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TTCN-3 and ASN.1 interworking. Analysis of backward compatibility in ASN.1. Géza Horváth [email protected] TTCN-3 User Conference 20 11 7 – 9 June 2011 - Bled, Slovenia. Introduction. Nokia Siemens Networks Joint Venture of Nokia and Siemens Started operations on April 1, 2007

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ttcn 3 and asn 1 interworking

TTCN-3 and ASN.1 interworking

Analysis of backward compatibility in ASN.1

Géza Horváth

[email protected]

TTCN-3 User Conference 2011

7 – 9 June 2011 - Bled, Slovenia

slide2
Introduction
  • Nokia Siemens Networks
  • Joint Venture of Nokia and Siemens
  • Started operations on April 1, 2007
  • 65,000+ employees
  • 75 of top 100 operators worldwide
  • 150 countries
  • 3 billion mobile subscribers and ¼ of
  • world’s voice households served
  • Géza Horváth
  • Release 4 Product Support Engineer
slide3
Agenda

Concept of ASN.1 – TTCN-3

Compatibility of ASN.1

Planning a comparator tool

Result, future

asn 1 introduction
ASN.1 introduction

  • Vendor- and language-independent
  • Recursive notation for complex data types
  • Avoid the transfer of concrete syntax
  • Encoding rules
using asn 1 with ttcn 3
Using ASN.1 with TTCN-3
  • TTCN-3 provides a clean interface for using ASN.1 specifications: ETSI ES 201 873-7
  • Alternative data type and value syntax
  • Implicit mapping: import
  • Internal representation of imported objects
  • Without any lost information
slide6
Agenda

Concept of ASN.1 – TTCN-3

Compatibility of ASN.1

Planning a comparator tool

Result, future

the need of asn 1 compatibility
The need of ASN.1 compatibility
  • INTEGER(1..10)
  • INTEGER(1..10,...)
  • Extension marker ”...”
    • Specification v2 must include v1
  • Two compatible specifications are not necessarily syntactically identical
  • Syntactic differences should be detected
  • Semantics are very bound to syntax
  • Two distinct specifications of the same protocol can be compared to evaluate the impact on the interface
syntactic compatibility between asn 1 specifications
Syntactic compatibility between ASN.1 specifications
  • OPTIONAL keyword
  • Extensible subtyping constraints
  • Permutation of SET components
  • What if v1 does not send the INTEGER to v2?
  • What if v2 sends the value 11 to v1?
  • Without the extensions marker?
  • We should know all the changes on the interface
  • In case of SEQUENCE?
slide9
Agenda

Concept of ASN.1 – TTCN-3

Compatibility of ASN.1

Planning a comparator tool

Result, future

structure of the comparator
Structure of the comparator
  • Parser: syntactic error messages as well
  • Normalization: avoiding circular definitions
  • Transitive closure: checking references, imports
comparator algorithm
Root

Root

PDU 1

PDU 1

statement 1

statement 1

statement 2

statement 2

PDU 2

PDU 2

Comparator algorithm
  • A diff-like (textual) algorithm?
  • Detailed comparison algorithm on graphs!
  • The goal is the find a matching between two trees
  • Nodes of the two trees are numbered
  • A global default mark is assigned to the root
  • It is divided between each branch of the root, and so on recursively
  • According to how each node matches with the corresponding one
    • The mark is inherited completely or
    • Decreased portionally to the result of the comparison
comparator algorithm1
Comparator algorithm
  • Synthesised mark at highest level can be considered as the global level of syntactic mapping
  • Compare each PDU of v1 to all PDU of v2 to determine the best matching
slide13
Agenda

Concept of ASN.1 – TTCN-3

Compatibility of ASN.1

Planning a comparator tool

Result, future

result
Result
  • Simple semantic deductions based on syntactic differences
    • * Only notice, not incompatibility
    • ** In some cases it can be incompatibility
    • *** Incompatibility
  • Important to build up an effective visualization
    • A specification can be very huge
extension for future
Extension for future
  • Complete formalization of all the comparison rules
    • Fortunately the algorithm is easily extensible
  • All the error messages are mainly syntactic
  • Addition of the semantics in order to refine messages
  • Integration with specification environment
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