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Presentation6 Presentation Transcript

  • 1. IE 20303
  • 2. What is Client/Server?
    Client
    Server
    Network
    How is client/server different from other distributed computing?
    Heavy reliance on user-friendly applications
    Emphasis on centralizing databases and management functions
    Commitment to openness/modularity
    Networking fundamental to operation
  • 3. Client/Server Terminology
    Application Programming Interface (API): A set of function and call programs that allow clients and servers to intercommunicate.
    Client: A networked information requester (usually a PC or workstation) that can query a database and/or other information from a server.
    Middleware: A set of drivers, APIs, or other software that improves connectivity between a client application and a server.
    Relational Database: A database in which information access is limited to the selection of rows that satisfy all search criteria.
    Server: A computer, usually a high-powered workstation or a mainframe, that houses information for manipulation by networked clients.
    Structured Query Language (SQL): A language developed by IBM and standardized by ANSI for addressing, creating, updating, or querying relational databases.
  • 4. Client-Server Environment
  • 5. Why is Client-Server Different?
    Emphasis on user-friendly client applications
    Focus on access to centralized databases
    Commitment to open and modular applications
    Networking is fundamental to the organization
  • 6. Client/Server Applications
    Emphasis on GUI for users
    Database Example
    Database on server, applications for access on client, “glue” (like SQL) enables requests)
    Application logic can be client-only, or split between client and server
  • 7. Classes of Client-Server Applications
    Host-based processing
    Server-based processing
    Client-based processing
    Cooperative processing
    “Thick client” vs“Thin server”
  • 8. 3-Tier Client/Server Architecture
  • 9. Middleware
    Standardized interfaces and protocols between clients and back-end databases
    Hides complexity of data sources from the end-user
    Compatible with a range of client and server options
    All applications operate over a uniform applications programming interface (API).
  • 10. Middleware Architecture
  • 11. Logical View of Middleware
  • 12. Basic Message Passing Primitives
  • 13. Message Passing Issues
    Reliability vs Unreliability
    Reliable facilities guarantee delivery, provide error-checking, retransmission, etc
    Alternatively, the message can be sent without success/failure; reduces complexity and overhead, passes responsibility for confirmation to application
    Blocking vs Nonblocking
    Non-blocking more efficient, but difficult to test and debug programs
    Blocking (synchronous) retains control until acknowledgment is received
  • 14. Remote Procedure Call Mechanism
  • 15. Client/Server Binding
    Nonpersistent binding
    Does not maintain state information, connections re-established as necessary
    Inappropriate for RPCs used frequently by same caller
    Persistent binding
    Connection sustained until procedure return
    Useful for applications making repeated calls to remote procedures
  • 16. Object-Oriented Mechanisms
    Clients and servers ship messages between objects.
    May rely on an underlying message or RPC structure or be developed directly on top of object-oriented capabilities in the operating system
    Success depends on standardization of the object mechanism, but competing models exist
    COM, OLE, CORBA
  • 17. Intranets
    Implementation of Internet-based technologies within an organization, rather than for global connectivity
    Immensely successful in corporate computing contexts
  • 18. Advantages of Intranets
    Rapid prototyping
    Scales effectively
    Little training required
    Can be implemented on variety of systems
    Open architecture allows interaction across platforms
    Supports a range of distributed servers
    Allows integration of legacy systems on client and server side
    Supports a range of media types
    Inexpensive to implement
  • 19. The Intranet Web
    Web Content
    The web can be used to effectively distribute content in a way that requires no new training for end-users
    Web/Database Connectivity
    Multiple tools exist to serve as middleware between web servers and data sources
    Electronic Mail
    Network News
  • 20. Corporate Intranet Example
  • 21. Web/Database Connectivity
    Advantages
    Ease of administration
    Deployment
    Development speed
    Flexible information presentation
    Disadvantages
    Limited functionality
    Stateless operation makes tracking difficult
  • 22. Intranet Webs vs Traditional Client/Server
    Client/Server Disadvantages Include:1. Long development cycles2. Difficulty in partitioning applications, and modifying based on user feedback3. Effort in distributing upgrades to clients4. Difficult in scaling servers to respond to increased load5. Continuous requirement for more powerful desktop machines
  • 23. Other Intranet Technologies
    Electronic Mail
    Closed internal mail systems (delivery verification, etc)
    Internal mailing lists
    Network news (USENET)
    Can be adopted for internal intranet uses
  • 24. Extranets
    Extends the intranet concept to provide information and services to selected outside populations, such as customers and suppliers
    Enables the sharing of information between companies
    A TCP/IP enabled form of EDI
  • 25. Advantages of Extranets
    Reduced costs
    Coordination
    Customer Satisfaction
    Expedited communication
  • 26. Methods for Converting Intranets to Extranets
    Long-distance dial-up access
    Internet access to intranet with security
    Internet access to an external server that duplicates some of a company’s intranet data
    Internet access to an external server that originates database queries to internal servers
    Virtual private network
  • 27. Service Oriented Architecture
    Client/server architecture utilized widely by enterprise systems
    Business functions consist of modular structures
  • 28. SOA Architectural Elements
    Service provider: network node that provides a service interface for a software asset that manages a specific set of tasks.
    Service requestor: network node that discovers and invokes other software services.
    Service broker: specific kind of service provider that acts as a registry and allows lookup of service provider interfaces and service locations.
  • 29. Key Characterisitics for Effective Services Use
    Coarse-grained
    Interface-based design
    Discoverable
    Single Instance
    Loosely Coupled
    Asynchronous
  • 30. SOA Example