When a VoIP system sounds bad, the internet connection usually gets the blame, and usually it deserves it. But the fix is rarely more download speed. Voice is a small, steady stream of data in both directions, and it is sensitive to delay and inconsistency in a way that email and web browsing are not.
We check the connection as part of every business phone system quote, because the right platform on the wrong circuit still produces clipped words and one-way audio. Here is what we look at.
How much bandwidth does one VoIP call use?
The codec, the method the system uses to compress your voice, decides most of it:
G.711. The standard, uncompressed codec many business systems default to. About 85 to 100 Kbps per call in each direction once network overhead is included.
G.729. A compressed codec using roughly 30 Kbps per call in each direction, with slightly lower audio quality.
Opus and other wideband codecs. Used by many cloud platforms for HD voice. Usage adapts to network conditions, typically within a similar range to G.711.
Size for your busiest-hour simultaneous calls, not your headcount. A 25-person office rarely has 25 calls at once. Planning for 100 Kbps each way per concurrent call, plus headroom, is a sensible rule of thumb. An office that peaks at 12 simultaneous calls needs about 1.2 Mbps up and 1.2 Mbps down for voice.
Video meetings are a different scale. One HD video call can use a few megabits per second, which is why video, not voice, is usually what exposes a thin upload first.
Why upload speed matters more than most plans suggest
Voice uses upload and download equally. Many cable business plans are asymmetrical, with upload a small fraction of download, and that upload is shared with video calls, cloud backups and file sync. When a backup fills the upload, calls are the first thing people notice. Our business internet page compares fiber and cable plans by upload as well as download for that reason.
Latency, jitter and packet loss: the numbers that decide call quality
Latency. The one-way delay between speakers. The ITU-T G.114 recommendation treats up to 150 milliseconds one way as acceptable for most conversations. Beyond that, people start talking over each other.
Jitter. Variation in delay from one packet to the next. Under about 30 milliseconds is a common target. Phones buffer a little jitter, not a lot.
Packet loss. Under 1 percent. Above that, syllables and words drop out.
What matters is how these behave between your office and the provider’s network at the times your office is busiest. A speed test at 7 a.m. tells you very little about 2 p.m. on a Tuesday.
How to test your connection before you switch
Run a VoIP-specific test. Most providers offer one that reports latency, jitter and packet loss, not just speed.
Test wired, at peak time, more than once. Run it from a computer plugged into the network during the busiest hours, on several different days.
Check the router or firewall. Confirm it can prioritize voice traffic, and follow the provider’s guidance on features such as SIP ALG, which some platforms ask you to turn off.
Count your concurrent calls. Your current phone bill or call logs show how many calls overlap at peak.
Decide what happens in an outage. Set calls to forward to mobile phones from the platform, or add a second connection from a different carrier.
What to change if the connection is not ready
Prioritize voice. Quality of Service (QoS) settings on the router or firewall put voice packets ahead of downloads and backups.
Move desk phones to wired Ethernet. Wi-Fi adds jitter, especially in busy offices.
Separate voice traffic. A dedicated voice VLAN keeps phones apart from everything else where the network supports it.
Upgrade the circuit. Symmetrical fiber removes the upload bottleneck. For offices where voice is business critical, unshared fiber such as Lightpath or Verizon Fios is worth pricing.
Add a second carrier. A backup connection on a different network keeps calls running when the primary circuit is down.
If you are keeping an existing PBX, the same rules apply to SIP trunking, with the added step of sizing trunks to your peak concurrent calls.
Where we fit
We check what fiber and cable carriers can deliver at your address, compare phone platforms side by side, and size the two together so the circuit and the system match. Request a quote with your address and seat count, and we will tell you whether your current connection is ready or what it would take.