TTCN stands for Tree and Tabular Combined Notation. The first edition of TTCN was defined at ETSI in 1992. The notation is defined in the standard ISO/IEC 9649-3. In 1998 a second edition called TTCN2 was released. The current most widely used edition is called TTCN2++.

TTCN defines a test notation, which is used to specify OSI abstract conformance test suites. These test suites describe black box tests for reactive communication protocols and services. ASN.1 (Abstract Syntax Notation) was integrated into TTCN as the data notation that is widely used in many communication protocols.

Yes. As the telecommunications industry becomes more complex and fast moving, you need a flexible, consistent standard to measure new products by. Fast changing telecommunication technologies are causing shorter product life cycles and the demand for more sophisticated test tools for this market is rapidly increasing.

Emerging telecommunications products and services are getting more complex and the number of new possibilities being offered is constantly increasing. These challenges require standardised methodologies, tools and procedures that are powerful, flexible and effective. TTCN has the ability to meet these challenges.

TTCN is a standardised language for describing abstract test suites that is independent of test methods, layers and protocol, making it an ideal language for standardised test suites. It has been used to specify conformance test suites for technologies such as GSM, ISDN, DECT, INAP, TETRA, Hiperlan, 3G, VOIP and VB-5.

One of the most extensive users of TTCN is ETSI, the European Telecommunications Standards Institute.

Other industrial groups have chosen TTCN as their testing standard of choice. For example it is used to specify test specifications for Bluetooth™ and UMTS.

TTCN test specifications are easily available and used by telecom companies, test tool manufacturers, telecom equipment manufacturers, private network operators, research centres and test laboratories. In addition to conformance testing, TTCN is also being used for other functional testing.

The latest version of the language, TTCN version 3 (TTCN-3), is standardized by ETSI (ES 201 873 series) and the ITU-T (Z.140 series).
It has been designed from the ground up to make TTCN more suitable for a wider range of applications. The new syntax and additional capabilities will also attract users from other technology fields. Typical areas of application are protocol testing (for example mobile and IP protocols), service and module testing, testing of APIs, etc.
The TTCN-3 standard includes several (optional) presentation formats. The text-based Core Language (ES 201 873-1) will be the natural choice for those used to a conventional programming environment.