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IP Traffic and Erlang B

Viewing 12 posts - 1 through 12 (of 12 total)
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  • #19795
    Aykut Oztaylan

    I think that calculating ip traffic by using erl-b is wrong, because you can have 30 erl in 30 lines and you couldnt see any overflow in ip traffic, but if you calculate this traffic by using erl-b formula, you find more lines than you use , as well as your lines are enough.

    Isn’t there any formula this calculating ip traffic?

    VoIP Calculator Webmaster

    IMHO, the difficulty comes about, because VoIP is all about trying to converge a technology which is basically circuit switched (voice) into an environment which is connectionless (IP).

    At the end of the day though, you need to cater for the busy hour voice traffic, and Erlang B tells you the maximum number of voice paths you need. After that figure has been determined, you can consider a convergence strategy.

    That may not be the most efficient approach, but it is what the voice world will expect to see if it it to take this opportunity seriously.

    Just my opinion 🙂

    Carlos Alcocer

    I am a little agree with VOIP WebMaster. But I think the calculation of ports in a VOIP Gateway, must do in three steps.

    First making the Erlang B calculation for conventional telephony and second the calculation for the GW and the third, the bandwidth necessary for your satellite link.

    And what about fax traffic and LAN

    VoIP Calculator Webmaster

    Hi Carlos,

    Thanks for your posting. I understand your first and third point, but what do you mean by the calculation for the GW?

    Carlos Alcocer

    Hi WebMaster:

    Thanks for your reply. In the second step with GW I was refering to the Gateways. You need to calculate the packets per second (pps) you Gateway needs to transfer your information.

    In the third place you make the calculation to have the bandwith required for your link (satellite, MW, etc.)

    Sorry for the omission. I think an calculation example will be truly didactic and may help us to make confident with our calculation.

    Carlos Alcocer

    VoIP Calculator Webmaster

    Got you,

    Is that how gateways are rates (in Packets Per Second)? That’s quite easy to calculate. Maybe we’ll include it.


    Daniel Hernandez Galan

    hello everybody:

    you say that you need to calculate with the erlang method in two parts of the links of VoIP?
    what is the effect of that medition for the blocking prob. if you are considering the erlang method of the typical telephony.??

    Anyway if you have any information about blocking on VoIP, please send it me back!!!

    Henry Setiyawan

    I need formula to calculate the voice channel from minutes to voice channel
    if holding time 3 minutes and no blocking.
    How much PCM that I need ?
    Example : 6000 minutes.

    aykut oztaylan

    hi henry
    you need 121 trunk voice channel

    VoIP Calculator Webmaster

    That answer assumes a blocking of 0.005 and that the 6000 minutes represents the traffic during the busy hour. For other values, try our online Erlangs / Lines calculator at:

    Divide the number of minutes by 60 to convert to Erlangs.


    I’m in the process of finalizing a school project. I used the VOIP calculator. I’m not sure what to do with the results though. B/W =216kbps with 9 voice paths.

    Just a guess
    Do I need a total of 9 voice paths each with a BW of 216kbps? Any help appreciated


    No, it means you need 9 trunks, and that they can be transported through an IP-based network using a total of 216kbps.

    Remember though: this doesn’t include layer 2 overheads (eg. Ethernet, PPP etc), and does not take any header compression schemes into account.

Viewing 12 posts - 1 through 12 (of 12 total)
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