Is Your Network Ready for VoIP? Bandwidth, QoS, and PoE Basics

Here’s the uncomfortable truth behind most VoIP complaints: the phones are fine — the network isn’t. Choppy audio, robotic voices, one-way calls, and random drops are almost always network symptoms. Before you migrate to a new phone system (or blame the one you have), run through what voice actually needs.

Bandwidth: the easy part

A single VoIP call uses roughly 100 Kbps in each direction with common codecs — modest by modern standards. Twenty simultaneous calls fit comfortably inside a few Mbps. If your internet connection handles video meetings, raw bandwidth is rarely the problem.

What is a problem: contention. A single large upload — a cloud backup, someone syncing video files — can starve voice traffic on an unmanaged network. Which brings us to QoS.

QoS: making voice traffic first-class

Quality of Service (QoS) is the router and switch configuration that tells your network voice packets jump the line. Voice is uniquely time-sensitive: a lost or late packet is a syllable your caller never hears. Without QoS, phones compete with every download on equal terms and lose at the worst moments.

QoS needs configuring at the firewall/router (prioritize voice on the internet uplink) and, on busier networks, at the switch level too. This is standard network engineering — an hour of configuration that prevents years of complaints.

PoE: how desk phones get power

Modern SIP desk phones draw power over their network cable using Power over Ethernet (PoE). That requires PoE-capable switches with enough total power budget for every phone. Common surprises during migrations:

• Old switches with no PoE (phones need bulky power bricks at every desk)
• PoE budgets that run out at phone #14 of 20
• Consumer-grade switches that technically work and irregularly don’t

If a phone deployment is in your future, audit the switching first.

Cabling: the part everyone forgets

Phones need a network drop at every desk — and that cable’s quality matters. Failing terminations, uncertified runs, and daisy-chained mini-switches under desks all masquerade as “phone problems.” A structured cabling audit (labeled, tested, certified runs) is cheap insurance; our cabling and low-voltage team does these constantly, often alongside a phone rollout.

The pre-migration checklist

Before cutover day of any phone migration:

1. Measure bandwidth under load, not idle
2. Configure and test QoS on the uplink
3. Verify PoE capacity for the full phone count
4. Test the cable run at every phone position
5. Check firewall SIP settings (SIP ALG, often better disabled, is a classic call-drop culprit)
6. Consider a failover internet connection if phones are business-critical

Get it checked before it bites

A network readiness assessment takes far less time than a month of intermittent call complaints. GTech bundles one into every business phone deployment — and runs them standalone for businesses whose current phones misbehave, including inherited systems from unsupported providers. Free consultation: 805-979-9897.