1.Mod1 Cs Architecture

7/28/2019 1.Mod1 Cs Architecture

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CLIENT / SERVER ARCHITECTURE


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AU Distance Education DMC1754 - Middleware Technologies - Unit I

CLIENT / SERVER MODEL

Model or architecture describes therelationship between two computer programs

Client & Server

Client is the requester that makes a servicerequestServer fulfills the request or services therequestMultiple client programs share the services of a common server program


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Servers typically contain data files &applications accessed by multiple clientsClient & Server share the processing loadClient / Server can be on same computersystem or on different computer systemsClient/Server model - a convenient way tointerconnect programs distributed acrossdifferent locations


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Server can range from PCs to mainframesStandard Server hardware

Support for large amount of RAMFast input and outputFast network cards

Ability to support multiple processorsSupport for fault tolerance


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Function of Client / Server

ClientInitiates requestsWaits for and receives repliesCan connect to several servers at the same time

Typically interacts directly with end-users using aGraphical User Interface (GUI)Server

Waits for requests from clientsUpon receipt of requests, processes them and then servesrepliesUsually accepts connections from a large number of clientsTypically does not interact directly with end-users


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Transaction Processing Example

Transaction Get Balance in a Bank AccountSteps

User initiates request giving bank account number (Client

program )Main Server at Bank (Server program) services therequest by contacting the Database server

o Sends a request (Client Program) to the Database Server alongwith the bank account number

o Database Server (Server Program) retrieves the bank balanceusing the bank account number and returns the value

Main server at Bank (Server Program) returns thebalance amount to the user (Client Program)


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CLIENT / SERVER Transaction Processing

CLIENT

MAIN SERVER

DATABASE SERVER

1

2

3

4


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CLIENT/SERVER ARCHITECTURE IN THE WEB

World Wide Web (WWW) or Web revolves aroundthe client/server architectureClient computer system uses Browsers ( like InternetExplorer, Netscape Navigator, Mozilla etc. ) tointeract with Internet servers using ProtocolsProtocols help in the accurate transfer of data -requests from browser & responses from serverCommonly used protocols :

HTTP (Hyper Text Transfer Protocol)FTP (File Transfer Protocol)SMTP (Simple Mail Transfer Protocol)


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Client / Server ModelStatic HTML Pages


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Client / Server ModelDynamic HTML Pages


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Client / Server ModelServer side Scripting


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FILE SERVER


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FILE SERVER

Objectives of File ServerTo promote sharing of files (computerprograms and/or data)

To encourage indirect or implicit (viaprograms) use of remote computers

To shield a user from variations in file storagesystems among hosts

To transfer data reliably and efficiently


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Database Server

A computer in a LAN dedicated to databasestorage and retrievalThe database server holds the DatabaseManagement System (DBMS) and thedatabasesUpon requests from the client machines, it

searches the database for selected records andpasses them back over the network


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Database Server - Example

Software Project Team sharing a database


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APPLICATION SERVER

Application server runs the programs andprocesses the dataApplication servers are typically used forcomplex transaction-based applicationsApplication server performs the businesslogic functions and some data access

An application server provides middle tierprocessing between the user's machine andthe database management system (DBMS)


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Two-Tier Architecture - Internet


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Three -Tier Architecture - Internet


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Multi -Tier Architecture


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Advantages of Client/Server

Distribution or sharing of processing loadamong several independent computersCentralized data storage on server, hence

easy to implement security of data accessClients with the appropriate permissions maybe permitted to access and change dataCentralized data. Hence easy to administerIs capable of functioning with multipledifferent clients each with differentcapabilities


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Disadvantages of Client/Server

Traffic congestion on the network (number of simultaneous client requests to a server) cancause a server to become overloaded and

unable to service clients requestsUnder client-server, should a critical serverfail, clients requests cannot be fulfilled.

Hence, lack of robustness is a cause forconcern


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In computing, a file server is a computer attached to a network that has the primary purpose of providing a location for shared disk access , i.e. shared storage of computer files (such asdocuments, sound files, photographs, movies, images, databases, etc.) that can be accessed by theworkstations that are attached to the same computer network. The term server highlights the roleof the machine in the client server scheme, where the clients are the workstations using thestorage. A file server is not intended to perform computational tasks, and does not run programson behalf of its clients. It is designed primarily to enable the storage and retrieval of data whilethe computation is carried out by the workstations.ile servers are commonly found in schools and offices, where users use a LAN to connect their client computers.Types of file serversA file server may be dedicated or non-dedicated. A dedicated server is designed specifically for use as a file server, with workstations attached for reading and writing files and databases.File servers may also be categorized by the method of access: Internet file servers are frequentlyaccessed by File Transfer Protocol (FTP) or by HTTP (but are different from web servers , thatoften provide dynamic web content in addition to static files). Servers on a LAN are usuallyaccessed by SMB /CIFS protocol ( Windows and Unix-like ) or NFS protocol (Unix-like systems).Database servers , that provide access to a shared database via a database device driver,are not regarded as file servers.

http://en.wikipedia.org/wiki/Shared_disk_accesshttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Web_serverhttp://en.wikipedia.org/wiki/Server_Message_Blockhttp://en.wikipedia.org/wiki/CIFShttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Network_File_System_(protocol)http://en.wikipedia.org/wiki/Database_serverhttp://en.wikipedia.org/wiki/Database_serverhttp://en.wikipedia.org/wiki/Network_File_System_(protocol)http://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Unix-likehttp://en.wikipedia.org/wiki/Microsoft_Windowshttp://en.wikipedia.org/wiki/CIFShttp://en.wikipedia.org/wiki/Server_Message_Blockhttp://en.wikipedia.org/wiki/Web_serverhttp://en.wikipedia.org/wiki/File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Local_area_networkhttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Client%E2%80%93serverhttp://en.wikipedia.org/wiki/Shared_disk_access

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