What Is Voice-Over-IP?

Voice-over-IP (VoIP for short) (also known as Internet Telefony) is a telephone service that works over TCP/IP-based data networks such as your broadband connection to the Internet. It is an alternative to POTS - the Plain Old Telephone Service - that traditional landline phones are connected to, and is also an alternative to mobile phones.

Companies that provide VoIP services are commonly known as Internet Telefony Service Providers, or ITSPs for short. One of the key reasons to buy your VoIP service from an ITSP is because the ITSPs provide the means to connect your VoIP phones to the public telephone network.

Although historically there have been competing standards for VoIP, today there are three clear standards used by competing UK Internet Telephony Service Providers.

• SIP and IAX2 are commonly supported by Internet Telephony Service Providers
• Skype uses its own proprietary standards, and currently inter-operates with the wider telephone-using community via the PSTN.

To use a VoIP service, you need:

• A VoIP-capable handset or software on your computer¹⁾.
• A VoIP-capable PBX - either a hosted PBX or your own PBX connected via a SIP trunk or IAX trunk.
• An Internet connection, such as Gradwell Broadband or broadband from another supplier.

That will allow you to make calls to / receive calls from other VoIP users. If you also want to receive calls from traditional telephone users (landline or mobile phone users), you will also need to purchase a PSTN telephone number.