Internet telephony service provider
Encyclopedia
An Internet telephony service provider (ITSP) offers digital telecommunications service
Telecommunications service
In telecommunication, the term telecommunications service has the following meanings:1. Any service provided by a telecommunication provider....

s based on Voice over Internet Protocol (VoIP) that are provisioned via the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

.

ITSPs provide services to end-users directly or as whole-sale suppliers to other ITSPs.

ITSPs use a variety of signaling and multimedia protocols, including the Session Initiation Protocol
Session Initiation Protocol
The Session Initiation Protocol is an IETF-defined signaling protocol widely used for controlling communication sessions such as voice and video calls over Internet Protocol . The protocol can be used for creating, modifying and terminating two-party or multiparty sessions...

 (SIP), the Media Gateway Control Protocol (MGCP), Megaco
Media Gateway Control Protocol (Megaco)
Megaco is a gateway control protocol. and an implementation of the Media Gateway Control Protocol architecture for controlling media gateways in Internet Protocol networks and the public switched telephone network...

, and the H.323
H.323
H.323 is a recommendation from the ITU Telecommunication Standardization Sector that defines the protocols to provide audio-visual communication sessions on any packet network...

 protocol. H.323
H.323
H.323 is a recommendation from the ITU Telecommunication Standardization Sector that defines the protocols to provide audio-visual communication sessions on any packet network...

 is one of the earliest VoIP protocols, but its use is declining and it is rarely used for consumer products.

Retail customers of an ITSP may use traditional analog telephone sets attached to an analog telephony adapter
Analog telephony adapter
An analog telephony adapter, or analog telephone adapter, is a device used to connect one or more standard analog telephones to a digital telephone system or a non-standard telephone system....

 (ATA) to connect to the service provider's network via a local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...

, they may use an IP phone, or they may connect a private branch exchange (PBX) system to the service via media gateways.

ITSPs are also known as VSP (Voice Service Provider) or simply VoIP Providers.

History

In the United States, net2Phone
Net2Phone
-External links:**...

 began offering consumer VoIP service in 1995.

Before 2003, many VoIP services required customers to make and receive phone calls through a personal computer
Personal computer
A personal computer is any general-purpose computer whose size, capabilities, and original sales price make it useful for individuals, and which is intended to be operated directly by an end-user with no intervening computer operator...

.
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