Because of the bandwidth efficiency and low costs that VoIP technology can provide, businesses are migrating from traditional copper-wire telephone systems to VoIP systems to reduce their monthly phone costs. In 2008, 80% of all new Private branch exchange (PBX) lines installed internationally were VoIP.[9] For example, in the United States, the Social Security Administration is converting its field offices of 63,000 workers from traditional phone installations to a VoIP infrastructure carried over its existing data network.[10][11]
The products and services in this review roundup are focused on business use and because of this either provide some PBX features or serve as full-on virtual PBXes. This may mean, among other things, that they provide service to telephone sets on your employees' desks. Most also support electronic faxing in some fashion, either directly (which can be a significant challenge for some VoIP services) or by simply integrating an incoming fax with your email system. Other popular features are video conferencing and shared meeting software (so meeting attendees not only hear each other but can present presentations or documents in a shared work space).
Let’s face it: the office environment isn’t for everyone. If you frequently work out of office or run a mobile business (like a food truck or pop-up store), you may find that Grasshopper is the best phone service for you. Grasshopper offers iOS and Android apps that allow you to make and receive calls on your cell phone using your business number—that way, you can keep your personal and work communications separate. It’s a great VoIP software for any entrepreneur who doesn’t want or need desktop phones as part of their PBX solutions.
At the VoIP level, a phone or gateway may identify itself with a Session Initiation Protocol (SIP) registrar by its account credentials. In such cases, the Internet telephony service provider (ITSP) knows only that a particular user's equipment is active. Service providers often provide emergency response services by agreement with the user who registers a physical location and agrees that emergency services are provided to that address only if an emergency number is called from the IP device.
VoIP allows both voice and data communications to be run over a single network, which can significantly reduce infrastructure costs. The prices of extensions on VoIP are lower than for PBX and key systems. VoIP switches may run on commodity hardware, such as personal computers. Rather than closed architectures, these devices rely on standard interfaces.[12] VoIP devices have simple, intuitive user interfaces, so users can often make simple system configuration changes. Dual-mode phones enable users to continue their conversations as they move between an outside cellular service and an internal Wi-Fi network, so that it is no longer necessary to carry both a desktop phone and a cell phone. Maintenance becomes simpler as there are fewer devices to oversee.[12]
Like the rest of us, you probably don't like to get hassled with unwanted phone calls when you’re at home. You can also implement “enhanced call forwarding” to reroute and block the numbers that you specify, without the caller having any idea. You also can set up your phone to block international and directory assistance calls, so they don’t bother you at home. 
Be aware, however, that there are significant security implications regarding the use of mobile softphones on employee-owned devices. While it's possible for your employees to simply download the appropriate software from their respective app store, your IT department should be involved with allowing access while also confirming that necessary security steps are taken. Also be aware that there are important reasons not to allow soft phone installations on private devices of any type because you may not be able to remove that phone client if the employee leaves the company, and because local laws may impact how much control you have over the use of the device.
Operators of "Interconnected" VoIP (fully connected to the PSTN) are mandated to provide Enhanced 911 service without special request, provide for customer location updates, clearly disclose any limitations on their E-911 functionality to their consumers, obtain affirmative acknowledgements of these disclosures from all consumers,[65] and 'may not allow their customers to “opt-out” of 911 service.'[66] VoIP operators also receive the benefit of certain US telecommunications regulations, including an entitlement to interconnection and exchange of traffic with incumbent local exchange carriers via wholesale carriers. Providers of "nomadic" VoIP service—those who are unable to determine the location of their users—are exempt from state telecommunications regulation.[67]
Packed with advanced phone system features necessary to operate a small to medium businesses, such as hosted PBX capabilities, desk-to-desk calling, automated attendant systems, call routing and even music-on-hold, Business phone services powered by VoIP technology make it easy for any company to operate with the same level of professionalism customers expect from large scale enterprise systems. Business VoIP systems also include overall Unified Communication solutions to empower the mobility and flexibility needed for any size businesses. With an inexpensive, feature filled phone solutions, your business can operate at a high level on par with large scale systems, without having to worry about the cost.
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]

Communication on the IP network is perceived as less reliable in contrast to the circuit-switched public telephone network because it does not provide a network-based mechanism to ensure that data packets are not lost, and are delivered in sequential order. It is a best-effort network without fundamental Quality of Service (QoS) guarantees. Voice, and all other data, travels in packets over IP networks with fixed maximum capacity. This system may be more prone to data loss in the presence of congestion[a] than traditional circuit switched systems; a circuit switched system of insufficient capacity will refuse new connections while carrying the remainder without impairment, while the quality of real-time data such as telephone conversations on packet-switched networks degrades dramatically.[16] Therefore, VoIP implementations may face problems with latency, packet loss, and jitter.[16][17]
Unlike traditional telephone lines, VoIP numbers can’t be traced by 911 operators. This doesn’t mean you’d be helpless in case of a natural disaster or Sasquatch attack, however. Upon initial setup at a location, you simply need to enter your info manually through the system’s E911 (Enhanced 911) feature, which will attach a physical address to your VoIP number.
By moving to internet phone technologies, companies are not only able to save a lot of money but also improve their communication infrastructure. Small home-based businesses that could never have a fully-equipped telephone system installed in their premises can now enjoy all the benefits at a fraction of the cost. Some VoIP services offer value for money business call plans that are specifically targeted at small home based businesses.

Although jitter is a random variable, it is the sum of several other random variables which are at least somewhat independent: the individual queuing delays of the routers along the Internet path in question. Motivated by the central limit theorem, jitter can be modeled as a gaussian random variable. This suggests continually estimating the mean delay and its standard deviation and setting the playout delay so that only packets delayed more than several standard deviations above the mean will arrive too late to be useful. In practice, the variance in latency of many Internet paths is dominated by a small number (often one) of relatively slow and congested bottleneck links. Most Internet backbone links are now so fast (e.g. 10 Gbit/s) that their delays are dominated by the transmission medium (e.g. optical fiber) and the routers driving them do not have enough buffering for queuing delays to be significant.[citation needed]
Types of Services offered Home VoIP, Business VoIP, SIP Trunking, International Calling Home VoIP, Business VoIP, International Calling Home VoIP, International Calling Plans Small Business VoIP, Residential VoIP, Reseller VoIP, Hosted PBX, Home VoIP, Business VoIP, International Calling Plans Home Phone Service, International Calling, Business Phone Service
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.
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.

Phone.com straddles the line between business and residential VoIP with a bunch of pricing plans suited to families. It structures its packages a little differently than its competitors. Customers can choose between pay-per-minute plans, which are cheaper but have fewer functions, or unlimited plans, which are more expensive but all-inclusive. The pay-per-minute plans come with a 30-day money back guarantee.
In India, it is legal to use VoIP, but it is illegal to have VoIP gateways inside India.[61] This effectively means that people who have PCs can use them to make a VoIP call to any number, but if the remote side is a normal phone, the gateway that converts the VoIP call to a POTS call is not permitted by law to be inside India. Foreign based VoIP server services are illegal to use in India.[61]
A key attraction of VoIP is that it gives these systems the flexibility to work in a wide variety of environments ranging from analog desk phones to softphones piggy-backing on a cell phone. These systems can often also integrate all or part of their softphone clients into other back-office applications, like your customer relationship management (CRM) or help desk platforms. Simply picture the standard interface of such an app that suddenly sports a dial pad and some function buttons as a pop-up screen and you'll have a very basic idea of how some of this works. In addition, these cloud based systems can have a variety of phone numbers in global locations, so that your customers can have free access to your phone at little or no charge.  
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