VoIP

SIP Trunking Explained: A Plain-English Guide

If you own a premise-based phone system like Avaya IP Office, SIP trunking is probably the single fastest way to cut your phone bill without replacing equipment your business already paid for.

What a SIP trunk is

Think of a SIP trunk as a virtual phone line delivered over your internet connection. Instead of copper pairs or a PRI circuit from the phone company, your PBX connects to your carrier through the internet. Your desk phones, extensions, and call flows stay exactly the same — only the connection to the outside world changes.

Why businesses switch

• Cost: SIP channels typically cost far less than PRI or analog lines, and you buy exactly the number of simultaneous call paths you need — not blocks of 23.
• Carriers are retiring copper: PRI and analog prices keep climbing as telcos phase out legacy networks. The question isn't if you'll move, it's when and on whose schedule.
• Flexibility: add channels for busy season, remove them after. Reroute numbers instantly during an outage or a move.
• Keep your investment: a healthy Avaya IP Office system runs beautifully on SIP trunks for years to come.

What you need for it to work well

SIP calls share your internet connection with everything else your office does, so three things matter: sufficient bandwidth, a router/firewall configured to prioritize voice traffic (QoS), and a clean internal network. Skipping this homework is where SIP horror stories come from — with it, call quality is indistinguishable from or better than the old lines.

SIP trunking vs. hosted VoIP

SIP trunking keeps your PBX on site and replaces the lines. Hosted VoIP replaces the PBX itself with a cloud service. If your premise system is solid and paid for, SIP trunks maximize that investment; if it's aging out, hosted VoIP is usually the smarter move. We install and support both, so our recommendation is based on your situation — not on what we sell.

Getting started

A free assessment tells you how many call paths you actually use, whether your internet and network are SIP-ready, and exactly what you'd save. Most businesses are surprised in a good way.