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Distributed Data Processing. Topic 3. Outline. Data Processing Network Architecture for DDP Tiered Network Architecture Circuits. Data Processing. Centralized data processing Computer, data, control, staff and processing are centralized Distributed data processing (DDP)

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Presentation Transcript
outline
Outline
  • Data Processing
  • Network Architecture for DDP
  • Tiered Network Architecture
  • Circuits
data processing
Data Processing
  • Centralized data processing
    • Computer, data, control, staff and processing are centralized
  • Distributed data processing (DDP)
    • May include centralized center plus satellite facilities
    • Involves distributed computer, data, and processing
    • Greater flexibility in meeting individual needs
    • More redundancy and more autonomy
reasons for ddp
Reasons for DDP
  • Need for new applications
    • On large centralized systems, development can take years
    • On small distributed systems, development can be component-based and very fast
  • Need for short response time
    • Centralized systems result in contention among users and processes
    • Distributed systems provide dedicated resources
networking implications
Networking Implications
  • Connectivity requirements
    • What links between components are necessary?
  • Availability requirements
    • Percentage of time application or data is available to users
  • Performance requirements
    • Response time requirements
functions of data processing system
Functions of Data Processing System

The work done by any application program can be divided into four general functions:

  • data storage
  • data access logic
  • application logic
  • presentation logic
network architecture
Network Architecture

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Storage

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Logic

Application Logic

Data Access Logic

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network architectures
Network Architectures

From a viewpoint of distributed application system, there are three fundamental network architectures:

  • Host-based networks: the host computer performs virtually all of the work
  • Client-based networks: the client computer performs virtually all of the work
  • Client-server networks: the work is shared between the hosts and clients
host based architectures
Host-Based Architectures

The very first data communications networks were host-based, with the host computer performing all four functions. The clients enabled users to send and receive messages to and from the host computer.

This very simple architecture often works very well. Application software is developed and stored on one computer and all data are on the same computer.

client based architectures
Client-Based Architectures

In the late 1980s, there was an explosion in the use of microcomputers and microcomputer-based local area networks.

Part of this expansion was fueled by a number of low-cost, highly popular applications such as word processors, spreadsheets, and presentation graphics programs.

client based architectures12
Client-Based Architectures

With client-based architectures, the clients are microcomputers on a local area network, and the host computer is a server on the same network.

This simple architecture often works well. However, as the demands for more and more network applications grow, the network circuits can become overloaded.

client based architectures13
Client-Based Architectures

Example: Novell NetWare 3.12

client server architectures
Client-Server Architectures

More organizations today are moving to client-server architectures.

Client-Server attempts to balance the processing between the client and the server by having both do some of the processing.

costs and benefits of client server architectures
Costs and Benefits of Client-Server Architectures

Client-server architectures have some important benefits compared to host-based architectures.

  • Client-server architectures are scaleable
  • Client-server architectures can support many different types of clients and servers.
  • Because no single host computer supports all the applications, the network is generally more reliable.
client server architectures17
Client-Server Architectures

Client-server architectures also have some critical limitations, the most important of which is their complexity.

Even updating the network with a new version of the software is more complicated too.

Much of the debate between host- and client-server networks has centered on cost. Microcomputer hardware is more than 1000 times cheaper than mainframe hardware for the same amount of computing power.

middleware
Middleware

Client-server networks enable software and hardware from different vendors to be used together. Unfortunately, they have few standards. One solution is middleware, software that sits between the application software on both the client and the server.

There are dozens of standards for middleware, each of which is supported by different vendors, and each of which provides different functions.

middleware19
Middleware

Middleware does two things:

1. It provides a standard way of communicating that can translate between software from different vendors.

2. It manages the message transfer from clients to servers so that the clients need not know the specific server that contains the application’s data.

middleware20
Middleware

Examples of middleware:

  • OMG's CORBA (Common Object Request Broker Architecture)
  • Open Group’s DCE (Distributed Computing Environment)
  • DCOM (Distributed Component Object Model)
  • ODBC (Open Database Connectivity) and OLEDB
  • JDBC (Java Database Connectivity)
middleware odbc
Middleware - ODBC

Open DataBase Connectivity

  • A Microsoft’s application development standard
  • Available on Windows system
  • Application development environment example:

Cold Fusion + ODBC + Any DBMS

  • A newer version is OLEDB
middleware jdbc
Middleware - JDBC

JDBC is Java's version of the DBI module in Perl 5.

two tier three tier and n tier architectures
Two-tier, Three-tier, and N-tier Architectures

Two-tiered client-server architecture

two tier three tier and n tier architectures25
Two-tier, Three-tier, and N-tier Architectures

Three-tiered client-server architecture

n tier architectures
N-tier Architectures

N-tiered client-server architecture

5 tier example
5-Tier Example

IMW’s Forum User Database Updating

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Web

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thin clients versus fat clients
Thin Clients versus Fat Clients
  • Another way of classifying client-server architectures is by examining how much of the application logic is placed on the client.
  • A “thin client” places little or no logic on the client, and are easier to manage.
  • A “fat client” places all or almost all of the application logic on the client.
  • There is no direct relationship between thin/fat clients and 2-/3-/n-tiered architectures.
network architecture29
Network Architecture

The function of client computer

Thin

client/server

Presentation Logic

Application Logic

Client/server

Middleware

Application Logic

Data Access Logic

Client-based

Data Storage

network configuration
Network Configuration

Network configuration is the basic physical layout of the network.

There are two fundamental network configurations:

  • Point-to-point configuration (or two-point) - sometimes called dedicated circuits.
  • Multipoint configuration (or multidrop).

Most complex computer networks have many circuits, some of each type.

data flow
Data Flow

Circuits can be designed to permit data to flow in one or both directions. There are three ways to transmit:

  • Simplex - One way transmission
  • Half-duplex -Two way communications link, but only one system can talk at a time.
  • Full duplex -Transmit in both directions simultaneously.