  Suppose that we have two similar files stored on different computers. We need
to send the file from the first computer to the second one trying to minimize
the number of bits transmitted. This article presents a survey of results known
for this communication complexity problem in the case when files are "similar"
in the sense of Hamming distance. We mainly systematize earlier results
obtained by various authors in 1990s and 2000s and discuss its connection with
coding theory, hashing algorithms and other domains of computer science. In
particular cases we propose some improvements of previous constructions.
