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Erlang B |
  
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Erlang B |
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The Erlang B Traffic Model is an analytical model for calculating call blocking. It makes the following assumptions:
| • | Calls are presented randomly to a trunk group (Poisson arrivals) |
| • | Call times are fixed or are exponentially distributed |
| • | Blocked calls are cleared |
The assumption that blocked calls are cleared is only valid if calls overflow to another trunk group (for instance, calls to a private network link overflow to the public PSTN telephone network if all trunks on the private network are in use). In practice, this is often not the case. However, if blocking is low the error introduced by this assumption is small. The Extended Erlang B model specifically addresses issues of caller retries and can produce more accurate results under these circumstances.
The Erlang B traffic model analyses the relationship between three variables, and each of these variables is represented by a either an argument or result of an Erlang for Excel function. If two figures are known, the third figure can be calculated. The three variables are:
See also
Extended Erlang B traffic model