Architecture Definition & Analysis

1. Security Architecture and Analysis: Course Roadmap Session 1 (Linger) What: Methods for defining and reasoning about system architectures. Why: The architecture level is cost-effective and intellectually manageable for analysis and design of system security and survivability capabilities. Architecture Definition & Analysis Session 2, 3a (Linger) What: Survivability analysis improves preservation of critical mission capabilities. Why: No amount of security can guarantee that systems will not be compromised; essential services and assets must be maintained. Survivable Network Analysis Sessions 4, 6, 7. 9, 11 (Longstaff) What: Analysis of vulnerabilities and methods for improving system security. Why: System security can be improved by a variety of techniques at the network, operating system, and application level. Security Architectures Session 13 (Linger) What: Architecture development with COTS components Why: Most security vulnerabilities are the result of poor system development and acquisition practices. From a security perspective, good practices and management methods are critically important. Architecture Development Management • Plus: • Student team project in survivability analysis (Mead) • Guest lectures on special topics • Student presentations

2. Security Architecture and Analysis: Session 2a • Topics: • Session 1 Review • Architecture Life Cycle, Work Products, and Processes

3. Session 1 Review

4. REVIEW: Architecture Defined • An information system architecture • is a specification for development of a system • composed of hardware and softwarecomponents and connectors • whose external behavior satisfies the enterprise mission and • business requirements Enterprise mission and business requirements System operation Design Validate Design System architecture System development Validate

5. REVIEW: Concepts of System Architectures • Architectures are comprised of components and connectors: • Components (Computation) • Hardware: • Workstations, servers, mainframes, printers, sensors, actuators, … • Software: • Operating systems, data base systems, middleware, • browsers, applications, utilities, firewalls, ... • Connectors (Communication) • Hardware: • Communication links: routers, switches, public telephone • network, leased lines, virtual private networks, … • Software: • Communication protocols: TCP/IP, SNMP, HTTP, FTP …, Linkage • conventions: procedure calls, remote procedure calls, thread • initiation, ...

6. REVIEW: Concepts of System Architectures • Architecture properties: • Functional properties • Must satisfy domain-specific functional requirements • and specifications • Non-functional properties (the “ilities”) • Must satisfy performance, availability, reliability, safety, security, survivability, maintainability, usability, manageability, … properties • Architecture trade-offs: • Properties can conflict • Trade-offs seek optimal combinations of properties • based on cost/benefit analysis

7. REVIEW: Architectural Styles Example: A Bank ATM System Style: Hierarchical, client server, layered Users Domain/Enterprise Logic/ Data Layer Users Mainframe ... Infrastructure/ Communications Layer Server Server ... Server Presentation/User Interface Layer ATM ATM ATM ... ATM ATM ATM ATM ... ATM ATM ATM ATM ... ATM Users

8. REVIEW: Architectural Styles Gartner’s Two-Tier and Multi-Tier Enterprise Architectures: Plump Client Two Tiers Fat Client Two Tiers Thin Client Multi-tier Ultra-Thin Client Multi-tier Presentation Business Rules Data Access Presentation Business Rules Presentation Browser Desktop: Business Rules Data Access Business Rules Data Access DBMS Data Access DBMS Server(s): DBMS DBMS

9. REVIEW: Architecture Impact of COTS Products • Long history • Started with environment support • Operating systems, data bases, language processors, … • Moving up the food chain • Specialized applications, middleware, network services, ... • Most architectures today are “assembled” from COTS products • Domain-specific vendors • Bend business processes to match software capabilities • “Glue code” ties incompatible products together • COTS characteristics: • Ties your system capability and evolution to vendors • Cost savings possible, but risks must be managed • Functionality and security are what vendor says they are • Actual capabilities may differ • Source code usually not available • Knowledge of quality and reliability difficult to acquire • Acceptance testing and configuration management are critical

10. REVIEW: An Architecture Framework SYSTEM ARCHITECTURE Architecture Fundamentals: Architecture role and life cycle Architecture representation and reasoning Architecture processes and work products Architecture analysis and design Architecture modeling and validation Architecture patterns and properties COTS evaluation and integration Marketplace Environment: Partners and alliances COTS and component products Service and consultation offerings User groups and standards System Environment: enterprise architecture, business models, system usage and evolution Parts for Developing System Requirements: function, and properties of reliability, performance, scalability, security, usability, cost, … Ability to Develop External Behavior View (System Specification): User tasks and workflows Function and information Stimulus/response behavior Domain Architectures: EAI architectures E-commerce architectures Directory architectures System management architectures Middleware architectures Industry standard architectures Framework for Developing Architecture Best Practices: Enterprise modeling and requirements specification Application analysis and design Data analysis and design System integration Network analysis and design Incremental system development Data and Software View (Logical Infrastructure): Middleware and applications Databases and storage systems Operating systems Processes for Developing Enabling Technologies: Computing & comm. components Microsoft technologies JAVA technologies Web technologies XML technologies Security technologies Architecture patterns Development methods and tools Tools for Developing Hardware and Network View (Physical Infrastructure): Computing hardware: servers, mainframes, PCs,mass storage, … Networks, wired & wireless: media, devices, topology, protocols Client Environment: Client relations, people, and culture Enterprise architectures, business models, workflows, & legacy systems Functional, non-functional, & usage requirements and constraints Goals for Developing

11. REVIEW: Box Structure Reasoning for Components • Box Structures • A systematic model for component analysis and design • Five fundamental component characteristics: “BURST” • Boundary: What is inside and what is outside? • Users: Who are the users? • Responses: What is the set of possible responses? • Stimuli: What is the set of possible stimuli? • Transactions: What are the possible mappings from stimuli to responses? • Three fundamental component representations: • Black box: Component behavior based on history of use • State Box: Component behavior based on retained data • Clear box: Component behavior based on procedure (another course!)

12. REVIEW: Box Structure Reasoning for Components: Black Boxes • The black box of a component in diagram form Stimulus (S) Response (R) • The example of black box behavior: A hand calculator Stimulus history Stimulus Response 716 5 7165 716C 5 5 • Black box behavior depends on more than the current stimulus, • it also depends on the history of use • Transition function of a black box description • (stimulus history, stimulus)  (response)

13. REVIEW: Box Structure Reasoning for Components: State Boxes • The state box of a component in diagram form state Stimulus (S) Response (R) trans • Opens up a black box to reveal retained data; allows reasoning about • the state • Transition function of a state box description • (stimulus, current state) --> (response, new state)

14. REVIEW: Compositional Reasoning for Networks A Bank ATM System Domain/Enterprise Logic/ Data Layer Users Mainframe ... Infrastructure/ Communications Layer Server Server ... Server Presentation/User Interface Layer ATM ATM ATM ... ATM ATM ATM ATM ... ATM ATM ATM ATM ... ATM Users

15. REVIEW: Compositional Reasoning for Networks • What happens from viewpoint of ATM user submitting a transaction? User ATM Server Mainframe Server ATM User • [User] o [ATM] o [server] o [mainframe] o [server] o [ATM] o [User] • “o” is composition operator • “[, ]” denote the transition function of the component • Note that each use of a component is in the composition • Component compositions are also known as architecture traces • ATM Security: Composition with wrong pin number (U for user) U U U U U U U U ATM Server ATM Server ATM Server ATM Try again wrong pin Try again wrong pin Access denied

16. REVIEW: Compositional Reasoning for Networks • Another pin number composition U U U Server ATM right pin Access granted U U U U U U U U ATM Server ATM Server ATM Server ATM wrong pin Try again wrong pin Try again wrong pin Access denied • Compositional reasoning is concerned with the net effect of • all the components in a composition • Net effect means the overall change • From the stimuli to the first component • To the response from the last component

17. REVIEW: Compositional Reasoning for Networks When you buy gas at a pump with a speedpass, what is a possible architecture trace of your transaction? ? User pump pump User Despite the fact that thousands of users may be accessing the system at the same time, the system is designed to maintain the compositional integrity of the architecture traces of all the users. It appears to you as though you are the only user.

18. REVIEW: Compositional Reasoning for Networks A Bank ATM System Users Mainframe ... Server Server ... Server ATM ATM ATM ... ATM ATM ATM ATM ... ATM ATM ATM ATM ... ATM Users • Many systems are designed to preserve composition and isolate • asynchronous behavior • Bank system preserves independence of transactions based on • account numbers • In general, systems are designed for compositional operations

19. Architecture Life Cycle, Work Products, and Processes

20. Architecture Life Cycle: Inputs INPUTS Architecture Fundamentals Architecture Practices Client Environment: enterprise arch. legacy systems initial requirements Marketplace Environment Domain Architectures Enabling Technologies

21. Architecture Life Cycle: Inputs: Enterprise Architecture Def’n • If it exists and is current • May define business models • May define IT infrastructure • May define evolutionary objectives • May provide guidance for architecture development • If it exists and is not current • Opportunity to update • Guidance is suspect Perspective Know the status of enterprise architecture definition Analyze existing enterprise architecture IT infrastructure Evaluate requirements wrt existing infrastructure

22. Architecture Life Cycle: Inputs: Legacy systems • Legacy reuse and integration • Data, software, and networks involved • Potential major costs or savings • Impacts architecture, development, & deployment • Many alternatives possible • Wrapping, rewriting, transforming, rehosting, … • Decision making • Legacy systems are often difficult to modernize • Assessment of legacy capabilities is crucial • Business valuation of legacy assets is crucial • New uses for old data • Business case, cost/benefit analysis Perspective Analyze legacy capabilities wrt client requirements Understand evolution plans for legacy assets Treat legacy integration on a par with new components Architect for firm future uses of legacy elements

23. Architecture Life Cycle: Inputs: Initial Requirements • Often not fully known by client • Effective requirements discovery is essential • Enterprise and business models are the basis • Functional requirements • User tasks and workflows • System services and transactions • Use cases are a popular method • Usage requirements • User types and roles • Usage patterns and traffic levels • Non-functional (property) requirements • Reliability, performance, scalability, security, survivability, usability, cost, … Perspective Never architect against presumed requirements Avoid late-life-cycle requirements surprises Iterate requirements definition with clients Involve all client roles and stakeholders Treat requirements as an architecture entry condition Develop prototypes to elicit requirements from clients Establish requirements baselines to manage change and prevent scope creep

24. Architecture Life Cycle: Inputs: Marketplace Environment • Partners and alliances • Partnering can reduce costs and spread risk • COTS products • Extensive, comprehensive capabilities available • Vendor capability and track record can be issues • Product function and quality can be issues • Trend to standard, integrated solutions • User groups and standards • Provide experience benchmark, enable interoperability Perspective Capitalize on alliance strategies and agreements Perform due diligence assessments of vendors Evaluate function and quality of COTS products Reconcile COTS capabilities with client requirements Recognize COTS selections tie clients to supply chains Capitalize on accepted standards, avoid others

25. Architecture Life Cycle: Inputs: Domain Architectures • EAI architectures • Data-, application-, portal-, process-oriented, … • XML, middleware, RPCs, message brokers, … • Packages: SAP, PeopleSoft, BizTalk, … • E-commerce architectures • B2C, B2B, B2G, G2C… • Content, payments, orders, fulfillment, … • Security, trust, privacy, QoS… • Packages, ISPs, … • Industry standard architectures Perspective Capitalize on applicable domain architectures Maintain knowledge of evolving domain methods

26. Architecture Life Cycle: Inputs: Enabling Technologies • Computation & communication hardware • Processing power and bandwidth • Intel, Cisco, … • Hardware in continual evolution • Integration environments • Applications, middleware, operating systems, … • Microsoft, Sun, Oracle, … • Environments in continual evolution • Integration enablers • HTML, XML, security, … • Enablers in continual evolution Perspective Maintain knowledge of evolving technologies Where possible, build on existing client environments Recognize enabler selections tie clients to supply chains Architect for component and environment evolution

27. Architecture Life Cycle: Work Products INPUTS WORK PRODUCTS Architecture Fundamentals Architecture Practices Client Environment: enterprise arch. legacy systems initial requirements Marketplace Environment Domain Architectures Enabling Technologies Final Requirements Prototypes & Models Architecture Design Architecture Provisioning Architecture Validation Vendor Agreements Development Plan

28. Architecture Life Cycle: Work Products: Final Requirements • Discovery and reconciliation • Requirements analysis with client • User experience with prototypes • User needs vs. product capabilities • Requirements trade-offs • Optimal non-functional property mix • Functional trade-offs: • Goal is no project impact • Customer understands trade-offs • Customer agrees to requirements baseline • Schedule and budget remain intact Benefit Low High Discuss High No Go Perspective Challenge and confirm key requirements Find any under-represented stakeholders Review property trade-offs with client The baseline plus controlled changes are the final reqs. It doesn’t matter how well the wrong system is built Cost Discuss Go Low

29. Architecture Life Cycle: Work Products: Prototypes & Models • Prototype goals • Requirements elicitation and finalization • Proof of concept • Model goals • Simulation, prediction of system performance • Proof of concept • Prototyping and Modeling • Key risk management strategies • Can be a phase in multi-phase project Perspective Target prototypes to specific questions and objectives Evolving prototypes into products can be very risky Model results are only as good as model fidelity Model results are only as good as model inputs Match modeling effort to project stakes

30. Architecture Life Cycle: Work Products: Architecture Design I • Architecture is the integrating foundation of the project • A complete abstraction of the final system • Defers details without losing them • Development and usage become envisionable • Basis for reasoning, discussions, and decisions • Satisfies client needs • Functional and non-functional requirements • Traceability of requirements into architecture is important • Prescribes system development • Architecture should leave nothing out at its level of abstraction • Development should refine, not invent, architecture Perspective Get all the guidance, advice, and review you can find Simple and straightforward solutions are best Use what is known to work -- capitalize on similar projects

31. Architecture Life Cycle: Work Products: Architecture Design II • Architecture defines • External behavior design (system specification) • User tasks and workflows • Stimulus/response behavior • Data and software design (logical infrastructure) • Retained state, application software, … • Middleware, operating systems, databases, … • Partitioning of function and data in an architectural style • Hardware and network design (physical infrastructure) • Servers, mainframes, PCs, … • Media, devices, topology, protocols, … • Non-functional properties • Property definitions • How properties are satisfied • User skills and training

32. Architecture Life Cycle: Work Products: Provisioning • Provide specifications for every component • Function • Usage • Non-functional properties • Provide source for every component • As-is or modified legacy or COTS • As-is or modified partner product • Enabling environment or technology • New development • ISP, ASP, … • Various combinations Perspective Select sources based on component specifications Satisfy cost objectives Define level of effort for component provisioning Carefully weigh benefits of buy vs. build Develop components as a last resort

33. Architecture Life Cycle: Work Products: Validation • Validate architecture functionality • Every required user function must be present • All functions must operate harmoniously • Validate non-functional properties • Every required property must be satisfied • All properties must co-exist harmoniously • Validation processes • Verify “as-designed” against “as-specified” • Many methods may be employed • Team inspections are a key technique Perspective Treat validation as a distinct task Apply validation entry and exit conditions Ensure artifacts are in shape for validation Validate conformance of artifacts to specifications Document evidence for conformance Iterate validation and rework until artifacts pass Use validation defect rates to manage quality

34. Architecture Life Cycle: Work Products: Vendor Agreements • Architecture is a driver of vendor agreements • Incorporates vendor components • Basis for development plan • Defines component deliverables • Provisioning strategies • Requirements and specifications • Defines service deliverables • Scope and QoS • Staffing and skills Perspective Define deliverables for vendor agreements Perform due diligence on vendor capabilities Define checkpoints for assessing vendor progress Define testable acceptance criteria for deliverables Define implications of acceptance failure Manage risk with plan B for critical components

35. Architecture Life Cycle: Work Products: Development Plan • Defines development environment • Enabling technologies • Development and testing processes • Defines development steps • Incremental development is essential • Stepwise completion of system parts • Client feedback from early increments • Tasks and schedules Perspective Define environment early to drive staffing and training Define steps so that system accumulates into final form Be prepared for development feedback to architecture Evaluate early increments wrt required properties

36. Architecture Life Cycle: Arch. Development INPUTS ITERATIVE ARCHITECTURE DEVELOPMENT WORK PRODUCTS Architecture Fundamentals Architecture Practices Client Environment: enterprise arch. legacy systems initial requirements Marketplace Environment Domain Architectures Enabling Technologies Planning Mgmt. Plan Final Requirements Prototypes & Models Architecture Design Architecture Provisioning Architecture Validation Vendor Agreements Development Plan Ent. Arch., Legacy, Reqs., Market, Domain, Enablers Analysis (Architecture Development) Devel. Planning Env. and Steps Schedule

37. Architecture Life Cycle: Arch. Development: Schedule • Embedded within project schedule • Supports project dependencies • Entry conditions (rarely satisfied) • Stable and complete requirements • Availability of appropriate staff and resources • Exit condition • Architecture work products are complete and validated Perspective Failure to meet schedule is a non-starter Surface schedule-impacting problems early Work at level of abstraction compatible with schedule

38. Architecture Life Cycle: Arch. Development: Management Plan • Defines work products • Project-specific architecture artifacts • Defines tasks • Activities that will produce the work products • Defines internal schedules and resources • Task sequencing and resource allocation • Defines risks and mitigations • Key risks and uncertainties • Actions for recognition and control Perspective Plan is a sequencing of tasks plus risk management Define tasks to accumulate into work products Use the plan to manage the architecture work Track actual vs. predicted performance Discovery/experimentation tasks can reduce risk

39. Architecture Life Cycle: Arch. Development: Analysis • Understand the client and resources • Client problem • Enterprise architecture and business models • Legacy systems • Requirements • From present operations to envisioned future operations • Potential resources • Marketplace offerings • Domain architectures • Enabling technologies • A project-long activity • May require experimentation, training • Document understandings for decision-making Perspective Never stop learning about the problem and resources

40. Architecture Life Cycle: Arch. Development: Development Planning • Define development environment • Define development and testing steps Perspective Consult with developers to arrive at a consensus plan Consult with customers on staging of deliverables

41. Architecture Life Cycle: Arch. Development: Design Activities INPUTS ITERATIVE ARCHITECTURE DEVELOPMENT WORK PRODUCTS Architecture Fundamentals Architecture Practices Client Environment: enterprise arch. legacy systems initial requirements Marketplace Environment Domain Architectures Enabling Technologies Planning Mgmt. Plan Final Requirements Prototypes & Models Architecture Design Architecture Provisioning Architecture Validation Vendor Agreements Development Plan Ent. Arch., Legacy, Reqs., Market, Domain, Enablers Analysis External Behavior Iterations Design Refine Refine Data & Software Design Refine … Hardware & Network Design Validation Checkpoint Inspection Devel. Planning Env. and Steps Schedule

42. Architecture Life Cycle: Arch. Development: The Refinement Process • External behavior design maps requirements into specifications • External behavior design plus network traffic, etc., drives data and software design • Data and software design plus network traffic, geography, etc., drives hardware and network design • Non-functional requirements drive everything • System evolution requirements drive everything Perspective Refinement process allows divide, connect, and conquer strategy Refinement helps maintain intellectual control Refinements can be verified wrt their specifications Can’t design the top without knowing the bottom Last intellectual pass is top down

43. Architecture Life Cycle: Arch: Development: The Iteration Process • The first idea is rarely the best idea • Iteration drives evaluation and improvement • Iteration permits systematic convergence to a solution • Iteration has desirable properties similar to requirements change control • Iterations document design decisions Perspective Use iteration to achieve informed agreement Use iteration to uncover gaps and misunderstandings Continually challenge assumptions and decisions