# tree and tabular combined notation (TTCN)

Tree and Tabular Combined Notation (TTCN) is an internationally standardized test script notation for protocol testing. TTCN provides a notation that is independent of the test method, layers

, and protocols. The TTCN notation has a mechanism to represent time-related states of a network protocol using the Finite State Machine (FSM) in a tree structure

. The activities for the Tree and Tabular Combined Notation started in the 1990s by the International Standards Organization (ISO) and the IEC

. Standardized as ISO standard 9646, TTCN is used to describe the timing of events or tests. Such a test is used to test communicating systems. The abstract syntax ASN.1 is used to describe the data in TTCN.