OSI Presentation Layer Support

Earlier in this chapter we noted that in OSI, the parameters of a remote operation were specified in a language called ASN.1. ASN.1 is ISO's (initially CCITT's) response to the perceived need for a language in which to express the syntax of information independent of any particular programming language. In many respects, ASN.1 resembles the data type definition facilities of a programming language. It specifies a range of primitive types (integer, boolean etc.) and constructors (sequence, set etc.) via which more complex types can be built. Many standard OSI applications use ASN.1 to express the syntax off the operations they support.