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What is the minimum BW for VOIP?

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  • #23540 Reply

    I am working with a software product which use VOIP. The tech document claim the application only use 1.7kbps when transmit audio data.

    However, once I start my own research on the internet, the state voip would take 16kbps+8kbps (overhead + 8kbps of G729)= 24kbps.

    So, I do my own test using a software sniffer. I calculated BW when use voice only to 8kbps.

    Now, I am very confuse….
    Please advice 🙂

    #23541 Reply

    Depends in what you call good quality.For the voice service by itself, you have diferent “codecs” that could work from 5.3 kb, 6.0 kb,9.6, up to 32 kb.
    That is the voice only, After that you have the overhead, that could be up to two or three extra kilobits, depending on the equipment and codex.
    You do not get a proporcional gain in quality when you use more bandwith.
    With the new codecs, you will be hard presses to hear the diference betwen a 6kb compressed channel and a regular PSTN call.
    The rule of thumb is that you need around 12-15 kb per call that is active, plus minus 2 to 5 kb.
    Is is not a exact science like the old TDM, where you use the bandwith if you are talking or just transporting silence.

    #23542 Reply

    1.7KB/S? That’s a bit extreme, and I can’t begin to imagine what the quality of a call placed using that B/W might sound like. Using g729 codec with VAD and a byte size of 40 on Cisco gateways requires about 12.5KB/S. Good luck.

    #23543 Reply

    Anyone out there knows of a free software that I can use to check bandwidth from the local ISP?

    I suspect that the local ISP is giving me a smaller bandwidth than what is agreed in the contract.


    #23544 Reply

    Annabelle or Ana, la bella. You could go to Go to the “Tools” section and select “speed test”
    You could build a table with your speed test every day and comapre to other users on the same service around the area or around the country.
    The best test found so far.
    Now, if anyone found a better one , I will try.

    #23545 Reply


    You may try MRTG and you could download from

    I’ve seen may networks admin use the MRTG and even my own company use this to monitor the BW in/out the ISP and my company.


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