Erlang B-formula (or Erlang loss function/formula), first established by Erlang in 1917, has been of continued interest even to this day, mainly because of its immense practical importance in telecommnunication theory. Its usefulness is also found in more recent and complicated technologies like ATM. New light on different aspects of the formula is being thrown and new techniques of computations are being evolved. Some light on its history is also being sought, even today. Many new topics like loss systems, loss networks and so on have been developed – many of these use Erlang B-formula (though Engset loss model does not involve this formula). Several extensions and approximations have been advanced in cases of models where exact Erland loss formula does not hold. In this survey, some interesting developments of the Erlang B-formula are put forward.
