The Design of System Architecture

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The Design of System Architecture
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System Architecture

• System architecture translates the logical design
  of an information system onto a physical
  structure includes hardware, software, network
  support, processing methods, and security.

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Deployment Environment

• Deployment environment definition bridges
  analysis and design
• Hardware
• System software
• Networking
• Common deployment environments in which system
  will operate
• Related design patterns and architectures for
  application software

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Single-Computer and Multitier Architecture

• Single-computer architecture
• Mainframe-based
• Limited by single machine capacity
• Clustered and multi-computer architecture
• Group of computers to provide processing and data
  storage capacity
• Cluster acts as a single system
• Multicomputer hardware/OS can be less similar
  than clustered

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Single-, Clustered, and Multicomputer
Architectures
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Centralized and Distributed Architecture

• Distributes system across several computers and
  locations
• Relies on communication networks for geographic
  connectivity
• Client/server architecture dominant model for
  distributed computing

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Application Architecture

• Complex hardware/networks require more complex
  software architectures
• There are commonly used approaches (patterns)
  for application architecture
• Client/server architecture
• Three-layer client/server architecture
• Web services architecture
• Internet and Web-based application architecture

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Client/Server Computing

• Information processing is distributed among
  several workstations and servers on a network,
  with each function being assigned to the
  environment that is best suited to perform it.
  The client initiates the requests and the server
  responds.
• Consolidate the virtues of traditional
  time-shared mainframe and mini-computer paradigms
  with the advantages of personal computers,
  workstations, and local area networks

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Components of Client/Server Computing

• Three interrelated componentsClient - the
  front-endServer - the back-endNetwork - the
  middle ware
• Many to many relationship between clients and
  servers.

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Client/Server Architecture

• Client/server divides programs into two types
• Server manages information system resources or
  provides well-defined services for client
• Client communicates with server to request
  resources or services
• Advantage deployment flexibility
• Location, scalability, maintainability
• Disadvantage complexity
• Performance, security, and reliability

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Interaction Among Multiple Clients and a Single
Server
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Client/Server Architectural Process

• Decompose application into client and server
  programs, modules, or objects
• Identify resources or services that can be
  centrally managed by independent software units
• Determine which clients and servers will execute
  on which computer systems
• Describe communication protocols and networks
  that connect clients and servers

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Three-Layer Client/Server Architecture

• Layers can reside on one processor or be
  distributed to multiple processors
• View layer accepts user input and formats and
  displays processing results
• Business logic layer implements rules and
  procedures of business processing
• Data layer manages access to stored data in
  databases

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Three-Layer Architecture
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Client/Server Tiers and Middleware

• Two-tier design client - server
• Three-tier design
• client application server data server
• Middleware
• Special utility software that enables the tiers
  to communicate and pass data back and forth.
• A transparent interface that enables system
  designers to integrate dissimilar software and
  hardware.

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Three-tier Client/Server System
Figure 1. Three-tiered client/server
architecture
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Client/Server Advantages

• Provide scalability, portability, and
  interoperability through standard-based openness
• Respond to the organizations need for easy
  information access, flexibility, smooth
  administration, reliability, security and
  proficient application development
• Mix, match, and combine diverse data elements
  located in different, often incompatible systems

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Client/Server Disadvantages

• Acceleration of complexity
• High hidden costsTechnical support costEnd-user
  operations costAdministration cost

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Web Services Architecture

• A client/server architecture
• Packages software functionality into server
  processes (services)
• Makes services available to applications via Web
  protocols
• Web services are available to internal and
  external applications
• Developers can assemble an application using
  existing Web services

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Web Services Architecture
WSDL Web Service Description Language UDDI
Universal Description, Discovery and Integration
SOAP 'Simple Object Access Protocol XML
Extensible Markup Language
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Internet and Web-Based Application Architecture

• Web is complex example of client/server
  architecture
• Can use Web protocols and browsers as application
  interfaces
• Benefits
• Accessibility
• Low-cost communication
• Widely implemented standards

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Multi-tiered Web Service System
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Negative Aspects of Internet Application Delivery

• Breaches of security
• Fluctuating reliability of network throughput
• Throughput can be limited
• Volatile, changing standards

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The Design of Communication Networks
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Networks

• Network - A set of interconnected devices that
  share a directory and can thus access each other
• The directory provides an address for each
  component of the network
• If the device is not included in the directory,
  it is not part of the network

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Components of a Network

• Terminals and workstations
• Transmission links
• Transmission methods
• Nodes and switches
• Network architecture and standards

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The layered protocol system concept
receive a letter
Application
Application
send a letter
logical link
mail sorting
mail sorting
Network
Network
mail unpacking and checking
mail packaging
Data link
Data link
physical link
Physical
Physical
transportation
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Layered Architecture

• Clear division of functionality gives modular
  approach to development and ease of
  standardization.
• Application independence - software assumes that
  services are available - no need to know about
  implementation details.
• Facilitates maintenance - can replace/omit or
  nominally implement a layer

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Classification of Networks

• By technology used cable, wireless,
• By topology ring, bus, star
• By geographic scope LAN, WAN, MAN
• By type of ownership Public, Private, VPN

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Computer Network

• Set of transmission lines, specialized hardware,
  and communication protocols
• Enables communication among different users and
  computer systems
• Local area network (LAN) less than one kilometer
  long connects computers within single building
• Wide area network (WAN) over one kilometer long
  implies much greater, global, distances
• Router directs information within network

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A Possible Network Configuration for RMO
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McMaster Campus Networks
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The Internet, Intranets, and Extranets

• Internet global collection of networks that use
  TCP/IP networking protocols
• Intranets
• Private networks using same TCP/IP protocols as
  the Internet
• Limited to internal users
• Extranets
• Intranets that have been extended outside the
  organization

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Identify the business criteria for the
telecommunications platform

• Translate business to technology along three
  dimensions of business functionality
• Reach the locations/people/organizations to
  which we must link
• Range the variety of information and
  transactions we must be able to share
• Responsiveness the level of service we
  guarantees, in terms of speed, reliability, and
  security

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Reach

• Levels of Reach
• Within a single location
• Across a firms domestic locations
• Across international locations
• To customers and supplies with the same
  technology base as the firms
• To all customers and suppliers
• To anyone, anywhere
• Connection is not communication

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Range

• Range involves the information and transactions
  that must be shared across business functions and
  processes
• Levels of Range
• Simple messages
• Access to separate data stores
• Independent transactions
• Cooperative transactions
• Object-oriented thinking

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Responsiveness

• Refers to the level of service we must guarantee,
  in terms of speed, reliability, and security
• Levels of responsiveness
• Non-immediate response - need not be on-line
• Immediate response - on-line during office hours
  - airline
• On-demand service - 24 hours a day - police
• Perfect service - always work with high security
  - defense

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Network Design

• Integrate network needs of new system into
  existing network infrastructure
• Describe processing activity and network
  connectivity at each system location
• Describe communications protocols and middleware
  that connects layers
• Ensure that network capacity is sufficient
• Data size per access type and average
• Peak number of access per minute or hour

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Network Diagram for RMO Customer Support System