Question : Some General Questions From A VoIP Beginner

First let me say I was ecstatic to learn that there was a VoIP forum on EE. I nearly yelled out loud. With that I have been reading a good deal on VoIP. I have been exposed to VoIP for a while, I am a Vonage customer and have implemented Asterisk server (non-VoIP implementation) which has in turn given me several trips to voip-info.

I am working on a new project and I would like to get a little more down and dirty with VoIP but can't seem to find some simple answers, hope this post will help.

Question #1
Is there an organization that regulates all VoIP activity? Primarily I have learned that there must be a VoIP gateway to interchange between VoIP and the PSTN. Where I seem to loose sight is in how an actual telephone number fits into the picture. Is there another tier that I a missing?  For instance, if I purchased a soft phone, or compiled one from source-forge, what would be my next step to get a physical number and then route that number to my computer?

Question #2
In terms of a VoIP gateway, are these all hardware devices or can this be a software device? In the last Asterisk implementation I terminated a long distance t-1 using a Digium card. I am wondering if there is a different route with VoIP or if Astrisks can act as such a gateway.

Question #3
In my initial research I have found VoIP and VoIP gateways closely linked to PRI lines. Is this a requirement for large scale VoIP implementations? Large scale being 24 lines…

Question #4
I know that VoIP is based upon the TCP/IP model, with that, is it possible to extrapolate VoIP to the lowest common denominator, so that I can set a phone number to route directly to an IP address? i.e. a listening TCP/IP server?

Question #5
My new project is for a not-for-profit organization and cost is of the essence. I need several incoming lines (equivalent to a dedicated voice T, 24 lines). Would this be a situation that could benefit from use of VoIP? I will most likely be using Asterisks. In terms of incoming bandwidth, would I need a PRI? Or could I run it off of a cable modem?

Please take my questions at face value as they my be misleading or formed incorrectly dur to my lack of understanding. I greatly appreciate any and all responses and assistance. I am currently reading VoIP Fundamentals from Cisco and a good old VoIP for Dummies. I am familiar with voip-info, but if any passer-bys have a good solid link for me to check out that would be great.

Thanks guys, you are great!

C

Answer : Some General Questions From A VoIP Beginner

1) Not really.  Pure-play end-to-end VoIP, for instance one Vonage customer to another (at least I assume Vonage works this way), doesn't ever have to touch the PSTN, and so, in theory, you don't even have to have a phone number, as long as you only want to talk to other VoIP users who share your service - just an IP address.  In order to talk to the rest of the world, however, you've got to have both a gateway, to convert from VoIP to circuit-based POTS or whatever, and a real number.  Those numbers are allocated just like any other telephone number, by the FCC or whoever actually assigns them.

In your example of getting a soft phone, you'd still either have to have a service provider to provide the interconnect and number as Vonage is doing for you now, or be restricted to talking with other pure internet VoIP users.

2) the actual gateway will always have a hardware aspect, just because it's transition from one type of communication to another; there's got to be a TDM bus somewhere to terminate the PSTN circuit.  I'm not familiar with Astricks, but if it can "speak" VoIP, and handle cards to provide termination, it should work, in theory. . . .

3) PRI trunks are not required, they're just common, being generally cost effective.  You can run individual B-1 lines into your gateway, or analog trunks, or whatever your particular hardware can handle on the PSTN side.

4) VoIP is IP-based, obviously (or it wouldn't be called VoIP :-). The actual conversation is carried over RTP (real-time protocol), but the call setup, etc., is handled by some form of signalling protocol, which may vary from vendor to vendor.  SIP is the emerging standard, but others, such as H.323, or various proprietary setup protocols, are probably still more common.  If you're writing your own VoIP client, you'll have to be able to handle compatible signalling with whoever you're connecting to.

5) For this situation, you're really looking at two different questions:  Trunk/non-trunk, and VoIP or not.  

The only way to judge the benefit of a trunk versus separate lines would be cost, really.  And if you're talking about bringing a trunk in, regardless of whether you're doing VoIP or not, you're talking about having a phone system of some kind, on site, that the trunk would tie to.  The other end of the trunk would be at your local phone provider.  In that situation, a cable modem would do you no good.

If, on the other hand, you're talking about using an internet-based service, which is probably possible for that size organization, at least for basic calling features, then you don't need a trunk, just an internet connection of whatever kind, as long as it has sufficient bandwidth.  All of your voice traffic would enter and leave the local site as IP, and would interface with the PSTN at your provider.

As to whether VoIP would be beneficial in the first place in that situation; that's not a matter of trunks versus non-trunks; trunk vs. non-trunk is just a matter of whether it's more cost effective to share a single big pipe, or pay for individual lines for each phone.  But, if you want the features and capabilities of a true phone system, rather than just a bunch of separate lines (things like 3- or 4- digit extension dialing, hunt groups, internal directory services, central voice mail), then you're either looking at putting some kind of system (VoIP or not) on site, or buying some kind of Centrex service from the local telco.

Once you decide that, then you look at whether you do VoIP or traditional telephony.  Either is possible in both the on-site system scenario or the external provider scenario.  In most cases, especially the on-site scenario, I'd recommend VoIP, for the benefits of simplfied cabling and administration, easier adds, moves, and changes, and all the possibilities of converged data and voice.

Hope this is at least somewhat clear.  As you've already discovered, it's not exactly a simple area. . . .