What amount of Bandwidth to allocate for 3 to 4 concurrent calls and how to setup in SonicWall

We have a small office of about 20 VOIP ringcentral phones.  I think that at max, 3 concurrent phone calls happen at a given time.  Perhaps 4 on the busiest moment.  What would be the appropriate amount of bandwidth to allocate for Qos on my sonicwall Bandwidth Management screen.  I have a hard time understanding how this screen is explained so if someone is able to explain what Realtime is and Medium and Guranteed vs. Maximum/Burst that would help.  Thanks
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Mal OsborneAlpha GeekCommented:
This depends a bit on the codecs in use, a voice channel can use anywhere from about 20Kbps to 100Kbps. I usually allocate 64K per concurrent channel. This is nearly always enough, and can of course be increased if users complain about the odd syllable missing. On the pother hand, if you have a heap of bandwidth, might as well allocate ample.

So, my answer would be 256Kbps if you have less than 5Mbps up or down, 400Kbps if you have ample bandwidth.

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