While there are lots of guides available online on the subject of how to start your own VoIP business, this article will focus only on one aspect: technical one. That includes: how VoIP works in general, what components are needed and how to get them right.
VoIP, as the abbreviation says, means Voice over Internet Protocol, i. e. using public internet to carry voice conversations. The idea is several decades old, and during time many technical specifications have been developed to accomplish this, which later either ITU standards or IETF RFCs. Most popular ones were H.323, MGCP and SIP. Of the three mentioned, SIP or Session Initiation Protocol is most widely used today, especially for retail or end to end user connection.
The starting and ending point of the voice call in most of the telephone calls in a phone. Similarly it is in the VoIP case: it is VoIP enabled phone. There are many ways how the VoIP phone may look like: an app in the smartphone, a program on the computer, a physical phone, a device connecting regular phone to the VoIP network etc. Any of these devices as long as they comply with specification (e.g. SIP) can be used as a VoIP phone. The main difference perhaps is just a users preference.
Next, the call is usually passed to some kind of central device which handles addressing, routing, charging etc. In case of SIP it is either a Proxy or Registrar or some kind of combination of both. These devices ensure that calls reach their destinations (i. e. they know at which IP address which phone number is located), makes sure that only authorized phones use their network, and make sure calls are properly billed at the end. There are many other technical details these devices are responsible for, but that is not important at the moment.
Now, with this setup (Phone->SIP proxy/Registrar -> Phone) we have already functioning VoIP network, where people can call between themselves. This is of course very limited setup, as the calls cannot reach outside world, and no calls from outside world can reach us. The connection to the outside world (to the public network, or PSTN) is done via devices known as Gateways, or SBCs in some cases, and they provide connection between different networks, in our case between our small private VoIP network and the world. In practical terms these services are usually provided by 3rd party licensed companies, for a fee, which is in most cases are per-time and/or per-connection based. There are plenty of them, and if you do a web search for "wholesale voip termination", you will sure get lots of offers.
Once you are here, your VoIP users already can make calls to any person in the world. Good progress! Now, what happens if somebody from regular phone wants to call back your VoIP user. That does not work of course, because for a regular user to make a phone call, he needs to know the phone number. But we haven't set any yet for our VoIP users. Yes, and we cannot do, because we cannot just take any random numbers and give them to our customers- we need to have numbers which are recognized and known for any caller from outside number. Again, outside help is needed. The service is called Direct Inward Dialing or DID, and the providers are know as DID providers, and again there are plenty of them. In many cases they are the same companies which offer termination services. They offer ranges of numbers for purchase which, like regular phone numbers are tied to specific country, region or city. Not all countries are available, and many countries impose restrictions on what numbers can be offered via VoIP, but in general there are lots of choices. Get the number from the DID provider and you have your inbound connection established.
Above we have discussed all the main ways and pieces needed to make calls over VoIP: between two users, to the outside world, and from the outside world. There are interconnections needed (termination and DID numbers). What remains is the central part of your network: a SIP Registrar/Proxy and related elements around it to ensure security, addressing, routing, billing etc. Again there are many options to choose from: you can buy ready made software, rent or buy servers in the datacenter and install it. Or you can sign up for whitelabel voip services which will do everything for you. Whatever option you choose, make sure it has some of the important elements in place: SIP registrar/proxy, support for DID numbers, prepaid realtime billing, routing.
In case you decide to go with our cloud based services, please have a look at our Voice Services Quick start guide
