The term VoIP is also used as a noun or verb (see Voice over IP VoIP).  VoIP is widely used by businesses and services, including advanced VOIP providers, and schools increasingly use it. The availability of broadband Internet (4G)-based voice communications through a VoIP system, therefore, provides Internet-based telephony for educational institutions to offer to individuals without upgrading or re-registering their VoIP equipment. Features of an Internet-based telephony system are usually subsumed within the definition of Voice over IP (VoIP) by its proponents. Still, the VoIP service itself is generally not required to be implemented in an Internet-based telephony system. VoIP systems may be incorporated into a retail telephone network, such as a system that provides telephone-service to geographic areas defined by either the provider’s telephone company, an alliance of local telephone companies, or the public switched telephone network (PSTN). Once implemented, VoIP services are integrated at a “high-level” (sometimes called “branch”) level when VoIP features are connected to form a “network.” At the master level, the network performs specific attributes of VoIP (such as transmission protocols such as TCP/IP), and at the intermediate level, the network stores specific details of VoIP (such as the name of an extension provider, its physical address and port, its layer two activation attribute, its DNS server hosts, its DNS server search query database, and the names of or parameters defining the individual components of the voice over Internet protocol (VoIP) service itself).  Some implementations of VoIP services use IP addresses, DHCP addresses, or Teredo/UDP IP addresses.
Internet telephony seems to be increasingly being seen as a complementary service to the PSTN. A VoIP system may be offered for a fee to any customer whose financial need dictates that they do not want to upgrade to the existing PSTN service but is then offered for free to those customers who do. VoIP services are commonly used by businesses and domestic and international customers of ISPs and hosting companies. Broadband telephony services are often provided by Rapid Communications Companies (RCC) in structured messaging services such as TextSecure, IMS — the Short Message Service (SMS) vCard, and instant message services such as SMS Love. Domestic broadband telephony services such as MTS and CTIA’s OnConnect Internet voice service provide local phone (chill line) access over IP networks. In contrast, intra-North American broadband services such as Verizon Frame Relay, Wireline Voice, and CDMA CDMA Express PL Service 12 offered by Mobile Network Operators provide Internet telephone services to some locations in and around the US. VoIP services are increasingly being deployed to boost Internet bandwidth and improve Internet communications and video reliability. VoIP systems can be deployed over the existing Internet backbone or deployed to bypass the existing backbone and take the services to their respective access points.
Generally, VoIP services are categorized as multi-protocol, using VoIP endpoints being typically supported by VoIP clients, by ISPs or (online) phone systems, or both. On the other hand, the used term “VoIP client” is mainly used on the Internet for all applications with a single central API. Single VoIP service providers (known as “VoIP providers”) use their VoIP services as their primary client for their VoIP services.
Many different companies, large and small, both small and large, offer custom VoIP services on the Internet for a fee.  These companies usually advertise on advertised services groups (e.g., Amber, Gabel, Yellow ) so that their services are exclusive to Fido customers only. Some of these services rest on the voice-over-IP (VoIP) technology, most commonly with a little support/modification of existing PSTN systems or “partial” VoIP providers. They usually involve aggressively secondary billing practices contained in contracts that are not very difficult to override. They usually are all set up for dial tone and modems.  VoIP services can be mainly classified into the following three topics: specialized multi-tech support services, wide-area VoIP services, and broad-area VoIP services. Technical multi-tech support services usually cover the use of applications that require low bandwidth or bandwidth that is mainly used by end-users in the first place.