The Architecture of Distributed Systems

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The Architecture of Distributed Systems

• Enterprise wide computing, networking and the
  desktop revolution

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IT Architecture

• Hardware and software
• Tools to access, package, deliver, communicate
  information
• Standards, models, control framework
• Configuration integrating components
• What is the difference between an IT Architecture
  and an IT Infrastructure?

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IT Architecture and Infrastructure

• Architecture is overall blue print of how systems
  fit together
• IS community has lost credibility b/c of failure
  in this area.
• Infrastructure is a particular implementation of
  IT architecture with basic capabilities shared
  across business units.
• ??Why is an overall IT architecture important?

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Views of IT Infrastructure

• Utility
• necessary and unavoidable service, often viewed
  as administrative expense.
• Firms with this view tend to offer fewest
  infrastructure services
• focus on lowering costs and not reengineering
  processes.

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Views of IT Infrastructure

• Dependent
• Tied to specific business programs in plan (ex.
  Improve service quality)
• infrastructure planning included in current
  business plan
• measured in short-term benefits
• minimum requirement for implementing BPR

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Views of IT Infrastructure

• Enabling
• continuous re-alignment of IT infrastructure with
  firm strategy.
• Long term strategy
• infrastructure provides basis for flexibility,
  rapid adaptation of future strategies
• costs viewed as business investments
• networks used extensively in business processes
• increased up front costs

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Focus on IT Infrastructure

• Corp. IS departments moving from hw/sw to
  application/infrastructure focus
• IS depts. in business of maintaining IT
  infrastructure
• s/w development reduced to modifying packages
  for/by end users
• CIOs starting to prefer CTO title
• Why is IS dept. focus on infrastr. a recipe for
  obsolescence or extinction of IS depts.?

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IT Architecture

• Applications
• IT-enabled process redesign
• Productivity applications
• Competitive advantage
• Structure controls
• Standards, policies and procedures
• Information models
• System development methodologies

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IT Architecture

• User interface
• GUI
• IO devices
• Tools packages
• Presentation reporting
• Analysis modeling
• Groupware
• Personal productivity
• DSS

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IT Architecture

• Information Management
• Hardware
• OS
• DBMS
• Document management systems
• Information retrieval
• Communication management
• Networks
• Gateways
• Email file transfer

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IT Architecture Evolution

• Mainframes with dumb terminals
• download/upload data
• run mainframe programs (usu. batch)
• little local processing
• Micros moved it to desktop
• Network computing model
• centralized model with network replacing m/f

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The Computer System Concept
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Changes in Computer Architecture
1930
1950
1957
1965
1975
firstgeneration
secondgeneration
thirdgeneration
fourthgeneration
prototype
vacuumtube
transistor
integratedcircut
mechanicalrelay
microprocessor
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Pentium Chip
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A Microprocessor
control unit
arithmeticlogic unit
128K temporary memory
input/outputcircuitry
systemclock
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Performance vs. Price
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Computer Classifications
Mainframes
Midrange Computers
Microcomputers
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Networked Computer Systems
Host Systems/ Superservers
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How distributed are your systems?

• Where is the processing of data done?
• Distributed processing
• How are the processors and other devices
  interconnected?
• Processor connectivity
• Where is the information stored?
• Distributed databases
• What rules or standards are used?
• Protocols, transmission standards, etc.

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Distributed System Frameworks

• Organizational View
• Corporate HQ
• Regional HQ
• Plant or Site
• Department
• Work Group
• Individual

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Types of Distributed Systems

• Host-based hierarchical systems

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Host-based Hierarchy
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Types of Distributed Systems

• Host-based hierarchical systems
• Decentralized Stand-Alone Systems

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Decentralized Stand-alone System
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Types of Distributed Systems

• Host-based hierarchical systems
• Decentralized Stand-Alone Systems
• Peer-Peer LAN-Based Systems

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Peer-to-Peer LAN-based System
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Types of Distributed Systems

• Host-based hierarchical systems
• Decentralized Stand-Alone Systems
• Peer-Peer LAN-Based Systems
• Hybrid Enterprise-Wide Systems

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Types of Distributed Systems

• Host-based hierarchical systems
• Decentralized Stand-Alone Systems
• Peer-Peer LAN-Based Systems
• Hybrid Enterprise-Wide Systems
• Client/Server Systems

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Some Common Client/Server Definitions

• A network that uses smart nodes instead of dumb
  terminals
• Ability to distribute the workload
• Client manages the human interface server
  manages the files

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Client/Server Basic Architecture
Request Sent
Request Answered
Client
Server
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Client/Server Basic Architecture
Server
Client
Server Becomes
Client
Mainframe
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Types of Servers

• Database Servers
• Resource Servers
• Application Servers
• Computation Servers

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Client/Server Computing (from Gartner Group 5)
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Benefits of Client/Server Computing

• Easy Database Access
• Downsizing Computer Resources
• Shared Hardware Software Resources
• Increased Management Control
• Remove Islands of Automation
• Scalable Architecture

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Benefits of Client/Server Computing

• Faster Application Development
• Reduced Application Development Backlog
• Increased Application Performance

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Barriers to Client/Server Computing

• Implementation Costs
• Equipment
• Systems Integration
• Retraining IS Personnel
• MIS Culture
• Immature Technology
• Lack of Management Tools

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Barriers to Client/Server Computing

• Threat to Stable Operations
• Data Security
• Complexity
• Investment Payback

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Types of Distributed Systems

• Host-based hierarchical systems
• Decentralized Stand-Alone Systems
• Peer-Peer LAN-Based Systems
• Hybrid Enterprise-Wide Systems
• Client/Server Systems
• Network-Centric Systems
• NC machines (see table 6-3 for summary costs)

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Network-Centric System
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Enterprise IT Architecture

• Enterprise architecture framework
• Account for different roles in complex projects
• planner, owner, designer, builder, sub, user
• Account for components of complex systems
• data models, functional models, network models,
  people, time frames, underlying goals/motivations
• usually requires huge investment and corporate
  wide initiative

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Assimilating New IT

• Phased Assimilation Model
• Technology Identification
• Learning and Adaptation
• Rationalization/Management Control
• Maturity/Technology Transfer

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Types of IT Investments

• strategic system investments
• Informational system investments
• EIS, DSS, management control, etc.
• Transactional system investments
• support repetitive, operational processes
• Infrastructure investments
• provide the base foundation of IT capabilities

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Types of IT Investments
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Conclusions

• Distributed systems have dominated IT development
  of 1990s architectures
• C/S type may be moving to hybrid NC type
• No one predicted the rise of the Internet
• Internet2?
• Complexity and speed of distributed systems will
  increase