The early developments of packet network designs by Paul Baran and other researchers were motivated by a desire for a higher degree of circuit redundancy and network availability in the face of infrastructure failures than was possible in the circuit-switched networks in telecommunications of the mid-twentieth century. Danny Cohen first demonstrated a form of packet voice in 1973 as part of a flight simulator application, which operated across the early ARPANET.[69][70]
The following table provides a high level summary of how residential VoIP service compares to other alternative solutions for home phone service. The table compares this service to a regular landline, a bundled phone service from a cable company such as double or triple play, and a cell phone service. The cell phone is included as some people decide to just get rid of their wired phone and use their cell phone for all calls. Free services such as Skype are not included as they are not effective, like for like, landline replacements in our opinion.
VoIP has drastically reduced the cost of communication by sharing network infrastructure between data and voice.[48][49] A single broad-band connection has the ability to transmit more than one telephone call. Secure calls using standardized protocols, such as Secure Real-time Transport Protocol, as most of the facilities of creating a secure telephone connection over traditional phone lines, such as digitizing and digital transmission, are already in place with VoIP. It is necessary only to encrypt and authenticate the existing data stream. Automated software, such as a virtual PBX, may eliminate the need of personnel to greet and switch incoming calls.
Using a separate virtual circuit identifier (VCI) for audio over IP has the potential to reduce latency on shared connections. ATM's potential for latency reduction is greatest on slow links, because worst-case latency decreases with increasing link speed. A full-size (1500 byte) Ethernet frame takes 94 ms to transmit at 128 kbit/s but only 8 ms at 1.5 Mbit/s. If this is the bottleneck link, this latency is probably small enough to ensure good VoIP performance without MTU reductions or multiple ATM VCs. The latest generations of DSL, VDSL and VDSL2, carry Ethernet without intermediate ATM/AAL5 layers, and they generally support IEEE 802.1p priority tagging so that VoIP can be queued ahead of less time-critical traffic.[16]

In the following time span of about two decades, various forms of packet telephony were developed and industry interest groups formed to support the new technologies. Following the termination of the ARPANET project, and expansion of the Internet for commercial traffic, IP telephony was tested and deemed infeasible for commercial use until the introduction of VocalChat in the early 1990s and then in Feb 1995 the official release of Internet Phone (or iPhone for short) commercial software by VocalTec , based on the Audio Transceiver patent by Lior Haramaty and Alon Cohen, and followed by other VoIP infrastructure components such as telephony gateways and switching servers. Soon after it became an established area of interest in commercial labs of the major IT concerns. By the late 1990s, the first softswitches became available, and new protocols, such as H.323, MGCP and the Session Initiation Protocol (SIP) gained widespread attention. In the early 2000s, the proliferation of high-bandwidth always-on Internet connections to residential dwellings and businesses, spawned an industry of Internet telephony service providers (ITSPs). The development of open-source telephony software, such as Asterisk PBX, fueled widespread interest and entrepreneurship in voice-over-IP services, applying new Internet technology paradigms, such as cloud services to telephony.


These include features like voicemail-to-email (and/or fax to email) which will automatically take your voicemail messages and send them as audio files to your email, making you much less likely to miss important messages. Many companies can also provide you with voicemail transcription to text, which will automatically convert the messages to text in an email, saving you even more time. 

^ Jump up to: a b Mahanagar Doorsanchar Bhawan and Jawahar Lal Nehru Marg (May 2008). "Telecom Regulatory Authority of India (TRAI) Consultation paper on Issues related to Internet Telephony. Consultation Paper No. 11/2008" (PDF). New Delhi India: Telecom Regulatory Authority of India (TRAI). p. 16 (Section 2.2.1.2 PC–to–Phone Internet telephony). Archived from the original (PDF) on October 6, 2014. Retrieved September 19, 2012. An end user is allowed to make PC–to-Phone Internet Telephony calls only on PSTN/PLMN abroad.

Yealink SIP-T54S is an easy-to-use Media IP Phone with a 2.8-inch color-screen and a distinctive appearance and structure. For its simplified and human-friendly design as well as user interface, it brings the IP phone and users more closer and unceasingly boosts the operating experience. With Yealink Optima HD voice technology, T54S enhances its audio quality via adding Opus audio codec, so that it delivers superb audio quality and crystal clear voice communications. Yealink SIP-T54S built with Gigabit Ethernet technology, a built-in Bluetooth and a built-in USB 2.0 port, enhancing collaboration and productivity.
An IP phone or VoIP Adapter (ATA) – You’ll see a wide range of prices between the different providers when it comes to equipment. Some providers have expensive equipment and “freemium” service; others will lease you equipment for free and charge more per month. Between those two, you have a lot of in-between. An IP phone plugs directly into your modem or router, and an ATA lets you use a legacy phone over the VoIP network. You need an IP phone to truly enjoy all the benefits of VoIP calling, which is why VoIP phones are becoming more popular.
Designed for busy executives and professionals, Yealink SIP-T52S is an easy-to-use Media IP Phone with a 2.8-inch color-screen and a distinctive appearance and structure. For its simplified and user-friendly design as well as user interface, it brings the IP phone and users closer to an unparalleled operating experience. With Yealink Optima HD voice technology, T52S enhances its audio quality, adding Opus audio codec delivering superb audio and voice communications.
SIP networks usually have a proxy server and a SIP gateway. The proxy sever helps lighten the functional requirements of SIP endpoints. It also acts as both client and server, but it adds functionality around call routing and policy-based management. SIP gateways handle the routing and connectivity requirements for connecting SIP calls to other networks. Typically, the advanced features of the VoIP vendors we review here are largely based on the proprietary management technology they build into their proxy servers and gateways. By offering VoIP solutions where these elements of a SIP solution are hosted in the cloud, the providers reviewed here have more flexibility in building advanced features since they have more control over deployment and reliability.
Yealink DECT repeater RT30, designed in accordance with Digital Enhanced Cordless Telecommunication (DECT). The repeater can be deployed to extend the DECT radio coverage of Yealink W60B base station significantly in all directions, and when working with W60B, it supports two RT30 cascaded. Clear LED indicators are used to distinguish different DECT statuses. Its elegant design and easy installation are typically suitable to be used in the ambiance of all business environments.
In the United States, the Federal Communications Commission requires all interconnected VoIP service providers to comply with requirements comparable to those for traditional telecommunications service providers.[64] VoIP operators in the US are required to support local number portability; make service accessible to people with disabilities; pay regulatory fees, universal service contributions, and other mandated payments; and enable law enforcement authorities to conduct surveillance pursuant to the Communications Assistance for Law Enforcement Act (CALEA).

Your IT staff will understand the basics of what needs to be done before a VoIP system can be selected and installed. That will include capacity testing on your current pipes and a thorough audit of your organization's network management capabilities to make sure they can support and secure the new flow of VoIP data. But for business-level users, selecting a phone system that will help them keep their various processes moving forward, especially the customer-facing ones, starts with understanding what VoIP really is.
When people mention voice over IP (VoIP) most are thinking about a business phone service rather than home phone. After all, businesses run data networks and that's what VoIP needs to operate. But now that the majority of homes have an Internet connection, that means they're also running a data network, just usually a smaller and simpler one than you'd find at the office. If you're careful about what you buy, you can take advantage of VoIP's key benefits, which include far more features and a much lower price tag than an old fashioned landline.
You've probably been offered a home VoIP solution several times already if you've got cable TV service or if you're getting your Internet access from one of the larger Internet Service Providers (ISPs). Outfits like those love offering voice as the third leg of a "triple play" sales pitch: Internet, TV, and phone. When you see those offerings, what you'll be buying is a VoIP-based phone service, though generally one with slightly fewer features than you'll get from a dedicated VoIP provider because the provider generally isn't focused on their VoIP product, but one of the other two.
A high speed Internet connection is required to "carry" your calls so if you have an Internet outage (or your ISP has an outage) then your phone service will not work. Internet services have improved significantly in the last few years and outages tend to be much less common than they use to be. Again, if you have a cell phone then this may not be an issue for you.
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