client/server computing ajay kumar shrivastava. what is client/server clients and servers are...
Post on 22-Dec-2015
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What is Client/Server
• Clients and servers are separate logical entities that work together over a network to accomplish a task
Characteristics
• Service• Shared resources• Asymmetric protocols• Transparency of location• Mix-and-match• Message based exchanges• Encapsulation of services• Scalability• Integrity
Comparison b/w 2-Tier & 3-Tier2-Tier 3-Tier
System administration Complex (more logic on the client to manage) Less complex
Security Low (data-level security) High
Encapsulation of data Low (data tables are exposed) High (the client invokes services or methods)
Performance Poor Good
ScalePoor (limited management of client communications links)
Excellent (concentrates incoming sessions; can distribute loads across multiple servers)
Application reuse Poor (monolithic application on client) Excellent (can reuse services and objects)
Ease of development High Getting better
Server-to-server infrastructure No Yes (via server-side middleware)
Legacy application integration NoYes (via gateways encapsulated by services or objects)
Internet support Poor Excellent
Heterogeneous database support No Yes
Rich communication choicesNo (only synchronous, connection-oriented RPC-like calls) Yes
Hardware architecture flexibility Limited (you have a client and a server) Excellent
Availability Poor Excellent
Advantages of Component based Middle Tier
• You can develop big applications in small steps• Applications can reuse components• Clients can access data and functions easily
and safely• Custom applications can incorporate off-the-
shelf components• Component environments don't get older—
they only get better
When Should You Use 3-Tier?
• More than 50 applications• Written in different languages or by different
organizations • Heterogeneous data sources• Life longer than three years• Many modifications or additions• A high-volume workload• Significant inter-application communication• Expectation of growing the application
Web C/S Versus Traditional C/S
Application CharacteristicsIntergalactic Era Client/Server Ethernet Era Client/Server
Number of clients per application Millions Less than 100
Number of servers per application
100,000+ "Server-mania" with many heterogeneous servers performing different roles 1 or 2
Geography Global Campus-based
Server-to-server interactions Yes No
Middleware ORBs on top of Internet SQL and stored procedures
Client/server architecture 3-tier (or N-tier) 2-tier
Transactional updates Pervasive Very infrequent
Multimedia content High Low
Mobile agents Yes No
Client front-endsOOUIs, JavaBeans, Webtops, browsers, and shippable places Fat GUI clients
Timeframe 1998 and beyond 1985 till present
What Do We Need
• Rich transaction processing• Roaming agents• Rich data management• Intelligent self-managing entities• Intelligent middleware
Inside the Building Blocks
• The client building block • The server building block • The middleware building block
Middleware
• A hodgepodge of s/w technologies• A buzzword• A key to developing client/server applications
• Middleware is a vague term that covers all the distributed software needed to support interactions b/w clients and servers.
Middleware continue
• Starts with API• Covers transmission from request to result
• Not includes-S/w that provide the actual service- Database- User interface.
Classes of Pipes• General pipes • Service-specific pipes
-Database-specific-OLTP-specific-Groupware-specific -Object-specific-Internet-specific -System management
The Transport Stacks Middleware
• The stack sandwich• The logical network driver• The transport-independent APIs
Boundless Bandwidth: How Much Is Enough?
Content Bandwidth Requirements Remarks
Audio
п CD quality 706 Kbit/s44,100 samples/sec, 16-bit per sample
п Digital phone quality 64 Kbit/s 8,000 samples/sec, 8-bit samplesMinimum-quality, full-motion video 566 Kbit/s
1024 × 768 pixels, 30 frames/sec 3 colors; 8 bits each
TV-quality, full-motion video
п Uncompressed 96 Mbit/s
п MPEG-2 compression 6 Mbit/s
Data requirements 2 Mbit/s For LAN-speed responsiveness
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