Bandwidth used for VoIP is determined by the codec used to convert an analog voice/fax signal to digital data packets. Intermedia uses a codec called G.729 for voice calls by default.  We also use G.711 for fax and some voice calls where the other telephone carrier does not support G.729.
Having the proper internet speed is critical for the quality of your VoIP calls. The minimum internet connection speed required for VoIP is between 90 kbps to 156 kbps.

Note that speed alone does not guarantee optimal results for VoIP.

Your phones need a consistent, reserved amount of bandwidth for excellent call and fax quality. Even just 1 computer on an internet connection with fast bandwidth speeds can use all of the bandwidth in bursts or frequently, depending on what you are doing on your computer(s). This creates a bottleneck that causes your phones calls to drop, audio to cut in and out, faxes to fail, and many other call or fax-related issues.


  • You have 3 phones, 1 fax adapter, and 1 computer.
    • (3 phones) * 90Kbps + (1 fax adapter) * 100Kbps =
      • 370 kbps download minimum needed.
      • 370 kbps upload minimum needed.
      • You use the numbers above to then setup Bandwidth Management on your router to stop your 1 computer from using all the bandwidth. 

For a table that calculates the minimum bandwidth requirements for you, click here.

  • Make sure to use these bandwidth numbers to setup Bandwidth Management (BWM) to ensure excellent call quality. 
  • The steps to setup BWM varies by the router. 
  • However, our Recommended Routers all have BWM and have instructions on how to set it up.

If you do not have a Recommended Router and want to know how to setup BWM, please contact your IT or the manfacturer of the router for instructions.

For more information on Bandwidth Management, see the article Preventing Call & Fax Quality Issues with Bandwidth Management.

For more information on audio quality issues, see the article Call and Fax Quality Issues (QoS).

Additional Resources: