It is appropriate now to look at the ISO OSI Reference Model (OSI RM) both because it is important for itself and because it establishes a vocabulary that we will use in the rest of the chapter. The ISO OSI Reference Model and the standards which are associated with it, were drawn up in order to define a series of conventions by which computers of different types, and from different manufacturers could communicate with each other. Manufacturers - especially small ones - are generally favourably disposed to such standards as they enable the creation of an 'open' market for their products, which would otherwise be dominated by proprietary standards over which they have no control. As noted previously, the concept of 'layering' is used to decompose the problem.