VoIP phone calls generally require the same bandwidth in both directions of transmission. If only one or few phone calls are made at the same time, an asymmetric DSL connection is typically still adequate. However, when there are a lot of simultaneous phone calls, the connection should be configured to provide adequate upload and download bandwidth.or VoIP, enough bandwidth must be supplied to allow for the transmission of voice data in real time. A good rule of thumb is to consider 1/10 of your organization is on the phone at any given time, or 100 kbps for every 10 employees.
To check your speed, perform this test: https://www.blueface.com/speed-test/. Run the test twice at peak time and at down time. Do not perform the test over a WiFi connection (lower quality). Recommended value is 100 kbps per simultaneous call.
Download Speed: The download speed is how fast you can pull data from the server to you. Download speed is measured in megabits per second (Mbps) Low download speeds will result in difficulty hearing the person you call or has called you.
Upload Speed: The upload speed is how fast you send data from you to others. Upload speed is measured in megabits per second (Mbps). Low upload speeds will result in issues hearing your caller or the person who has called you.