In the European Union, the treatment of VoIP service providers is a decision for each national telecommunications regulator, which must use competition law to define relevant national markets and then determine whether any service provider on those national markets has "significant market power" (and so should be subject to certain obligations). A general distinction is usually made between VoIP services that function over managed networks (via broadband connections) and VoIP services that function over unmanaged networks (essentially, the Internet).[citation needed]

When shoppers ask which is the best VoIP service or who are the best VoIP providers, no two answers will ever be the same. Keep in mind, that the best service for one individual or business, might not be the most ideal for you. It’s all about finding a VoIP provider that can cater to your specific needs. Users should consider these factors when comparing VoIP providers:
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SIP is built to work on a peer-to-peer (meaning endpoint to endpoint) basis. Those two points are called the "user-agent client" and the "user-agent server." Remember that those points can be swapped, so that in SIP, the endpoint making the call is the user-agent client initiating the traffic and endpoint receiving the call is the user-agent server receiving the call.
As always the best place to start is at the beginning! The following buttons provide access to some of our best guides and tools for getting started with VoIP. These articles give a great background into VoIP, help you understand all the basics, and answer most people questions. The VoIP/Speed test tool performs a test of your Internet connection and provides a great indication of how well VoIP will work at your home. We highly recommend running this test.
Fortunately, most of the providers reviewed here have engineering staff that will contact you as part of your setup process to help your IT staffers test and optimize your network prior to deploying their solutions. That's definitely something we recommend, but there are steps you can take now to prep your LAN for VoIP and make the deployment process that much easier.
VoIP solutions aimed at businesses have evolved into unified communications services that treat all communications—phone calls, faxes, voice mail, e-mail, web conferences, and more—as discrete units that can all be delivered via any means and to any handset, including cellphones. Two kinds of service providers are operating in this space: one set is focused on VoIP for medium to large enterprises, while another is targeting the small-to-medium business (SMB) market.[13]
However, for many businesses there's a need to route calls to the PSTN and other analog phones that might remain in use, too. This may mean a PSTN gateway, or even a hybrid PBX, where there's at least a small telephone switch located on-site. Note that these days, a PBX looks exactly like the other servers in your data center, except with an attached means of handling local and analog phones. Many small businesses, however, are avoiding on-premises PBXes partially due to cost savings and partially because the capabilities offered by all-cloud systems are more than advanced enough for their needs. Some virtual cloud PBXes can handle PSTN connectivity without on-site hardware requirements.

VoIP can be used for free with computers and even, in some cases, with mobile and landline phones. However, when it is used to completely replace the PSTN service, then it has a price. But this price is way cheaper than standard phone calls. This becomes thrilling when you consider international calls. Some people have had their communication costs on international calls cut down by 90% thanks to VoIP.
One advantage of the traditional landline services is that electrical power is sent over the telephone wires so your phone service is isolated from your house power. This meant that your phone service would continue to work if your house power went out. However, with VoIP, power is used not only for the ATA, or the IP phone, but it is also used for your Internet modem and router devices. No power also typically means no Internet service.
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