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Solving InterOperability Problems Using Object-Oriented CSP Modeling

Solving InterOperability Problems Using Object-Oriented CSP Modeling. Mohammed H. Sqalli Eugene C. Freuder University of New Hampshire msqalli,ecf@cs.unh.edu. -The first author is currently at the of Canada Ltd.

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Solving InterOperability Problems Using Object-Oriented CSP Modeling

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  1. Solving InterOperability Problems UsingObject-Oriented CSP Modeling Mohammed H. Sqalli Eugene C. Freuder University of New Hampshire msqalli,ecf@cs.unh.edu -The first author is currently at the of Canada Ltd. -This material is based in part on work supported by the National Science Foundation.

  2. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  3. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  4. Specifications (What should Happen) Device B Device A Observations (What really happens) InterOperability Testing Communication line InterOperability Testing <=> Compare (Specifications, Observations) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  5. Example from a Test Suite • Test Case ID: V4202H__004 • Test Purpose: Verify that the first Hello sent from both sides contains Remote node ID and Remote port ID set to zero (1Way). • Pre-requisite: Both SUTs (A, B) are in different lowest level peer groups(Out). • Verdict Criteria: The first Hello packet observed from each SUT will have the Remote node ID field and Remote port ID field set to zero(1WayOut). IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  6. 1WayOut 1WayOut Example - Test Description Switch A Switch B IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  7. 1WayOut(A) {Source, Time, Status, Node_ID, ...} 1WayOut(B) {Source, Time, Status, Node_ID, ...} ... Variables 1WayOut(A).Status = Mandatory 1WayOut(A).Remote_Node_ID != 0 Unary Constraints 1WayOut(A).Time < 1WayOut(B).Time 1WayOut(A).Peer_Group_ID != 1WayOut(B).Peer_Group_ID ... Binary Example - CSP Model 1WayOut(A) 1WayOut(B) < Status Type Time Status Type Time 1 1 Hello Hello != Port ID Node ID Source Port ID Node ID Source Peer Group ID Peer Group ID != Remote Port ID Remote Node ID Remote Port ID Remote Node ID 0 0 0 0 IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  8. Panel showing the CSP model of a test case Panel for declaring variables and domains Panel for declaring constraints ADIOP Modeling - Test Suite Builder GUI IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  9. ADIOP Diagnosis - Test Suite Menu GUI IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  10. Test Suites CSP #2 Test #1 Test #2 CSP #1 Protocol Specification Monitored Observations … Decoded Observations CSP Models … ADIOP – The big picture (Four modules) Decoding Modeling Update Diagnosis Result Debugging OK ? Store Next Step CBR + Expert Result Report Yes No IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  11. Test Suites Test #2 Test #1 CSP #2 CSP #1 Protocol Specification Monitored Observations … Decoded Observations CSP Models … ADIOP – Modeling & Diagnosis Decoding Modeling Diagnosis Result IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  12. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  13. InterOperability Lab • Verify the interoperability and/or conformance of the computer communications products • Consortiums: ATM, FDDI, Wireless, … • Protocols tested: UNI, LANE, PNNI, … • Test Suites for IOP testing: LANE, PNNI, … • Testing Equipment: Snifters, Generators,... • Testing Problems: Data Analysis, Similar Problems, ... IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  14. ATM and PNNI • Asynchronous Transfer Mode • supports all classes of traffic: voice, video, and data • provides quick and easy switching and multiplexing • connection oriented • Private Network Network Interface • provides dynamic routing: includes discovery of the topology of the network • supports QoS and hierarchical routing • scales to very large networks IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  15. Protocol Specifications Observations Compare to Report InterOperability Testing Network Device B Device A Monitor IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  16. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  17. Motivations – The ADIOP System • Model IOP test cases efficiently. • Diagnose IOP problems in a timely manner • Analyze a large amount of data • Provide an explanation of the diagnosis • Keep trace of previous problems and their solutions to be reused in future similar cases • Debug IOP tests IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  18. Solution - The ADIOP System • Automate the process of InterOperability Testing • CSP modeling of IOP tests • Diagnosing IOP problems quickly and efficiently using CSP models (including Explanation) • Repeatability of testing • Reusable diagnosis and results: experience is kept • Explanation and Reports generation • Debug the InterOperability tests IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  19. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  20. X X: red Y: blue Z: green Red green blue • Search • Inference Red green blue Red green blue Y Z X Y Z Variables CSP Algorithm Solution CSP Representation Constraint Satisfaction Problems X Y Z Coloring Problem Problem Statement Values Constraints IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  21. Test Suites Test #1 Test #2 CSP #1 CSP #2 Protocol Specification Monitored Observations … Decoded Observations CSP Models … Result CSP Modeling and Diagnosis of InterOperability Testing NB: The decoders have built in functionality that provides the information (protocols, packets, packet’s fields) to build the CSP models. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  22. Modeling with objects • An IAAI-01 presentation on August 7, 2001 at 10AM entitled: “Constraint-Based Modeling of InterOperability Problems Using an Object-Oriented Approach” will provide more details on the OO-based CSP modeling of ADIOP. • One-Model vs. Many-models architectures • Modeling with Objects • Test cases as objects • Advantages of CSP modeling using OOP • Modeling language definition IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  23. Modeling Interface (GUI) Protocols List: loaded from the class hierarchy of the Packet class Packet Types List: loaded from the class hierarchy of the protocol’s class Packet’s Parameters (CSP variables) List: loaded from the class definition of a packet. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  24. Test Suite Builder GUI Step 1: Choose the protocol Step 2: Start CSP Model Step 3: Define the packets Step 4: Define the constraints Step 5: This generates the test case object IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  25. Example of CSP Modeling- Modeling Language - $CSP $PROTOCOL PnniRout $PACKET OneWayOutA Hello $PACKET OneWayOutB Hello $UNARY_CONSTRAINT OneWayOutA.status D_Mandatory $UNARY_CONSTRAINT OneWayOutA.remote_port_id == 0 $UNARY_CONSTRAINT OneWayOutB.remote_port_id == 0 $UNARY_CONSTRAINT OneWayOutA.remote_node_id == 0 $UNARY_CONSTRAINT OneWayOutB.remote_node_id == 0 $BINARY_CONSTRAINT OneWayOutA.time < OneWayOutB.time $BINARY_CONSTRAINT OneWayOutA.source != OneWayOutB.source $BINARY_CONSTRAINT OneWayOutA.peer_group_id != OneWayOutB.peer_group_id $ENDCSP Protocol Metavariables Optional statement Unary Constraints Binary Constraints IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  26. Test Suite Menu (GUI) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  27. Test Suite Directory Hierarchy adiop adiopx testsuite pnnirout lane mpoa V4301H_002 V4301H_003 V4301H_001 • Test cases are stored in the appropriate directory. • Menu of test cases is generated dynamically from this directory structure. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  28. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  29. Constraint-Based Diagnosis of IOP Problems • Diagnosis of Interoperability problems is the detection of problems that occur when two devices running the same networking protocol are connected to each other through a network. The devices are assumed to have passed conformance testing which states that each device by itself is conformant in its behavior to the protocol specification. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  30. Test Suites Test #2 CSP #2 CSP #1 Test #1 Protocol Specification Monitored Observations … Decoded Observations CSP Models … ADIOP – Modeling & Diagnosis Decoding Modeling Diagnosis Result Builds CSP models for test cases [Metavariables/ Constraints] Generates decoded observations [Metavalues] Compares decoded observations to CSP model IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  31. Algorithms for Diagnosis • CSP is used for modeling IOP test cases  Use CSP for diagnosis and take advantage of the already existing algorithms for solving CSPs. • Main goal of diagnosis: to get a “good” explanation of the problems. • Algorithms: search supplied by consistency inference methods in a CSP context. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  32. Search • Simple backtracking adapted to OO-based CSPs. It uses metavariables and metavalues. • Search for the first solution if it exists. • Explanation provided to testers: • Test passes: which packets constitute the solution (useful to testers) • Test fails: solution obtained is not very useful to testers IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  33. Inference and Consistency Checking • Get a better explanation in case of failure of a test case • Specialized Node Consistency inference for and OO-based CSP [MVC]. • Domains of all metavariables are set to all observed packets. • Use some variables to reduce the domain of metavalues for metavariables: protocol and packetType variables. • If no packet observed belongs to the protocol in the CSP model, then there is no solution. • Delete all metavalues that do not appear in the CSP model as one of the metavariables types (packetType). • If size of a domain shared by n metavariables is reduced to r with r < n, then there is no possible solution (overconstrained n-clique) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  34. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  35. Explanation • ADIOP uses templates to generate human-like explanations. • Example: There are less observed packets of type packetType than what is stated in the model of this test. • Used when there is an overconstrained clique. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  36. Reports generation • Individual test case reports • Section test cases reports IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  37. Evaluation • 4 real-world observations: 3 from the PNNI Routing protocol and 1 from the LANE protocol. • Run only test cases that belong to the protocol used when the observations were captured. • Compare time and explanation when using preprocessing (inference) + backtracking vs. backtracking only. • Preprocessing lead to a reduction of time effort needed for solving the problems and produced a better explanation. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  38. Evaluation - Summary • Out of 69 test cases run: • 36 passed  useful explanation • 33 failed: • 14 using only preprocessing  useful explanation • Total of 50 test cases produces a useful explanation (73%) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  39. Complexity • s: size of the domains of metavalues. • r: reduced size of s after preprocessing (r ≤ s) • n: number of metavariables defined in a model • Backtracking: O(sn) • Preprocessing: O(n2s) • Preprocessing + Backtracking: O(rn) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  40. Outline • Example • Domain of Application • Motivations and Contributions • CSP Modeling • Constraint-Based Diagnosis • Explanation & Evaluation • Summary IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  41. Test Suites CSP #2 Test #1 Test #2 CSP #1 Protocol Specification Monitored Observations … Decoded Observations CSP Models … ADIOP – The big picture (Four modules) Decoding Modeling Update Diagnosis Result Debugging OK ? Store Next Step CBR + Expert Result Report Yes No IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  42. Test Suite Builder Decoder Diagnoser Test Generation and Implementation Test Debugger Decoder s Builder Decoder Usage Test Execution (Algorithms) Menus and Reports Test Description from IOP test suite CSP Model Protocol Specification Hierarchy of Classes Search (hard explanation) Automate Menus Creation CBR + User Interaction Natural Language Processing Frame Format (Defined language) Packet Inference (better explanation) Reports Generation Correct/Update CSP Model PnniR MPOA Graphical Representation Java file (Frame decoder) Notes: Existent Documents Hello DBS New CSP Model CSP Model Java Class (Frame decoder) Implemented Note: These classes are used by Decoder, Diagnoser, and Test Builder. Java file To be implemented Java Class (used by diagnoser) Not implemented ADIOP (Automated Diagnosis of InterOperability Problems) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  43. Summary • CSP Model building: Simple, declarative, transparent, GUI-based, and complete modeling language for stating and generating IOP tests. • OO provides a more natural, concise, scalable and reusable framework for model statement of IOP tests (+ Inheritance, Encapsulation) • Combination of CSP and OO: metavariables and metavalues to represent packets and generate test cases as objects. • Scalability: More protocols can be made available for modeling by adding the corresponding decoders. • Modeling Interface: dynamic loading of protocols and packets being used. • Modeling Language: • Generic across protocols: Independent of the protocol being used. • Constraint expressiveness: unary and binary constraints. • Many-models architecture: test suites are used instead of protocol specifications. Each test case is represented by a CSP model. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  44. Summary (Cont.) • The test cases built using the ADIOP’s modeling component are dynamically accessible through a menu. • Motivations of Diagnosis of IOP Problems: save time, reduce repetitive testing, store and reuse knowledge, automate reports generation. • Advantages of using CSP for modeling and diagnosis: take advantage of existing CSP algorithms. • Algorithms for Diagnosis: Search and Inference. • Generate an accurate and human-like explanation. • Explanation & Evaluation: Diagnosis and Explanation of IOP problems. • Evaluation and summary numbers: 50 (73% ) test cases out of 69 built produced a meaningful explanation. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  45. Constraint-Based Modeling of InterOperability Problems Using an Object-Oriented Approach Mohammed H. Sqalli Eugene C. Freuder University of New Hampshire msqalli,ecf@cs.unh.edu Discussion

  46. Contributions • Model building: Simple, declarative, transparent, GUI-based, and complete modeling language for stating and generating IOP tests. • OO provides a more natural, concise, scalable and reusable framework for model statement of IOP tests. • Combination of CSP and OO: metavariables and metavalues to represent packets and generate test cases as objects. • Modeling is generic across protocols: independent of the protocol being used. • Scalability: More protocols can be made available for modeling by adding the corresponding decoders. • Dynamic loading of protocols and packets being used. • Many-models architecture: each test case is represented by a CSP model. • Use of test suite instead of protocol specification. • Constraint expressiveness: unary and binary constraints. • CSP algorithms for diagnosing IOP problems: search and specialized inference consistency methods. • Provide an explanation of the cause of IOP problems. IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

  47. Specifications (What should Happen) Device B Device A Observations (What really happens) InterOperability Testing Communication line InterOperability Testing <=> Compare (Specifications, Observations) IJCAI-01 Workshop - CONS-1: Sqalli & Freuder

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