“Clearly, the future of telephony is the Internet, for which geographic location and distance don’t matter.”
Andrew Sheppard

Voice over Internet Protocol (VoIP) enables you to use the Internet for making phone calls. Calls from one VoIP phone to another are free and long-distance calls to a landline can typically be made for the price of a local call. VoIP also enables you to receive calls anywhere you connect to the Internet.

What Do You Need?

VoIP telephony requires reliable broadband connection to the Internet with a speed of at least 128 Kbps in the upload direction. In addition, there are three different types of hardware to chose from:

1) Peripherals, such as USB handsets, are relatively cheap to buy and plug straight into your computer. Used in conjunction with suitable software, they instantly turn your computer into a VoIP telephone. The most obvious drawback to such a solution is that your computer needs to be switched on to receive incoming calls.

2) Dedicated IP telephones are generally more expensive and function as independent devices on the network. However, setting up an IP telephone behind a router/firewall with Network Address Translation (NAT) can present you with additional configuration challenges.

3) Analog telephone adapters (ATAs) connect your existing telephones to VoIP services. ATAs usually have built-in ADSL modems (Annex A or Annex B, depending on your country) and, in addition to VoIP telephony, are capable of providing the computers in your home with broadband-access to the Internet. In Europe, and probably elsewhere, the ATA currently is the best tool for Voice over IP.

Session Initiation Protocol

Like any other application on the Internet, telephony services need to communicate by an established protocol. VoIP services that use the Session Initiation Protocol (SIP) benefit from the fact that SIP was designed as an open standard. As a result, any SIP-capable device should be able to link up with any other. What this means is that everybody can call anybody else and for free.

Why Not Use Skype?

Skype is a VoIP service with more than 663 million users as of 2011. It helped start the VoIP revolution. However, Skype uses a proprietary protocol that is subject to a number of security concerns and prevents free calls to and from anyone outside of the network.

What about Vonage?

Up until 2007, Vonage held on to the top spot as the largest provider of Internet-based telephony services in the US. Unlike Skype, Vonage does employ SIP to connect your calls. But it is still very much a closed system, because Vonage require you to use their own proprietary hardware and prevent direct connections to and from other SIP-based providers.

Service Providers

Connecting a call over the Internet is the basic task of an Internet Telephony Service Provider (ITSP). Additional services, such as voicemail and incoming numbers that can be dialled from normal telephones, are often available at no extra cost.

Skype and Vonage are by no means the only culprits when it comes to selling their customers short. The fact that a service provider is using SIP to connect your calls does not always equate to a service that is open and free from artificial restrictions. In particular, beware of providers that proclaim to offer a SIP-based service but then disable the facility to call users on other networks for free.

Because dedicated SIP devices can manage up to ten different accounts simultaneously, there is no need to limit yourself to just one provider. Pick and choose to create a mix of services that best suits your telephony requirements.

Expect No Less

So what should you be looking for in a good SIP provider? The first thing to bear in mind is that when it comes to setting things up, SIP is very much like email. On signing up, a provider should issue you with a username, a password, a SIP address and information about their SIP registrar. If any of these are missing or not documented, for whatever reason, just find another provider who does not keep this information from you.

Your SIP provider should offer a gateway to the Public Switched Telephone Network (PSTN), enabling you to make calls from your internet telephone to regular landlines and mobiles. Not all providers charge the same rates, so compare their respective tariffs. Billing should be by the second, and not the nearest minute.

Often there is a telephone number that others can use to call you on your internet phone. Be sure to find out what rates apply to calls to such a number. True geographical numbers are best, as they will always be charged at the same rate as regular numbers with the same area code.

Your SIP address should work exactly as you would expect, in that anyone with a SIP device or compatible software should be able to use the Internet to call you for free. Otherwise, you might as well be using Skype or Vonage and never really experience the power of true Voice over IP telephony.