On Defining Voip Telephone Systems

VoIP sends packetized voice over an IP network. Typically, the IP network serves as a data network as well, resulting in potential quality and security issues. Fortunately, most infrastructure manufacturers offers a collection of quality of service (QoS) and security features to ensure the quality and security of voice transmissions.

The ability to transmit voice over an IP network (for example, the Internet) allows many corporate networks to readily interconnect their sites without purchasing dedicated leased lines between their sites or relying on the public switched telephone network (PSTN), which imposes charges for certain call types (for example, long distance and international calls).

With the advent of VoIP technology, some confusion has arisen around its associated nomenclature. For example, consider the terms VoIP and IP telephony. Both refer to sending voice across an IP network. However, the primary distinction revolves around the endpoints in use. For example, in a VoIP network, traditional analogue or digital circuits connect into an IP network, typically through some sort of gateway. However, VoIP telephone systems contain endpoints that natively communicate using IP.

To further illustrate the distinction between VoIP and IP telephony, consider the drawings below. In the top portion of the figure, the endpoints in the VoIP network are, an analogue phone (connected to an analogue port on a gateway) and a private branch exchange (PBX) (connected to a digital port on a different gateway). Because neither of these endpoints natively speaks IP, the topology is considered a VoIP network. With VoIP, a Gateway or other device takes care of the conversion of Voice into IP packets.

The bottom portion of the drawings shows an IP phone, which does natively communicate using IP. The IP phone registers with a call manager or call processing server, which makes call routing decisions on behalf of the IP phone. Therefore, the bottom topology in the figure is considered an IP telephony network. With IP telephony the VoIP telephone systems take care on the conversion of Voice into IP packets. Realize, however, that some literature might use the terms VoIP and IP telephony interchangeably.

IP telephony replaces traditional phones with VoIP telephone systems and uses call processing software, normally on an appliance, server or cloud based for call control and signalling, in place of PBXs. The IP Phone itself performs voice-to-IP conversion, and voice enabled routers are not required in the enterprise network. If a connection to the PSTN is required, a voice enabled router or other gateway must be added where calls are forwarded to the PSTN. IP telephony refers to cost-effective communication services, including voice, fax and voice messaging applications, transported via the packet-switched IP network rather than the circuit switched PSTN.