The fast-associate mechanism allows a session connection, including its embedded presentation connection and application association, to be established using a compressed form of the information that would otherwise be sent on the S-CONNECT exchange. The compressed form, called the upper-layer context identifier, is a reference to an upper-layer context specification, which is a definition of the fields of the application, ACSE, presentation and session protocols that would be sent on the full-form connect messages. The upper-layer context identifier may be parameterized to include values for the variable fields allowed by the full form protocols for the upper layers.

Within the ACSE service, the only addition is the presence of a conceptual parameter which summarizes the contents of the User information of the A-ASSOCIATE primitives.