It is possible to define a single transfer syntax that is powerful enough to encode values drawn from a number of abstract syntaxes. ISO defines a set of rules for encoding values of many different types for ASN.1. This set of encoding rules is called Basic Encoding Rules (BER). It is so powerful that values from any abstract syntax described by using ASN.1 can be encoded by using the transfer syntax defined by BER.
Although other transfer syntaxes could be used for representing values from ASN.1, BER is used most often.