For Voice Over IP (VOIP) is a set of software technologies that enable you to establish and manage a communication audio relying not in normal telephone network, but in Internet.
The reason for the growing interest that this technology is leading to is explained by the significant benefits that its adoption can be used to obtain than the traditional telephony:
* Reduction in operating costs;
* Reduction of investment in infrastructure;
* Increased productivity through new features.
The first advantage, reducing operating costs, is significant mainly for calls that do not begin or end, on a normal telephone utilities. If the VOIP call takes place between two computers (PC, PDA or smart phone) connected to the Internet, you avoid any transit through the normal telephone network (PSTN: Public Switched Telephone Network). Therefore, nothing is due to telephone operators to realize the communication between the parties and, apart from the costs already incurred by either accessing the Internet, the call is totally free.
Another advantage is the significant reduction in investment in infrastructure with the possibility to replace traditional hardware switchboards (PBX) with simple VOIP application software that can provide an equivalent set of functions, if not higher. Applications that implement VOIP PBX features can be significantly cheaper equivalent of their "physical", rather, there are even free. For example, the complete system VOIPonCD entirely based on Linux and open source applications, installs in minutes on a normal PC and is packaged in a virtual appliance to run under the free virtualization software VMWare.
The third advantage, not least important of savings, is that formed by the versatility of VOIP systems. Advanced features like call waiting, call to three, call forwarding, audio can be easily provided by the VOIP software. But the most important fact is that it is trivial even enrich them with new features simply by installing additional software modules or performing an upgrade of existing modules.
The operation is rapid, economic, even remotely possible, reversible. But basically this is not the real news, even the call centers had the hardware software upgradeable. The main innovation of VOIP is that it becomes possible, or economically viable, innovative features like the integration of voice mail and e-mail (messages that arrive via email as attachments), the buttons "call" integrated directly into Web pages (part one click and the phone call), the allocation of a virtual number in another country, with redirection via the Internet to the Italy of the incoming calls on that number, and so on: to make this possible is, from an First, the engagement of telephone service in the context information, on the other the particular structure of a typical flat cost of communications via the Internet.
Standard and proprietary technologies
As VOIP technology is important to distinguish between products based on proprietary technologies and products based on standard technologies. All VOIP systems, to support telephone service, must make, in concert with the other, a series of elementary operations that the PSTN network is running normally at each call.
For example: it must be reported to the incoming call, the identity of the caller, must be a way for the called, to accept or reject the call if the call is accepted must be enabled exchange audio flows between the parties in communication with the need to digitize your voice to pass it and then play it on arrival. Finally, both parties must be able to communicate at any time terminate the call.
This set of operations is carried out according to protocols, which prescribe the times, modes, symbols, forms of encoding and compression algorithms to be used at different stages. For example, the transmission of the audio signal of voice compression algorithms require (to allow the operation even when the network connection is not broadband) and cryptographic algorithms (to obstruct the interception and listening to a talk by VOIP unauthorized third). However, it is obvious that the systems of the VOIP calling and called, in order to be compatible, they must use exactly the same compression algorithms and encryption.
It is precisely on the ground of the protocols and algorithms that are different from the standard proprietary. I first choose to use protocols and algorithms specified, published and periodically amended (if necessary) by international bodies, two products of different manufacturers, which do however refer to the same standards should be compatible.
In the case of VOIP, there are two alternative standards for the regulation of the management cycle of calls are the Session Initiation Protocol (SIP), defined (Internet Engineering Task Force), and H .323, promulgated by 'ITU (International Telecommunications Union). Especially in products intended for consumer or small business, the current trend is to an increasing spread of the simplest and most recent SIP. The .323 H remains more common in products for the enterprise market.
The products based on proprietary technologies do not adhere to standards but adopt its own system, usually patented, to handle calls. This means that these systems can communicate (at least directly) only with systems of the same type: the user is in fact "prisoner" of proprietary technology, which also becomes an effective barrier to entry for potential competitors.
The choice to adopt proprietary technologies are more acceptable in software (often referred to as the soft phone), especially if these products are offered for free, even if tied to a proprietary standard, the user retains the ability to "escape" at any time simply by adopting a another free program. Would be very different if the capital impact the systems had to change hardware. For this reason, the physical cost of VOIP is not always negligible, or based on standard SIP, H.323, or what. VOIP hardware also presented as "for Skype" in most cases, is nothing but a USB audio device equipped with telephone keypad, and the integration with Skype is just the management software.