Телефонията през Интернет има две първостепенни предимства, работещи в полза на потребителите.

• Намаление на цената на телефонните разговори при голямо разстояние. Използвайки безплатен софтуер (например DIALPAD, Skype, ICQ) цената се свежда само до разход към местния Интернет доставчик, като по този начин се елиминират месечните такси и плащания за минутите разговор към PSTN.

Дори от гледна точка на PSTN компаниите употребата на Интернет телефония също съкращава разходите на големи разстояния през международната телефонна мрежа. Ползата на големите компании от доставчици на услуга за телефония (ITSP) е, че спестяванията им стават все по-големи с увеличаване обема на повикванията. Инвестицията за закупуване на Voice Gateway, която да свърже PSTN с Интернет е висока, но технологичното развитие води към системно падане на цените на качествения хардуер. Важно е също и това, че инвестицията е еднократна.

• Мулти функционалност на линията за връзка на потребителя. Много хора днес все още използуват модем, за да се свързват с Интернет и голяма част от тях имат само една телефонна линия. Така те нямат възможност да бъдат едновременно в Интернет и да провеждат разговор по телефона.

Voice over Internet Protocol

From Wikipedia, the free encyclopedia

Voice over Internet Protocol (VoIP) is a general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet or other packet-switched networks. Other terms frequently encountered and synonymous with VoIP are IP telephony, Internet telephony, voice over broadband (VoBB), broadband telephony, and broadband phone.

Internet telephony refers to communications services — voice, facsimile, and/or voice-messaging applications — that are transported via the Internet, rather than the public switched telephone network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end.

VoIP systems employ session control protocols to control the set-up and tear-down of calls as well as audio codecs which encode speech allowing transmission over an IP network as digital audio via an audio stream. Codec use is varied between different implementations of VoIP (and often a range of codecs are used); some implementations rely on narrowband and compressed speech, while others support high fidelity stereo codecs.

Cisco VoIP phone

VoIP technologies and implementations

Voice-over-IP has been implemented in various ways using both proprietary and open protocols and standards. Examples of technologies used to implement Voice over Internet Protocol include:

• H.323
• IP Multimedia Subsystem (IMS)
• Media Gateway Control Protocol (MGCP)
• Session Initiation Protocol (SIP)
• Real-time Transport Protocol (RTP)

The Session Initiation Protocol has gained widespread VoIP market penetration, while H.323 deployments are increasingly limited to carrying existing long-haul network traffic.

A notable proprietary implementation is the Skype network. Other examples of specific implementations and a comparison between them are available in Comparison of VoIP software.

Adoption

Consumer market

Example of VoIP adapter setup in residential network

A major development starting in 2004 has been the introduction of mass-market VoIP services over broadband Internet access services, in which subscribers make and receive calls as they would over the PSTN. Full phone service VoIP phone companies provide inbound and outbound calling with Direct Inbound Dialing. Many offer unlimited domestic calling, and some to other countries as well, for a flat monthly fee as well as free calling between subscribers using the same provider. These services have a wide variety of features which can be more or less similar to traditional POTS.

There are three common methods of connecting to VoIP service providers:

A typical analog telephone adapter (ATA) for connecting an analog phone to a VoIP provider

• An Analog Telephone Adapter (ATA) may be connected between an IP network (such as a broadband connection) and an existing telephone jack in order to provide service nearly indistinguishable from PSTN providers on all the other telephone jacks in the residence. This type of service, which is fixed to one location, is generally offered by broadband Internet providers such as cable companies and telephone companies as a cheaper flat-rate traditional phone service.
• Dedicated VoIP phones are phones that allow VoIP calls without the use of a computer. Instead they connect directly to the IP network (using technologies such as Wi-Fi or Ethernet). In order to connect to the PSTN they usually require service from a VoIP service provider; most people therefore will use them in conjunction with a paid service plan.
• A softphone (also known as an Internet phone or Digital phone) is a piece of software that can be installed on a computer that allows VoIP calling without dedicated hardware.