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Note for Cloud Computing - CC By Sonam Choudhary

  • Cloud Computing - CC
  • Note
  • Maharaja Ganga Singh University - MGSU
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1 Distinct characteristics of C/S Client-server is a computing architecture which #01 Client/Server Computing  CLIENT/SERVER COMPUTING AND WEB TECHNOLOGIES  Server provides the service  Client is considered as the customer requesting the service separates a client from a server Distinct characteristics of C/S  Clients must request or initiate the service  The location of the server in the network is transparent to clients  Transaction between C/S is message-passing based     It is almost always implemented over a computer network  The most basic type of client-server architecture employs only two types of nodes: clients and servers. horizontally (more clients can added)  Vertically (more servers can be added)  It allows devices to share files and resources.  File servers  Database servers    Example: Query in DBMS server  Typically one single request/reply  Transaction server includes DBMS and transaction monitoring  Server has remote procedures run online by the client Web servers Internet Server Application Two-Tier vs. Three-Tier  Same basic idea as fat-client versus fat-server  Depends on how the application is divided between the server and the client  Two-tier servers Fat servers    Examples: file servers and database server  In this case the process (application logic) is buried within the client or server (or both) Three-tier servers  Examples: Web and distributed objects  In this case the process is run on the middle-tier – separated from the user and data interface  They can integrate the data from multiple sources  More robust and more scalable Application Server Super-fat servers and thin clients Uses HTTP protocol Client Java  Client Client Client HTML 5 The server more complicated  The clients are less complex  More of the code runs on the server  The network interaction is minimized Client Transaction servers The server is centrally maintained where as clients are independent of each other The bulk of the application is running on the client The client knows how the data is organized and where it is  Different clients access the same applications different ways 4 Server Passing file results  Where to push the application to Fat clients File sharing and file processing     This type of architecture is sometimes referred to as two-tier. Systems with C/S Architecture C/S architecture is scalable    Client/Server Models  3 The server service can be shared among a number of clients  2 6

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Tier Architecture Presentation Logic 7 Business Logic Client (dumb) - Server Model Data Source 2 Tier - Fat Client Server Client Client Server Presentation Logic 2 Tier - Thin Client (or Fat Server) Client Network Server Application Logic 3 Tier Client Application Server DBMS Database Server True Client-Server Model 9 Distributed Client-Server Model Server Client Application Logic Application Logic Network 10 Server Client Application Logic Presentation Logic 8 Network DBMS DBMS Presentation Logic Client/Server Computing  Logical extension of modular programming  11 Client/Server Computing  appropriate hardware and software platforms for with assumption that separation of a huge program into their functions. modules can create  Clients and Servers are running separately on  For example, database management system servers  the possibility for further modification  easier development running on platforms specially designed and  better maintainability. configured to perform queries, or file servers running on platforms with special elements for managing files. All large modules need not all be executed within the same memory space.  Components in Client-Server Computing  Client  the calling module becomes the client( requesting service)  Server  the called module becomes the server (providing service).  Middleware In client-server computing major focus is on SOFTWARE 12

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Middleware Software 13 It is the (/) between client and server which glues them together  Allowing the client request for a service and the server providing it  Middleware can also be between server/server  Two broad classes  General calling procedure 14 called procedure  3. results Six types of middleware 2. called procedure (client) Network Remote Procedure Call 1. arguments Database specific: SQL request message Internet specific: HTTP  arguments  reply message Groupware specific: SMTP results Used to accomplish a specific task  server stub network transport reply message Application specific  results LAN servers, TCP/IP, Communication stacks, Queuing services, etc. request message  arguments  client stub network transport calling procedure (client) 15 Local Procedure Call Six types of middleware 16 Asynchronous Remote Procedure Calls (RPC) 4. Message-Oriented Middleware (MOM) • client makes calls to procedures running on remote computers but does not wait for a response • If connection is lost, client must re-establish the connection and send request again. • High scalability but low recovery, largely replaced by type 2 • asynchronous – sends messages that are collected and stored until they are acted upon, while the client continues with other processing. 5. Object Request Broker (ORB) Synchronous RPC • distributed program may call services on different computers • makes it possible to achieve this without detailed coding (e.g. RMI in Java) • object-oriented management of communications between clients and servers. • ORB tracks the location of each object and routes requests to each object. Publish/Subscribe (often called push technology) • server monitors activity and sends information to client when available. • It is asynchronous, the clients (subscribers) perform other activities between notifications from the server. • Useful for monitoring situations where actions need to be taken when particular events occur. Computing Model File Transfer Model Distributed Computing Model Client/Server Model • middleware between applications and database servers. 17 Computing Model Terminal Host Model 6. SQL-oriented Data Access Peer to Peer Model • Has the capability to translate generic SQL into the SQL specific to the database References  Farid Farahmand, "An Introduction to Client/Server Architecture"  Rajkumar Buyya, "Client/Server Computing (the wave of the future)"  Albert Yau, "Client Server Computing", http://www.doc.ic.ac.uk/~nd/surprise_95/journal/vol1/wcy/article1.html 18

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