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Re: IP telephony
On dinsdag, sep 16, 2003, at 23:38 Europe/Amsterdam, Christopher Bird wrote:
There has been much buzz of late about using IP telephony solutions in place of the more common analog based solutions.
Traditional telephony has very high reliability (many years without lossFirst of all, I don't use IP telephony myself (yet) so the usual disclaimers and more apply.
The telephony world may claim very high reliability, but they don't deliver when you need it the most. During 9/11 the phone network had huge problems. Not so much because lines and equipment were destroyed, but simply because too many people picked up the phone at the same time. The same thing happened at a smaller scale during last months blackouts.
The individual parts in an IP network are probably less reliable than the individual parts in a POTS network, so you're likely to see more outages. On the other hand, IP networks use a distributed model, while POTS networks use a centralized model. So when something fails in an IP network the consequences are usually not too serious (given good network design of course) while with POTS you're usually in trouble.
Note that you need to make the distinction between IP-only calls and calls that originate or terminate in the public POTS network. For the former, you should be able to reach reliability levels that are no worse than that of good PABX equipment, as long as you don't use the public internet as part of your IP path. For the latter, you're not going to improve upon a PABX. You may be able to achieve good reliability for outgoing calls by building in huge amounts of (geographic) redundancy in the POTS gateways, but I don't think this is possible for incoming calls.
If you want to make calls over the public internet you're not going to be very reliable. However, you can avoid 90% of the trouble by making sure your calls go over the network of a single service provider (by connecting all your offices to that ISP) as most of the trouble that isn't simple outages (get more lines to protect against taht) has to do with the interconnects between networks in one way or another. Of course this ISP has to be a reliable one.