SIP Trunking Explained: How to Choose the Right Provider and Cut Your Phone Bill

What Is SIP Trunking? A Plain English Explanation

SIP trunking replaces traditional phone lines with internet-based voice connections. Instead of physical copper lines running to your building for phone service, SIP trunks deliver voice calls over your existing internet connection.

How SIP Trunks Replace Traditional Phone Lines

Traditional phone service — whether PRI, T1, or analog POTS lines — requires dedicated physical infrastructure. Your phone company runs copper or fiber specifically for voice, bills you per line, and charges extra for long distance.

SIP trunking virtualizes all of that. Voice calls become data packets traveling over your internet connection, just like email or web traffic. There's no separate physical phone infrastructure to install or maintain.

How SIP Trunking Works with Your Existing Phone System

Here's what often surprises businesses: you don't need to replace your phones. SIP trunking connects to your existing PBX phone system. If you have a modern IP-PBX, it likely supports SIP natively. Older systems can use adapters.

Your desk phones, conference room phones, and extensions keep working. What changes is how those calls reach the outside world — and how much you pay for that connection.

Why Businesses Are Switching to SIP Trunking

Cost Savings

Most businesses save 30-60% compared to traditional phone service. The savings come from multiple sources:

• No per-line charges for physical infrastructure
• Dramatically lower (or eliminated) long-distance charges
• No separate maintenance contracts for phone lines
• Pay only for the capacity you actually use

A mid-size office paying $2,000/month for PRI lines and long distance often drops to $600-800/month with SIP trunking. The math usually works.

Scalability and Flexibility

Adding traditional phone lines means scheduling a technician visit, running physical cables, and waiting days or weeks. With SIP, you can add channels (simultaneous call capacity) almost instantly — often the same day you request it.

Seasonal businesses can scale up for busy periods and scale down afterward. Growing companies add capacity as they hire instead of in large increments.

Disaster Recovery and Business Continuity

When a traditional phone line goes down, it's down until someone fixes the physical problem. SIP trunking enables automatic failover — calls can reroute to other locations, mobile phones, or voicemail when your primary connection has issues.

This integrates naturally with failover internet for comprehensive business continuity.

How to Choose a SIP Trunking Provider

Call Quality and Network Reliability

Voice quality depends on network quality. Ask potential providers:

• What's their network architecture? Redundancy matters.
• Do they offer Quality of Service guarantees?
• What's their uptime track record?

Request references from businesses similar to yours. Call quality problems damage customer relationships and employee productivity.

Why Your Internet Provider Matters for SIP

Here's something many businesses learn the hard way: SIP call quality depends heavily on your internet connection. If your internet has jitter, packet loss, or insufficient upload bandwidth, your calls will sound terrible regardless of which SIP provider you choose.

This is why the best SIP implementations come from providers who handle both your internet connection and your voice service. They can configure QoS end-to-end, prioritizing voice traffic from your network to theirs. When internet and voice come from different providers, neither can fully solve quality problems.

Compliance: E911 and STIR/SHAKEN

E911: Enhanced 911 compliance is critical. Your provider must be able to transmit your location information to emergency services. Verify their E911 capabilities, especially if you have multiple locations or remote workers.

STIR/SHAKEN: This caller ID authentication standard is now required. It prevents your legitimate business calls from being flagged as spam. Learn more about STIR/SHAKEN and verify your provider is compliant.

SIP Trunking vs. Hosted PBX vs. UCaaS: Which Is Right for You?

SIP trunking keeps your existing phone system and changes only the connection to the outside world. Best for: businesses with working PBX systems who want to cut costs without replacing equipment.

Hosted PBX moves your entire phone system to the cloud. Best for: businesses without a PBX or with aging equipment that needs replacement.

UCaaS (Unified Communications as a Service) adds video, messaging, and collaboration to hosted PBX. Best for: businesses wanting an integrated communications platform.

SIP trunking is often the fastest path to savings because it works with what you have. It's also a common stepping stone — businesses start with SIP trunking, then later move to hosted PBX or UCaaS when their current equipment reaches end of life.

The POTS Sunset: Why SIP Trunking Matters Now

Major carriers are actively retiring copper POTS (Plain Old Telephone Service) lines. AT&T, Verizon, and others have announced sunset dates for analog service in many areas.

This affects more than just phones:

• Alarm systems connected via POTS lines
• Fax machines
• Elevator emergency phones
• Building entry systems

Businesses waiting for forced migration will have less leverage and fewer options than those who switch proactively. If you're still on POTS, the time to plan your transition is now.

Making the Switch to SIP Trunking

Switching to SIP trunking is less disruptive than most businesses expect. The typical process:

1. Assessment: Evaluate your current phone system, call volume, and internet capacity
2. Number porting: Transfer your existing business numbers (takes 1-3 weeks typically)
3. Configuration: Connect SIP trunks to your PBX and configure settings
4. Testing: Verify call quality, failover, and 911 before cutover
5. Go-live: Switch production traffic to SIP

Most businesses complete the transition with zero downtime and immediately start seeing cost savings.

At Tierzero, we provide SIP trunking as part of our integrated voice services. Because we also provide internet and managed network services, we can ensure call quality from end to end. We manage 1.4 million calls per month and have since 1997.

Contact us for a quote on SIP trunking — we'll show you exactly what you'll save compared to your current phone bill.