Voice over IP as a technology is closely tied to the internet, and almost as old. It has been a working technology which was used in enterprises as early as the 1990s. The technology has since grown and takes advantage of the developments of the internet in enabling advanced IP telephony with multiple users at the point of origination or termination.
SIP Trunk lines
With SIP trunking, you can setup a SIP-enabled private branch exchange (IP-PBX) enabling VoIP calls for multiple users within your company. The technology is transparent to the users. They can make outbound or receive inbound calls up to the limits of their internet bandwidth, without knowing that their calls are routed through the internet. One reason for this is that the calls have their phone numbers, or at least, the IP-PBX does. Getting the public domain call through to the private IP-PBX system is usually left out to the asterisk SIP provider.
SIP Trunk Class for VoIP
There are different service providers or different sizes for VoIP, whether for enterprise-class deployment or small office/home office users. Those who require SIP trunking usually are medium to large companies which require long distance communication or international phone numbers. These companies typically include travel agencies, hotel chains, multinationals, call centers, customer support and technical support, as well as companies with regional branches. The need for the company to maintain a single phone number is an important consideration.
There are varied strategies for SIP trunking, as the trunk line can be located according to a specific area code. Where the public domain telephone number is linked, there is where the segregation occurs. However, the users can be anywhere in the world, as long as the system is properly configured.