Updated November 2026
The short version
- SIP trunking replaces your phone lines but keeps your phone system.
- Hosted VoIP replaces both the lines and the phone system.
- Both run over your internet connection, and you can keep your numbers with either.
What is VoIP?
VoIP (Voice over Internet Protocol) carries calls over an internet connection instead of traditional phone lines. It is an umbrella term. SIP trunking and hosted VoIP are both types of VoIP, so the real question is which setup fits your business.
What is SIP trunking?
SIP stands for Session Initiation Protocol, the standard used to set up, manage and end internet phone calls. A SIP trunk is a virtual phone line that uses SIP to connect your on-site phone system (PBX) to a voice provider's network over your internet connection.
It replaces older physical connections, such as copper lines or a PRI circuit, which carries 23 voice channels over copper. Staff keep their phones and the way they make calls; only the lines behind them change.
What is hosted VoIP?
With hosted VoIP, the provider runs the phone system for you instead of a PBX in your office. Staff use desk phones, a softphone app or both, and the provider manages the features. 5x5 business VoIP includes an auto attendant, voicemail to email, call transfer and forwarding, a softphone app, and compatibility with Zoom and Microsoft Teams.
Key differences at a glance
- What it replaces
- SIP trunking: Your phone lines
- Hosted VoIP: Your phone lines and phone system
- Phone system (PBX)
- SIP trunking: You keep and maintain your own
- Hosted VoIP: Run by the provider
- Equipment on site
- SIP trunking: Your existing PBX and phones
- Hosted VoIP: Desk phones, a softphone app or both
- Features
- SIP trunking: Whatever your PBX supports
- Hosted VoIP: Provider features, such as auto attendant, voicemail to email and Teams compatibility
- Good fit when
- SIP trunking: Your PBX is in good shape and staff rely on it
- Hosted VoIP: Your PBX is aging, or staff work from several places
- Your numbers
- SIP trunking: Keep them
- Hosted VoIP: Keep them
Which one fits your business?
SIP trunking fits if
- Your PBX is in good shape and paid for
- Staff rely on how the current system works
- You want to retire copper or PRI lines without changing phones
- Someone already manages the PBX for you
Hosted VoIP fits if
- Your PBX is aging or costly to maintain
- Staff work from home, travel or use several locations
- You want calls on mobiles and computers with the same number
- You would rather not manage phone system hardware
You can also move in stages. Start with SIP trunking to replace your lines, then switch to hosted VoIP when you are ready to retire the PBX. 5x5 offers both, on the same network and support team.
What to check before you choose
- Your phone system: SIP trunking needs a PBX that can connect to it. We confirm your equipment when we prepare your quote.
- Your internet connection: both options run over it, so call quality depends on it.
- Your numbers: you keep your existing business numbers, and 5x5 helps you port them.
- Special lines: 5x5 replaces aging copper lines for alarm panels, elevators and fax machines with modern service that keeps those devices working.
- 911 rules: FCC rules for multi-line phone systems require direct 911 dialing without a prefix, a notification when someone calls 911, and a dispatchable location sent with the call.
How 5x5 Telecom can help
5x5 Telecom offers both SIP trunking and hosted business VoIP. With SIP trunking, your PBX stays in place and connects to 5x5's voice service. With hosted VoIP, 5x5 provides the phone system too. If you later decide to retire your PBX, you can move to hosted VoIP on the same network and support team.
When 5x5 also provides your internet connection, calls and the network they run on are supported by one team, with one number to call. Our 24/7 US-based support team answers every ticket within 60 minutes.