VoIP Bandwidth/Traffic Usage

VoIP Bandwidth/Traffic Usage
Photo by Taylor Vick / Unsplash

Voice over Internet Protocol (VoIP) systems are known for their efficient use of bandwidth. Unlike traditional telephone systems that require dedicated circuits, VoIP digitizes voice signals and compresses them into data packets. This compression significantly reduces the amount of bandwidth needed for voice communication. On average, a VoIP call consumes around 100 kbps (kilobits per second) of bandwidth, making it feasible even on modest internet connections. However, the actual bandwidth usage can vary based on factors such as the codec used, call quality, and additional features like video conferencing. It's crucial to have a stable internet connection to ensure the smooth functioning of VoIP systems and avoid call dropouts or quality issues.

Bandwidth per Codec:

  • G711 Codec: 90 kbps symmetric/call
  • G729 Codec: 35 kbps symmetric/call

Video Meetings Upstream:

  • Up to 3Mbps for video
  • 40kbps for audio

Video Meetings Downstream:

  • 2.5 Mbps for "On Stage" video in high quality
  • At least 500kbps for one incoming stream at the lowest quality
  • 200kbps per thumbnail stream (excluding on-stage)
  • 40kbps for audio

Downstream max bandwidth in a conference of n people would be 2.5Mbps + (n-2)*200kbps + 40kbps

Please make sure you have 50% of your available bandwidth free to accommodate any spike in usage. Always assume that at least 35% of your users are on call at any time. However, depending on your company's use case, you may have a higher percentage.

Note: When setting up devices to use an uncompressed voice CODEC, enable both G.711a law and G.711μ law capabilities available on the device. This prevents call quality loss by eliminating transcoding of international VoIP calls. This has no impact on bandwidth requirements, as either choice uses 80 Kbps per call. Transcoding does increase latency.

To estimate the network bandwidth required to support a VoIP station:

  1. Choose the CODECs you plan to deploy in your network.
  2. Multiply each CODEC's bandwidth requirements by the number of simultaneous calls the network must support. For example, if you are using a G.711a/μ CODEC, and you need to support 100 simultaneous calls, then multiply 90 Kbits per second by 100 calls to calculate that you need 8.79 Mbps of symmetrical transmit-and-receive bandwidth to support the estimated call volume.
  3. Add the bandwidth required to support VoIP traffic to the bandwidth required to support your existing network traffic.

When calculating total network load, be sure to include all applications that use the network, especially applications with high bandwidth requirements (such as video conferencing).