If your company still runs PRI or T1 circuits into every office, you are likely paying each month for voice channels nobody uses, and maintaining a separate telephone network alongside a data WAN that could carry the same calls. SIP trunking offers a way out. Before you build a case for it, you need to know what equipment it demands, whether your current PBX can stay, and where the SIP trunking cost savings would actually come from in an organization shaped like yours.
This white paper from Level 3 Communications is written for CIOs and telecommunications managers weighing a move from traditional TDM or ISDN voice service to SIP. It explains what a SIP trunk is in practical terms, what it takes to get one, and how to judge whether your enterprise is a strong candidate before you commit budget or sign a carrier contract.
Where SIP trunking cost savings come from
Savings from SIP are often described in vague terms. This paper pins them to three specific mechanisms: converging voice and data on one network, pooling concurrent call paths across sites, and routing calls between offices over your private WAN instead of a carrier network. You'll see why each one matters and which tends to produce the biggest returns.
The section on concurrent call paths is especially useful if you're comparing PRI vs SIP trunk pricing. It explains why PRI capacity comes in fixed blocks while SIP capacity can be set to whatever number your sites need, and why small branch offices are often where the waste hides. It also clarifies where the money is really saved and where it isn't, which matters when a quote shows a higher per-channel price than you expected. Enterprises spread across several time zones get an extra angle to consider.
To make the numbers tangible, the paper walks through two worked examples: a large, multi-state enterprise with a hundred branch locations and a smaller regional business in a single time zone. Each shows total monthly savings and how they break down by source, along with the assumptions that would change the results for your own company.
SIP trunk requirements and PBX to SIP upgrade options
One of the most common reasons companies delay SIP is the belief that every phone and switch has to be replaced. The paper addresses that directly and sets out the realistic paths for different kinds of installed equipment, from current IP telephone systems to recent PBXs to much older ones. It explains how an adapter can bridge legacy gear to a SIP network, and what that means for your existing handsets and wiring.
You'll also learn:
- What a session border controller does, where it sits, and when you might want one at your own premises
- Which WAN capabilities can make or break a SIP deployment, including bandwidth headroom and quality of service for voice traffic
- How primary and secondary trunks, diverse server clusters and automatic rerouting support business continuity and disaster recovery
- Why the precise definition of "SIP trunking" matters when you compare carrier offers
Level 3 also describes features of its own SIP Voice Complete service, such as calling among enterprise locations at no charge, so you can see what to ask any provider about.
Which enterprises gain most from moving off PRI
Not every organization will see the same result. The paper closes with a profile of the ideal candidate, covering company size, how facilities are spread out, the age of telephone equipment, and signs of underused capacity in access trunks or the WAN. It also connects SIP to broader goals like unified communications for a mobile or dispersed workforce, and faster recovery from outages or disasters. If several of those traits describe your business, you'll come away with a clearer sense of how strong your case is.
Download SIP Trunking: How to Get It and Where You Can Expect to Save to get the full breakdown of savings mechanisms, both worked enterprise examples with dollar figures by category, the equipment and network requirements for VoIP in the enterprise, and the candidate profile you can hold up against your own operation. It's a short, practical read that gives you the grounding to talk with carriers and finance on equal footing.