So what exactly are the advantages of VoIP? The first is a scaling down of control, as IP telephony functions allow calls from virtually any computer. Not only can individual users call each other through P2P networks like Skype, but their machines can actually become PBX facilities, giving them complete control over call switching and other functionality. With the development of telephony software like Asterisk by Digium's Mark Spencer in 1999, virtually any PC with a traditional telephone or internet connection can be converted into a VoIP PBX ready for configuration. This has bought an end to the era of prohibitively expensive proprietary telephony hardware. Previously computer telephony add-ons would have had to handle voice processing. Now the PC platform carries this function and the hardware necessary is that needed to host interfaces to connect to a PSTN line or main server. Multi-core CPUs now reach over 80,000 MIPS or more. If at least half of the processing dedicated to voice applications, a server with this capacity and a modest level of memory (2GB) can process over 500 channels at a price affordable to ordinary users. A typical home machine might be able to run around 120 channels with echo cancellation. The downside here though is that the whole system is down if the server crashes. This has made some customers reluctant to take on VoIP except as a supplementary resource. After all, many would think twice about relying on computer technology to relay emergency calls unless they had a back-up plan in place. Although there are now many options are now available to increase the resilience of IP telephony platforms, to the point that many major corporations now rely on IP telephony infrastructure.
A second advantage of VoIP is mobility; as your PBX and telephones can be anywhere. A phone in a home study or overseas office works just like the one in the same room as your server. Using analog telephone adapters (ATAs) ordinary house phones can be connected to VoIP networks.
The third and perhaps greatest advantage of VoIP is the ability to eliminate cost. For broadband customers, companies like Vonage, AT&T (CallVantage), and 8x8 have offered national calling for a fixed fee plus international calls for a low per-minute charge. When survival is determined by mimizing the costs of doing business, eradicating cumbersome and expensive telephony resources becomes a must. Service providers that can offer significantly cheaper and more flexible telephony solutions are likely to prosper, especially when older systems have hardware that is expensive or increasingly hard to find.
A forth advantage of VoIP services is that the use of open source languages tools like Asterisk that can offer a wide variety of additional features including auto attendant (interactive call handling by a virtual receptionist), call forwarding (allowing employees to hot desk), automatic routing (based on Caller ID), call screening and voicemail. A recent development here is the inclusion of 'follow me' calling: a user can assemble a list of their various numbers (desk phone, mobile, etc.) and calls can be automatically routed to reach them where ever they are.
With these advantages it is hardly surprising that firms are starting to offer asterisk training [http://www.asterisk-training.co.uk/asterisktraining.html] for voip programmers and solutions for a growing base of business voip [http://www.asterisk-training.co.uk] customers.