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
. 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.