VoIP - Why You Need A Dedicated ADSL Connection.
Filed under: Trixbox UK Config — blacksheep @ August 21, 2007 10:46 am
Yikes! We can hear your cry of horror already! “Why do I need another ADSL line! I’ve already got an internet connection, I’m not paying for another one!”. One of the main benefits of Trixbox /Asterisk is to reduce call charges and line rental from traditional analogue and digital lines by routing some or all of your calls over the internet. If you have “light” use of your existing ADSL line for internet browsing and email then you can probably get away with using it for VoIP as well. So if your not trying to upload 100mb Cad drawings all day long or you’re just a two man operation browsing the web, then yep you may be fine.
The point is we’ve done some extensive testing and we still think you’d be much better off having a dedicated ADSL line just for VoIP! Lots of businesses simply underestimate how much they actually use their existing internet connection. You don’t want those huge PDF’s you are uploading to a supplier to interfere with your phone calls!
Lets face it you have more than a couple of incoming numbers you are probably already paying out for numerous dedicated analogue and ISDN telephone lines which you can now think about reducing! Replacing ISDN lines with VoIP is very, very cost effective. Last time we looked the line rental for a BT ISDN 2e line is ÂŁ93(ex VAT) per quarter. We think these days that’s just a crazy price to be paying for the privilege of making phone calls especially when you can have an additional ADSL connection for just ÂŁ20 - ÂŁ25 a month. You can make that ADSL connection carry 4 or more simultaneous calls (depending on the your line speed).Â
If you work on the basis of 64K of bandwidth used per VoIP call we are seeing something like the capability of 4 simultaneous calls even on a very poor performing Rate Adaptive (RADSL) connection in our local area. The shorter the line length to the exchange the better upload speed you should see. If your exchange is enabled for SDSL (i.e simultaneous upload and download speeds) then you may find paying the extra cost worth while to get a faster upload speed. You can also play about with the Codec used for your calls which can potentially decrease the bandwidth used by each call, the trade-off will be decreased audio quality, you just need to find a balance you’re happy with.
Who supplies your internet connection can be fairly critical as well. If you go for the cheapest deals then don’t expect great reliability or line contention ratios. If you skimp in this area then believe us, your experience of VoIP will not be a happy one. You’ve saved so much in other areas it just not worth dredging the bottom of the internet supplier barrel on this one! We can heartedly recommend Zen, Demon and Andrews & Arnolds just as we wouldn’t touch Tiscali, Virgin and Orange with a barge pole (That’s simply from personal experience, there are always exceptions!) UK domestic cable connections are not really suitable for VoIP connections either. Although they tend to have much faster download speeds than ADSL their upload speeds actually tend to be a lot slower than ADSL lines! In this area we are seeing cable upload speeds as low as 110K.
A great place to do a line speed check on existing ADSLÂ / Cable connections is http://www.thinkbroadband.com/speedtest.html.
To find out what services are available on your local exchange go to www.samknowns.com (which is an absolutely invaluable resource!)
Maybe your worried about reliability, well its now possible to get virtually the same service level agreements on a ADSL line as a traditional phone line. If someone chops the line, or the ADSL has a fault at the exchange you can get the same fix times just like you had on your traditional phone line and compensation if they’re exceeded. Of course its an additional expense but if your business depends on it its worth while.
A 100% VoIP solution is not for everyone. A lot of our customers choose to maintain a fall back option via an analogue or digital interface card in the PBX to the PSTN . If the internet goes down we can automatically route calls via the cards until the internet connection is restored.
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Trixbox UK Config
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