unit 1

CLIENT SERVER TECHNOLOGY

By  M.JEHAN

Example Diagrams

• Dallas­based  American  airlines  Decision  Technologies  cut    their  computing  budget  by  90%­from  $5  million  to  under    $500,000 •   As  the  result  of  an  18  month  pjt  that  created  an  open    systems network. • Built  with  $4.5  million  worth  of  multi  vendor  UNIX  based    hardware and software. • The  company  develops  systems  for  companies  such  as    American  Airlines,  Lufthansa  German  Airlines,  Ryder    Truck Rental and Royal Caribbean Cruise Lines. • Consolidated  Insurance  Group  in  Wilmington,  Delaware,    reduced  capital  expenses  from  $1  million  to  $300,000  and    operating  expenses  from  $2.5  million  to  $500,000  in  the    first year after replacing its headquarters based IBM 3090    mainframe and support staff 30 with 7 micro based servers    supported by a staff 10.

Overview of client server computing

Contd..

• When  United  Airlines  Inc.  converted  to  a  client    /server  environment  from  mainframe  computer    environment,  the  company  saved  millions  in    computer  costs  and  improved  flight  schedules  for    its  pilots,  which  is  predicted  to  save  nearly  $1.5    million a year • How  are  these  organizations  achieving  such    savings?

Client /Server Computing

What is Client/Server Computing

• Client/Server  computing  uses  local  processing    power­ the power of the desk top platform. • Simple defn.­ Server software accepts requests    for  data  from  client  software  and  returns  the    result to the client. • The  client manipulates  the  data  and presents    the results to the user. • Tech  defn.­Most  of  the  application  processing    is done on a programmable desktop computer,    which  obtains  application  services  from    another  computer  in  a  master/slave    configuration.                                             contd..

Contd..

• The  use  of  open  systems  (hardware,    software,  operating  systems,  databases    and  networks)  enhances  client/server    computing.

Application Tasks

An application can be broken into six tasks:  • User Interface­ what are user actually sees • Presentation  Logic­  what  happens  when  the    user interacts with the form on the screen • Application logic • Data requests and results acceptance • Data  integrity­  such  as  validation,  security,    completeness • Physical  data  management­  such  as  update,    retrieval, deletion, and addition.

Query Language Architecture

• Query languages to support update, create,   retrieve and delete fns as in the above fig.

Original Client/Server Applications

• GUI require a great deal of processing power to   create the screen the user sees. • As app. Tasks were split host and the screen   generating desktop m/c as in the fig.

Distribution of processing in      client/server model

• Distribution of processing between the client and   server is accommodated by the client/server   model.

Rightsizing

• Client/server technology evolves, the battle cry   is now rightsizing- design new applications for   the platform they are best suited for, opposed to   using a default placement. • The client/server model allows the app to be split   into tasks and those tasks performed on   individual platforms. • Developers review all the tasks within an   application and determine whether each task is   best suited for processing on the server or on   the client. • Determining how the tasks are split can be the   major factor in the success or failure of   client/server app.Contd…

• Some variations on this theme are: • Downsizing: A host based app. Is downsized   when it is reengineered to run in a smaller or   LAN based environment. • Upsizing: App. that haveoutgrown their   environment are re-engineered to run in a larger   environment.

– Increasing memory and storage on the server – Swapping more powerful processor into the server. – Adding processors to the server

• Smartsizing: Technology based smart sizing   affects the entire organizational structure and   involves re-engineering and redesigning the   business process.

Growth in installed micros and             LANs

• Dollar Savings

Benefits of client/server computing

– Client/server technology allows organizations to protect current   investments by using existing equipments and protect future   investments by using scalable, expandable products. – Client/server based applications can be developed in less time   than mainframe based applications.

• Increased Productivity

– End user Productivity

• Flexible data access for end users was first provided by 4GLs

– Developers productivity

• Developers can be using client/server development tools • Most C/S tools make use of object oriented technology

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Flexibility and Scalability

– Adding new components or replacing existing ones is as straight   forward – Users can choose their own presentation interface

• Resource Utilization

– C/S architecture is designed to use LAN technology efficiently,   minimizing potential bottlenecks

• Centralized Control

– Full circle in the architecture of IS facilities

Centralized and decentralized control

• Decentralized portion of the computer system consists of   the processing done in the client and is the responsibility   of business end user. • The centralized portion of the responsibility of IS   professionals-link to the server

• Open Systems

– Client/Server computing to be effective, multiple   environments must be supported. – When applications are right sized, it is important that   there be connectivity among the components of the   platform – There must be support for multiple hardware vendors,   multiple GUI platforms, multiple OS, Multiple DBMS,   Multiple communication protocols and multiple LAN   OS – The benefits of open systems- Interoperability and   Portability

Evolution of Client/Server Computing

• Hardware Trends

– Power – Chips – Memory – 40MB hard drive is standard on an entry level   micro.

• Multiple disk drivers.

Capacities of processors

• Software Trends

– Relational Databases

• Multiple structures with multiple management   techniques

– GUIs

• MS-Windows, openLook and etc.

– Multi threaded Processing

• Thread is a process or an execution • DOS can execute only one process (thread) at a   time. • MS LAN Mgr Network OS – supports multiple   threads of execution. • One thread could controlling the printer, one the   keyboard I/O another executing app. Code.

– Continuing Evolution

• Product that generate GUIs have some intelligence   about interfaces.

• Evolution of Operating Systems

– Micro operating systems evolve, there should   be some common capabilities. These include

• Portability in the underlying kernel and app.   Programming interfaces • Use of 32 bit architecture • Support for symmetric multiprocessing hardware • Extensions for multimedia and pen based   computing • Portable OS interface for UNIX

• Networking Trends

– LAN based implementation – Token ring running LAN manager

• Business Consideration

– Dept. need more than one database. – Dealing with voice, scanned images, text and   graphic images.

Overview of Client/Server       Applications

• A client/server application has three   components: a Client, a server and a   network • Each of these components has a   hardware and a software component.

Components of the Client/Server Applications

• Servers -perform the routine. • Clients- front ends

– To many users client is the “System”

• The data management software on the   server is responsible for keeping the data   “Safe and Sound”. • Some org. have applications where clients   need to maintain concurrent connections   with more than one server-- many-to-many   relationship.

Components of Client/server computing

• The client hardware is the desktop m/c that runs client   software. • It could be a micro or a workstation • The client software formulates the data requests and   passes the requests to the network software. • This s/w send the request to the server , accepts the   result from the server and passes the result to the client   software. • The presentation component produces the interface that   the user views and interact with.

The Client

The Server

• A server is the machine that runs data   management software • Compared to a desktop micro server   hardware

– increased memory capabilities; – increased storage capabilities; – increased power; – parallel processors; – improved cycle times; – and improved reliability

• When evaluating server hardware, the following   measures should be kept in mind: • Reliability- How often does it fail? What is the   mean time between failures? • Availability- How quickly does the system come   back into service after a failure? To assure high   availability, some systems have self healing   routines, continuous processors, fault –tolerant   hardware , alarms to high light problems before   become serious. • Flexibility and Scalability. How easily can the   server be expanded as processing needs grow? • A server has operating system software, data   management software and a portion of the   network software

The Network

• The network hardware is the cabling, communicating   cards and the devices that link the server and the clients. • Connections must allow servers to access other servers   and for users (clients) to access data on any network   node • The connection devices, such as routers and wire hubs. • The communication and data flow over the network is   managed and maintained by the network software. • The network OS manages the network related input   /output processes of the server.

Classes of Client/Server       Applications

• 3 levels:-

– Host based processing – Client-Based Processing – Cooperative Processing

• Host-Based Processing

– Most client/server applications has a presentation   layer running on the desktop machine with all app.   Processing running on the server/host. – Presentation layer provides the user with an easy to   use interface. – The processing power of the desktop m/c is used to   produce this interface, which requires a great deal of   m/c resources – Host based processing applications require less   functionality on the client. – Host based processing does not permit organizations   to re-think the business process

Classes of Client/Server applications

• Client-based Processing

– Client/server applications puts all the app.   Logic on the client m/c with the exception of   data validation routines, which are coded into   the DBMS on the server. – Users can access data on any node. – Many of the host fns –security and reliability   must be built into these new client server app.

• Cooperative Processing

– app. Uses a fully cooperative peer-to-peer processing   approach. – All components of the system are equal and can   request to provide services to each other. – The processing is performed where ever computing   resources (devices, CPU, and memory are available – A single system can act as a client for other servers   and a server for other clients. – Data manipulation may be performed on both the   client and the server, whichever is more appropriate.

Categories of client/server       Applications

• Client/Serverapp.Canalsobe   categorized by their support function. • ThearchitectureofClient/Server   computing promotes group interaction,   whether it is messages, mail, shared data,   or shared app. • users of an application can be anywhere   on the network.

• Office Systems

– Client/Server computing provides a   framework for electronic communication as in   the Fig. – Users on LAN C can Communicate with users   on LAN A or LAN B

The foundation for electronic communication

• Front-Ends to Existing Systems

– Another category of client/server app. Consists   of screen emulation systems (screen-scrapers),   which convert existing character based screens   to GUI screens. – No changes are made to the existing app. on   the server – Benefits of these systems are ease of use and   increased worker productivity. – Existing products facilitate building front-ends   to existing systems. – They capture the 3270/5250 data stream and   map it into a client based display panel.

• Database access

– To provide a GUI for accessing corporate data – Query oriented app. Provide a single window   to the data of the organization.

Query oriented Applications

• Transaction-Processing Applications

– Also known as mission-critical applications, include   order entry, inventory, and point-of-sale systems. – System must run continuously.

• Investigative applications

– Transaction processing systems work with real time   data. – Investigative app. Are designed to support decision   makers. – Investigative app. Are often called Decision Support   Systems (DSS) or Executive Information Systems   (EIS). – Ref. next slide pic.

Snapshots of Data for investigative applications

Understanding Client/Server         Computing

• Dispelling the Myths

Many myths promoted by Marketing literature, others are promoted by the press, more by omission than inclusion.

– Client/Server Computing is Easily Implemented – Current Desktop Machines are sufficient – Minimal Training is Required – All Data are Relational – Development time is Shorter

Obstacles-Upfront and Hidden

– Client server computing is not the easy task that   marketing literature would have us believe. – They are some very real, and painful, hurdles on the   road to success

• Costs

– Cost saving prompt organizations to consider   client/server computing – Conservative figures for the cost per MIPS (millions of   instructions per second) are: – IBM Mainframe-About $100,000 – Midrange-About $50,000(includes some bandwidth   processors) – Desktop-About $300

• Mixed Platforms

– In the past, most org. operated homogeneous   centralized mainframe and midrange   processors and terminal n/w – Managed separately-independent systems   and protocol – Today, org have at least two micro OS,   multiple n/w OS and variety of n/w topologies.

• Maintenance

– It is costly and time consuming

• Reliability

– H/w must be stable and include backup units   and monitoring s/w for the system itself.

• Restructuring Corporate Architecture

– Client/server technology also restructures the   workflow processing. – Electronic data interchange (EDI) is an   example of a modification in workflow   processing.

Open Systems and Standards

• To Business end users, open systems mean easy access   to information • The IEEE – open systems offers the following definition

“A  comprehensive  and  consistent  set  of  international    information  technology  standards  and  functional  standards    profiles that specify interfaces, services, and supporting formats to    accomplish  interoperability  and  portability  of  applications,  data    and people.” Standards Areas        Four areas of client/server computing • Platforms­Developed by hardware and software vendors­ such as    Intel chips, UNIX, and DOS with Windows. • Networks­N/W protocols­ such as OSI and TCP/IP • Middleware­ Between App. and the OS, includes GUIs, database,    E­Mail systems • Applications­  Org.  decide  on  std  app.  to  facilitate  work  group    interaction

Existing Standards • Currently, there are recognized stds for server OS   environment and for network protocols

– UNIX – POSIX-Portable Operating Interface from IEEE is a   UNIX based specification. – TCP/IP-to connect LAN Based micros to corporate data   on a UNIX host. – OSI- to provide a common basis for communication – RDA and DRDA - Remote Data Access (RDA)   Architecture and Distributed Relational Database   Architecture – Distributed data management

Open Systems

Components of an open systems environment

• Factors for Success

– Identify the business motivation for the change to   client/server computing. – Whether it is reduced costs, increased productivity,   or a competitive advantage, implementation of the   new technology. – Internetworking –LAN,WAN – Interoperability-ability to interact

• Considering client m/c, client s/w, n/w, n/w s/w, server   and server s/w.

– Compatible Environments- whenever possible,   avoid mixing architectures – Perceived Benefits- ease-of use, cost saving,   response time, functionality, accessible data.

Host

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The term "host" is used in several contexts, in each of which it has a slightly different meaning: 1) In Internet protocol specifications, the term "host" means any computer that has full two-way access to other computers on the Internet. A host has a specific "local or host number" that, together with the network number, forms its unique IP address. If you use Point-to-Point Protocol to get access to your access provider, you have a unique IP address for the duration of any connection you make to the Internet and your computer is a host for that period. In this context, a "host" is a node in a network. 2) For companies or individuals with a Web site, a host is a computer with a Web server that serves the pages for one or more Web sites. A host can also be the company that provides that service, which is known as hosting. 3) In IBM and perhaps other mainframe computer environments, a host is a mainframe computer (which is now usually referred to as a "large server"). In this context, the mainframe has intelligent or "dumb" workstations attached to it that use it as a host provider of services. (This does not mean that the host only has "servers" and the workstations only have "clients." The server/client relationship is a programming model independent of this contextual usage of "host.") 4) In other contexts, the term generally means a device or program that provides services to some smaller or less capable device or program.

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