Hello again,

I'm looking to save some money by considering alternative phone solutions. I should preface this by saying that what I don't know about telephony could fill the Library of Congress.

Currently, we have a traditional phone system. 6 lines, 5 of which feed into a call center, the other for fax. We've got a toll-free number as well.

I would like to look into VOIP solutions and replacing the telephony hardware with software (asterisk.org). I'm not quite sure how the concept of multiple-lines works in a VOIP situation, but obviously, we would need one line to cascade down to the next if the first one is in use.

I've looked into Skype, with one or more SkypeIn numbers (if they can be configured to cascade). It also looks like they're working on a Skype/Asterisk solution that is going to have a Beta release in October. Plus, we have to find out if our toll-free number can be mapped to a VOIP number. It looks like asterisk can plug into any existing VOIP setup, however, so I don't know if it currently works with Skype or not.

Also, I have no idea how the fax thing works with VOIP. Also, we moved to a remote DC recently and we've found that for our office space, a cable modem has been ample. When we start talking about multiple VOIP lines, I don't know how much that will affect our bandwidth needs.

Has anybody done this at this level of complexity? If so, what providers have you been happy with and have you found the service to be reliable and cost-efficient?

Thanks

Asterisk can connect to both SIP and IAX VoIP "trunks." There are many SIP providers out there, and most support several concurrent calls. In essence you only need one incoming number, local or toll free depending what you like. There is no need for roll over as with traditional POST lines. Think about it like an email address, several people can email you at once and you can route the traffic bast on source and destination. Billing can be metered or by channel.

The key is to find a decent provider. Things to look out for are latency to their gateway and jitter (which kills audio quality quickly) and packet loss. Test them, see what codecs they use, and if the quality is acceptable. Although you can port your numbers between providers, it does not happen in real time. Find a good one and stick with it. The closer you get to the big guys (Level3, XO, GlobalCrossing, Verizon, ... in the US) the better for you. Fewer middle men, fewer hops, better latency, less potential for trouble.

On your end, you just need a SIP "client" to connect to the service, preferably on a static public IP (avoid NAT if you can). Asterisk can be both a client and a server for your clients (phones). The phones itself can be behind NAT at the same or other location, that's pretty standard. There is no need for any special telephony hardware if you only use VoIP. Make sure you have sufficient bandwidth -- good quality g711/ulaw calls take 80 kbps (including UDP+RTP overhead) per channel/leg.

For reliable faxing, you really ought to use T.38. Asterisk only can do pass through to a T.38 endpoint such as a T.38 capable ATA (SPA2102, etc.). Often you can get away with just G711 (up to 9600 bps) if your latency is low, and there is no jitter. A cable connection may not be good enough. We have good luck faxing with G711 to/from boxes on data center lines, though receiving typically works better than sending.

PS: Skype and SIP don't mix well. There is a clumsy way of using Skype with Asterisk using proprietary drivers, but I wouldn't recommend it.

Luki,

Thanks for the detailed reply. I need to do some research to really understand everything you just said! Sounds like it might be a good way to go with the phones, however. Or maybe I just like it because it's really cool!

I may just try and simplify the whole fax issue altogether and go with a service like RapidFax.com.

asterisk can do all that is done by your regular phone, however you might need proper person to maintain or at least who can get over the phone, if the extra features of asterisk is worth then it is worth deploy such as call recording etc..

hard phone system is more reliable than software

might a reccomend that you have a look at 3cx.

It runs on a standard windows xp pro install and offers most of, if not all the features of traditional PABX systems, and is a lot easier to config than asterisk as you do not have to edit config files, all config is done from an easy to use admin interface, including configuring supported handsets.

We are an authorised partner and I am a fully certified 3CX Valued Professional.

any questions give me a shout, or look at www.3cx.com (http://www.3cx.com)