ISDN equipment used to be highly reliably, however now 30-40 years into the lifetime of the equipment you find more and more failures, but no more spare parts.

So in short it's hard to say if VoIP will be more or less reliable given a certain situation. The main problem on current networks is that operators are trying out every new feature they can find. The result is that things like DTMF won't work, because one operator wants to do them as telephony-events, while the other one wants to do them inband (the saner alternative), and they somehow mess up signalling so both sides have different opinions on what's been negotiated.

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