# Erlang's loss formula

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- http://id.loc.gov/authorities/subjects/sh2018003010
- http://id.loc.gov/authorities/sh2018003010#concept

### Variants

- Erlang-B blocking formula
- Erlang's formula

### Broader Terms

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### Sources

- found: Work cat: Goode, J.W. Erlang's loss formula and its use in designing packet switched networks, 2005:pages 16-17 (The CS [circuit serving] network structure and operation is based on a century old formula known as Erlang's Loss Formula. The formula computes the probability that all channels in a multichannel system are busy for a given traffic rate. It has long been used in the design of telephone switching systems and is equally valid for design of high-speed packet switched data communications networks. In a network design based on the formula, a 1000 octet packet is logically equivalent to a 10 min telephone call or a 2 h video from a system load perspective. Only the average network load is significant. The formula shows that the loss rate through a switching node can be made arbitrarily low by the specification of the number of channels)
- found: Tarnoff, P.J. Transportation telecommunications, 1990:page 71 (Erlang B -- One of the basic traffic models and related formulas used in the Bell System. The assumptions are Poisson input, negative exponential holding times, and blocked calls cleared. Used for trunk engineering. Also called Erlang's Loss Formula)
- found: Optimization and operations research. Volume 4, ©2009:page 94 (Erlang's loss formula -- Gives the probability of a call blocking, depending on the number of available channels and on the ratio of arrival and service date)
- found: Oxford dictionary of statistical terms, 2006 :(Erlang's formula -- An early result in congestion theory given by Erlang (1917) concerning the degree of hindrance experienced by a telephone subscriber who is unable to effect a call because all lines or channels are in use. The assumption is that the call is then lost and the formula is frequently known as Erlang's loss formula)
- found: Mazda, X. Focal illustrated dictionary of telecommunications, 1999 :(Erlang's loss formula -- The formula calculates the probability that a call arriving at a network would find that the link is full and so it would be lost)
- found: Braun, D. Efficient routing of telephone calls in a circuit-switched network, 2000:page 13 ( ... The expected number of blocked calls is calculated using the Erlang-B blocking formula, also known as Erlang's loss formula)

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### Change Notes

- 2018-11-24: new
- 2019-03-14: revised

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