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Laboratory of Advanced Network Technologies. MSC & SCStudio Mat u s Madzin Faculty of Informatics Masaryk University Autumn 2011 1 / 30 Message Sequence Chart Message Sequence Chart (MSC) is a formalism for communication

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Laboratory of Advanced Network Technologies. MSC & SCStudio

Mat´ uˇ s Madzin

Faculty of Informatics Masaryk University

Autumn 2011

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Message Sequence Chart

Message Sequence Chart (MSC) is a formalism for communication description between a number of independent components.

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Message Sequence Chart

Message Sequence Chart (MSC) is a formalism for communication description between a number of independent components. Standardized by ITU-T as the Z.120 recommendation 1993: the first version ... 2011: current version

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Why?

Why should we use any formalism?

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Why?

Why should we use any formalism? automatic/computer processing model checking equivalence checking testing simulation theorem proving

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MSC Components

Which components does MSC provide for the user? communicating processes message ordering time information high-level form

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Advantages

What MSC is good for?

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Advantages

What MSC is good for? Both human and computer readable formalizm for: basic behaviour demonstration (use cases), high level system behaviour description, test case specification, and (test) log visualization.

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Disadvantages

What MSC is NOT good for?

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Disadvantages

What MSC is NOT good for? detailed specification (before implementation), hierarchical structure of communicating entities, implementation details (primitives for communication, detailed data manipulation), etc.

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Message Sequence Chart (MSC)

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Sequence Chart Studio

MSC drawing and verification tool developed at FI MU.

http://scstudio.sourceforge.net

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Message Sequence Chart (MSC) - semantics

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Message Sequence Chart (MSC) - semantics

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MSC Properties

What is an unwanted behaviour/property?

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MSC Properties

What is an unwanted behaviour/property? Fundamental problems in the specified model, e.g. an implementation of the model does not exist in the given environment.

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Acyclic/Cyclic property

cyclic dependency among events unrealizable in any environment

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Acyclic/Cyclic property

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FIFO/non-FIFO property

verleaping messages

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FIFO/non-FIFO property

verleaping messages

unrealizable in an environment preserving message order

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FIFO/non-FIFO property

verleaping messages

unrealizable in an environment preserving message order

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FIFO/non-FIFO property

verleaping messages

unrealizable in an environment preserving message order realizable in an environment with P2P channel but unrealizable in case of a global channel

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Race Condition

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Race Condition

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Race Condition

Informally, race is when some receive event can come earlier.

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Solution #1 - Coregion Construction

Let us demonstrate that some events are not ordered.

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Solution #1 - Coregion Construction

Let us demonstrate that some events are not ordered.

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Solution #1 - Coregion Construction

Let us demonstrate that some events are not ordered. Events in a coregion are not ordered; except of related by general

rdering.

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Solution #2 - List/set of all possibilities

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

these events are not ordered!

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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High-Level MSC (HMSC) - ITU-T Z.120

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Deadlock Property

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Livelock Property

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Find Flow

Is a given MSC included in a given HMSC?

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Find Flow

Is a given MSC included in a given HMSC?

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Universal Boundedness

What size of buffer is needed to be sure it will not overflow?

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Universal Boundedness

What size of buffer is needed to be sure it will not overflow? Every finite input buffer of Y can overflow.

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Universal Boundedness

What size of buffer is needed to be sure it will not overflow?

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Universal Boundedness

What size of buffer is needed to be sure it will not overflow? Buffers of size 1 will not overflow.

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Time Consistency

Are the given time conditions consistent?

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Time Tightening

Some time conditions can be tightened.

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Time Tightening

Some time conditions can be tightened.

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MSC - Summary

Basic MSC instances messages send events receive events conditions coregions general ordering inline expressions time constraints timers High-level MSC (HMSC) start node end node reference nodes connection points lines conditions time constraints

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MSC - Properties

Acyclic property FIFO property Race Condition Deadlock Livelock Find Flow Nonlocal Choice Universal Boundedness Existential Boundedness Time Race Condition Time Consistency Tighten Time

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MSC - Tools

IBM Rational, SanDriLa SDL, Cinderella SDL Sequence Chart Studio (SCStudio) MS Visio addon drawing, import, export checkers for all the mentioned properties MSCan academic tool

nly textual input

some checkers Mesa academic tool local choice and time checkers

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TCP Demonstration

known TCP diagram HMSC diagram detailed diagram

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Thanks for your attention

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