Use of ITU-T languages in
Nokia
Experiences and Challenges
Colin Willcock
Nokia Research Center
ITU-T Workshop
Geneva, July 2004
colin.willcock@nokia.com
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Contents
• Specification Languages
• MSC
• ASN.1
• SDL
• Testing Languages
• TTCN-2
• TTCN-3
• Future Trends
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Specification: MSC
• used in two ways:
• design and requirements notation
• to clarify interactions of components in a system
(both in standards and in implementations)
• used extensively for the representation of design
and requirements for software object interaction
with messages
• trace output notation
• to show how system behaved(in environments
that naturally support this (=Telelogic tools))
• used with phone trace output to provide a clear
representation of the phones behaviour. A
number of tools are used to provide MSC
representation from phone software trace output.
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Specification: ASN.1
• Used a lot. Partly because it is used in a lot of
standards in mobile communication. But also it has
been found a convenient means to define protocols
and to get codecs generated automatically.
• Used extensively in conjunction with TTCN-2 and
SDL to define data types used in the protocol
software implementation and testing. i.e. both
products and product test systems.
• Internal CASN compiler tools
• SDL. Note: not following Z.105 but defined own
mapping of ASN.1 to SDL data.
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Specification: SDL
• SDL is used to create protocol emulators
for testers. This is enabled by 3G SDL
library project.
• Nokia NET has own version of the SDL that
is is used quite extensively in some
products.
• On the NMP side used extensively for the
design of many protocol software subsystems (embedded and workstation based
simulation). These models are used as the
basis for automatic code generation using
various SDL->C code generators.
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Current Specification Process
Step 1 - System architecture
• functional specification: text with embedded MSC
diagrams
Stage 2 - Protocol specification
• object-oriented analysis and design with UML
• detailed protocol specification as an SDL-model
• messages and information elements described as
ASN.1 protocol data units
• layer interfaces described as ASN.1 abstract service
primitives
Stage 3 - Protocol implementation
• may use code generation from SDL or other methods
based on SDL specifications
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Introduction of TTCN-2 Testing
Since 1993 TTCN-2 testing has been used in testing
of
• GSM network elements: MSC/VLR, HLR, BSC,
MS
• Other 2nd generation mobile phones: D-AMPS
• Transmission systems: V5.x
• IN systems: SSP, SCP
In-house TTCN-2 tool developed with HUT
• first compiler based on DIS version of the TTCN
language in 1990-91
• tight integration with Nokia in-house ASN.1 tools
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Early Experiences on TTCN-2 Testing
 testing with several PCOs: some PCOs are used
as means for triggering test events to other
PCOs
 well-designed test suites can be executed and
analyzed automatically
 TTCN test suites are designed by a test team,
which is independent from the product
development team
 tools for TTCN programming are available
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 development of an ETS based on TTCN ATS still
requires some programming for test adaptors
 TTCN based method is not as flexible for
interactive probing as protocol emulators
 validation of TTCN test suites prior to testing
against SUT is a must
ITU workshop.ppt/ C. Willcock, July 2004
Evolution of TTCN-2 Testing
Test automation has evolved with TTCN
• Modular and Concurrent TTCN in network element
testing
• Improved integration with other languages =>
TTCN-2
• Modelling of PDUs in ASN.1 also for non-ASN.1 protocols
• Cosimulation with SDL as means for test case validation
• MSC tracing of test case executions
• Standardized test suites, especially by ETSI
• Automatic test case generation – still a promise?
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• TTCN testing has expanded to new systems within
Nokia
• GPRS: SGSN
• UMTS: Node-B, RNC, MSC Server, MGW
• VoIP: CPS, HSS
ITU workshop.ppt/ C. Willcock, July 2004
Testing: TTCN-2 Summary
• Still under development at international bodies,
e.g. Bluetooth and the test system for 3G UEs.
• Used extensively in Workstation and HW
platform test environments for testing protocol
software. This includes sub-system integration,
system integration, release, regression and
conformance testing.
• Quite successful in conformance testing but
limitations in flexibility and ease of learning have
stopped it spreading to other areas of testing
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Future Testing Challenges
• Increasing complexity of products
• GSM Specifications
1306
• 3G Specifications
2290
7000
6000
5000
2G total:
4000
3G total:
total:
3000
2000
1000
0
1994
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1995
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1996
1997
1998
1999
2000
2001
Future Testing Challenges
• Pressure to shorten time to market
• New systems and services must be
available quicker
• How can we reduce testing time?
• Pressure to improve quality
• SW outage average time for Network
elements measured in seconds per year
• How can we improve testing quality (and
quantify it)
• New types of testing
• IP based protocols
• Text based protocols
• Unified testing approach for software and
protocol testing
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Why is TTCN-3 Important
•More Productive
• Easier to learn
• Easier to use
•More Flexable
• Not tied to OSI model
• For many types of
testing
•More Powerful
• Extended functionality
• Support for IP
protocol
• Support text-based
protocols
•More Extendable
• Extensibility built-in
TTCN-2
Software
Testing
Functio
Modul
n
e
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Layer
TTCN3
Protocol
Testing
Unit
Intergration
TTCN-3
• Nokia has been from the very beginning actively
involved in the development of the TTCN-3
language at ETSI.
• The first product testers using TTCN-3 where
introduced in Nokia in 2002.
• TTCN-3 especially strong in the text based
protocol area like SIP.
• Used for almost all new test systems
• Investigation about usage in application areas
that are not typical protocol testing such as
software module testing.
• Area of active research and development.
Conversion of test systems from TTCN-2 to
TTCN-3 already started.
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Future Trends: Specification
• Short term
• UML 2.0 tools will mature and the gaps will be
filled to enable UML to be used not just at the
abstract specifications (requirements) phase
but further down towards implementation
• Medium Term
• As UML 2.0 tools mature and become
available there will be a general move from
SDL to UML for functional specification
• Long Term
• UML will become the glue which finally
enables MBD to be realised
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Future Trends: Testing
• Short term:
• Replacing TTCN-2 in functional and
conformance testing as standard language.
• Increasing use within the IP world especially for
text based protocols
• Possible key technology in the IP/telecom
convergence.
• Medium term:
• Expanding from pure protocol testing to
software testing and interworking testing.
• Possible key technology for unifying testing
technology across whole product development.
• Long term:
• Real time and performance testing? (European
INTERVAL project)
• Integration with UML (UML testing profile)
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