VoIP is the broad term for making calls over the internet. SIP is the technical standard most VoIP calls use, and a SIP trunk is a way of connecting an existing on-site phone system to the internet.
VoIP: the umbrella term
Any phone call carried over the internet is a VoIP call. A hosted VoIP phone system puts your whole phone system in the cloud: users, numbers, menus and voicemail are all managed online, and your phones connect directly to it.
SIP: the language VoIP speaks
SIP (Session Initiation Protocol) sets calls up, manages them and ends them. Most VoIP desk phones and apps use SIP, so in everyday use you will see them described as “SIP phones”.
SIP trunks: for phone systems you already own
If you have an on-site phone system (a PBX) that currently uses ISDN or analogue lines, a SIP trunk replaces those lines with internet-based ones. The phone system stays; only the connection to the outside world changes. Each trunk can carry several calls at once, and you can usually keep your numbers.
Which do you need?
| Your situation | Best fit |
|---|---|
| Older phone system, or no system at all | Hosted VoIP phone system |
| Newer on-site system you want to keep | SIP trunks |
| Staff working from home or on the move | Hosted VoIP, with mobile and desktop apps |
| ISDN lines being switched off | Either; it depends on your system’s age |
Not sure? Tell us what you have and we will recommend the simplest route.