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Testing and Test Control Notation Version 3 (TTCN-3) is an internationally standardized testing language from ETSI Technical Committee MTS. This programming language has been used for more than fifteen years in standardization as well as in the industry, and it was developed predominantly for the testing process in the telecom industry. But this testing technology applies to a variety of application domains and different types of testing. It is proven to work in very large and complex industrial tests like in 3G network elements.

Reach in India
Since TTCN-3 is the only contemporary standard testing language, it has a huge potential in India and around the world. Above all, this is well supported by ETSI, making it the default choice for OEMs and system integrators at least for new technologies like LTE. Telecom is one of the oldest and mature verticals. Almost everything has a standard in the telecommunication world. Telecom standards are quite strict and rigid, and telecom implementers follow these standards quite religiously. TTCN-3 is the de facto testing language used to specify the test specification for these telecom standards. So TTCN-3 and testing go hand in hand at least for the telecom conformance testing.

Jayakishor Bhanja, senior consultant, Wipro Technologies says, "India being a testing hub, most of the telecom vendors, both equipment and T&M vendors, use Indian IT companies' testing services. TTCN-3 will play a significant role in the Indian telecom service industry. TTCN-3 is extensively used in the protocol conformance testing. About 70% of telecom testing is still a greenfield for TTCN-3. With the increasing awareness about TTCN-3 especially in India, testers will explore the greenfield."

Vaidyanathan R, test department head, CRD BL, Huawei Technologies says, "TTCN-3 has been adopted as the testing language for LTE as recommended by ETSI. We see a rise in LTE deployment in the coming years. Currently, LTE is having a lab and field trails in European countries and will also see deployment in India. So, there is a huge market demand for TTCN-3 in the coming times which will eventually grow as the LTE market grows. We see TTCN-3 market driven by the technology growth where India might witness more growth in LTE testing." Other sectors like banking also can find TTCN-3 beneficial. So, definitely market potentiality for this testing language is big in India.

Application Areas
TTCN-3 has a nostalgic relationship with the telecom vertical as TTCN was developed predominantly for the telecom vertical only. However, TTCN-3 also has a wide acceptance across many other verticals. TTCN-3 is used at ETSI for the conformance test implementation for the following protocols including Session Initiation Protocol for VoIP, IPv6, DHCP, digital mobile radio and digital private mobile radio, WiMax, 3GPP IMS user equipment, TISPAN IMS network with ISDN and ISUP, LTE, open mobile alliance.

Mahesh Baluni, director, engineering, Aricent says, "TTCN-3 is a widely accepted standard testing programming language which can be used by OEMs, application developers, test measurement players and service providers. It can be used for conformance testing of network elements as well as terminal equipments. Typical areas of application for TTCN-3 in telecommunication are testing of protocols, services, application programming interfaces (APIs), and software modules." TTCN-3 is not restricted to conformance testing and can be used in areas such as interoperability testing, robustness testing, performance testing, regression testing, system testing, integration testing, etc.

Vaidyanathan R, Huawei Technologies says, "TTCN-3 finds application in numerous areas of telecommunications. The areas span across legacy fixed line, wireless domain, and VoIP domain. Basically, TTCN-3 is an effective testing language and framework for protocol suites conformance."

The legacy fixed line area includes adoption in IMS domain testing of CSCF servers. There are a number of test suites application in the signaling system no 7 (SS7) domain, access domain -V5.x, ISDN and plain PSTN switching. In the wireless domain, TTCN-3 is highly flexible to be used for GSM signaling testing to 3GPP LTE network testing. TTCN-3 has been officially adopted as the testing language for testing LTE by ETSI. This will see large scale application of TTCN-3 in this area. In the VoIP domain, the TCCN-3 structures enable it to be used for VoIP domain protocols such as SIP, RTSP, H.248, H.323, MGCP, etc. This has also been designed for UE. TTCN-3 is also used for SIGTRAN protocols, enabling the testing of 'signaling backhauling' of traditional SS7 to IP. TTCN-3 is also finding its use in the datacom domain and grid computing technologies.

Choosing Testing Language
There are some criteria telecom equipment manufacturers and test & measurement (T&M) players need to consider while choosing a particular testing language. Generally topics like re-usability, robustness, performance, tool support, etc, need to be considered.

Srinivas Prasad, general manager, portfolio, Sasken says that the criteria to choose a language for equipment manufacturers or T&M players depend upon many things like-do the test cases need to be ported on multiple platforms; are multiple teams going to script test cases; do users of test cases need to understand the tests; are tests mainly functional or they test the message content also very extensively; and are the test cases for internal use or external use.

Assume that we need to choose a test language for a system where we need to port test cases on multiple platforms and it is going to be developed by many people across the globe, and the tests also need to verify message contents extensively. In this case, following are the criteria that should be followed: ease of sharing test suites; ease of porting on multiple platforms; ease of understanding the test cases by users; possibility of using the same language for doing multiple types of test like performance, load apart from functionality; and availability of the experts.

Bhanja of Wipro Technologies says that the testing language should focus on what to test rather than how to test, and it should not be tied to a particular application or its interfaces. It should not be tied to any specific test execution environment, compiler or operation system; and should be abstract in nature.

Baluni of Aricent says that the language should be easy to learn and use. It should be modular to minimize the impact of change with changed specs/standards and better understanding, and debugging should be easy. It should also support dynamic concurrent test configurations and performance testing. Industry wide acceptability is a plus and must in the case of conformance testing.

Since TTCN-3 is specifically developed for testing, it contains all the above features. Apart from this, TTCN-3 offers already developed test suites for various protocols like SIP, IMS, HSS, IP, SS7, SIGTRAN, WiMax, etc. Wide acceptability of TTCN-3 ensures the interoperability with products/softwares from the third party.

For Better Testing
Achieving performance and security is the most important part of any testing language. Security testing in telecom typically involves the ability to invoke ciphering, integrity and encryption algorithms that are available in the libraries. TTCN-3 has a mechanism of external functions whereby the third party security library functions can be invoked from within the TTCN-3 code.

TTCN-3 scripts compiled can take any shape depending on the tool used. It can be a java archive, a c executive; and these can easily address performance and security areas of testing. Baluni of Aricent says that TTCN-3 facilitates the building of complex test cases. However, the performance depends on the way it is used for building the load testing framework. Timers and parallel test components of TTCN-3 can be used for performance testing.

Vaidyanathan R says, "Currently TTCN-3 is not suited for non-functional aspects like performance and security testing. TTCN-3 is more suited for functional testing. However, there are researches going on in the industry to evaluate TTCN-3 for load testing using concurrency framework provided by TTCN-3."

Bhanja says, "TTCN-3 language has imbibed the testing concepts that cater to different kinds of testing, including performance testing and security testing. In performance testing, key performance indicators (KPIs) pertinent to the system under test like data rate, throughput, latency, etc, are measured and compared to benchmarks. TTCN-3 language has powerful computational semantics and has a good collection of in-built library functions for calculations."

Other Standards
There are numerous scripting languages being used for testing in the telecommunications world such as Perl, Python, Ruby, etc. These scripting languages can be basically used for other applications as well besides testing. TTCN-3 is not just a scripting language, but a complete testing framework. TTCN-3 provides complete test compilation, test execution, logging and reporting functionalities.

Vaidyanathan says that TTCN-3 provides complete testing methodology as per the ISO standard. TTCN-3 can be used for defining new constructs and protocol elements (for testing a new protocol), and can be used for simulating the upper tester-service user (UT) and the lower tester-peer protocol element (LT). TTCN-3 also defines its abstraction for socket communication through the use of point of control and observation (PCO). It also provides the definition of timers.

TTCN-3 as a language provides built-in support for flexible test verdict, dynamic configurations, built-in matching operations and helps in compiling time error detection and defined communication mechanisms.

We can compare TTCN-3 with other general purpose test languages like Python. Prasad points out that Python is a general purpose, object oriented (OO) language which can be used for doing coding of any domain. The main strength of Python comes from the powerful standard libraries which make coding very easy and fast. As Python is a GPL which can be used for software testing, lets compare Python with TTCN-3 on basic test language requirements.

TTCN-2, TTCN-3 Vs LTE
The earlier version of TTCN-3 is TTCN-2. TTCN-3 is conceptually based on TTCN-2. TTCN-3 maintains the most important concept from TTCN-2 like Abstract Test Suite (ATS) while removing the use of communication terminology. When TTCN-2 is there, then why the industry has to go for TTCN-3 for testing LTE is a valid question among many. Also, we know that TTCN-2 has already established itself as a test language for communication protocols, and the 3G conformance test scripts from ETSI are based on TTCN-2 only. There are already pools of experts available for using TTCN-2, both at ETSI-MCC and in the industry. There were lots of vendor choices for TTCN-2 as well.

Raghunath Deshmukh, architect, Sasken points out that the usage of LTE varies from being the communication protocol for mobile to network card for PCs. It enables voice calls on a mobile phone to HDTV streaming on TV/PC. Along with SAE, LTE enables homogeneity of various technologies, so that users can roam around doing their job without worrying about which technology is currently active. LTE-SAE is bringing a complete paradigm shift from the technology dependent world to services dependent world. For example, users can buy a voice service from an operator without worrying about the technology underneath. Depending upon the NW planning, the service will be available at some places on UMTS, at some places on WiMax, and at other places on LTE. All will be available with seamless handovers, and of course, a single invoice. This will make the life of users as well as operators easy.

Deshmukh says, "For testing such varied kinds of LTE devices and associated systems, we need a test language which not only tests the LTE protocols, but also the environment with it."

Srinivas Prasad of Sasken says, "For testing hybrid telecom devices, it is not good if we have to use different languages for testing various components. As using many languages means heavy investments on various costly tools as well as on experts who would know the languages well. For this reason, ETSI started working for a unified test language which can be used for testing various components, including communication and general-purpose software. The outcome of this ETSI work is the concept of TTCN-3."

On using TTCN-3 especially for LTE, Deshmukh says, "LTE-TTCN-3 is a perfect wedding; may be an arranged one, but is going to create a win-win situation for the standard bodies, test and measurement companies, regulatory bodies, manufactures and consumers."

Challenges
When TTCN-3 has certain advantages, it also certainly has some challenges. Using TTCN-3 requires a huge investment. Designing a TTCN-3 test framework from scratch requires time, manpower and expertise. Also, the tools (compilers) are quite expensive. Availability of TTCN-3 experts is another problem. In India specially, it is very difficult to find TTCN-3 experts as not many use this language and also because it is not a part of the curriculum in the Indian universities.

Vaidyanathan R of Huawei Technologies says, "TTCN-3 is currently a very specialized language known to few (with the number increasing), hence there is the challenge of adopting it as a testing language compared to other simple and already highly used languages like TCL and PERL, etc. For meeting these challenges, Huawei has been focusing on building the key competency for TTCN-3 and has been using it for telecom related protocol testing."

Bhanja of Wipro Technologies also echoes the same. He says that TTCN-3 language is quite sophisticated, and is supporting a number of testing and programming constructs. It is quite different from the interpreted scripting languages, and therefore one of the primary challenges facing the TTCN-3 community is to develop the skills of testers so that they can write good quality TTCN-3 code. Training plays a vital role in enriching the skills and expediting its adoption in testing projects.

Kannan K
kannan@cybermedia.co.in

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