understanding networked applications: a first course midterm one review by david g. messerschmitt
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Understanding Networked Applications:A First Course
Midterm one review
by
David G. Messerschmitt
Understanding Networked Applications A First Course2
Copyright notice
©Copyright David G. Messerschmitt, 2000. This material may be used, copied, and distributed freely for educational purposes as long as this copyright notice remains attached. It cannot be used for any commercial purpose without the written permission of the author.
Understanding Networked Applications A First Course3
Major topics
• Past and future of computing and networking– mobility, ubiquity, embedded
• Applications– social– information management– business– e-commerce
Understanding Networked Applications A First Course4
Major topics (con’t)
• Information technology– information– processing, storage, communication– internet
• Client-server computing– two and three tier– Web
Understanding Networked Applications A First Course5
Major topics (con’t)
• Architecture– decomposition and modularity– granularity and hierarchy– interfaces and data types
• Layering– network, operating system, middleware,
application
Understanding Networked Applications A First Course6
Major ideas
• Information technology– information (content) represented as data– processing– storage– communication
Understanding Networked Applications A First Course7
Role of the Computer
Number cruncher
Informationmanagement
Communication
Time….
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Past and future
• Past– centralized, timeshare, decentralized,
networked
• Future– embedded, ubiquitous, mobile
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Application
• Application = something that puts technology to use to the benefit of someone
• Technology = something that puts scientific principles to use
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Types of applications
• Individual = entertainment or productivity
• Social = groups of users
• Information management = access to or manipulation of information
• Educational = contribute to learning or training
• Organizational = aid mission or operations
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Task group
Categories of user groups
Individual
Work group
Interest group
Citizenry
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Styles of social applications
Direct
Publication
Immediate Deferred
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A hierarchy
• Data
• Information
• Knowledge
• Wisdom
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Participants
User
Author or publisher
Indexer or organizer
Recommender
Librarian or teacher or interpreter
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Push vs. pull
User
Publisher
Pull
Control over what is providedTime when it is provided
PushIntermediate cases:
NotificationSubscription
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Some modalities of information accessPull
Push
Agent
Intermediary
Aggregate,filter,consolidate
Delegate
Search,navigate,browse
Subscribe
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Taxonomy of organizational applications
Department
Enterprise
Economy
E-commerce:Inter-enterpriseConsumerInter-consumer
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Hierarchical,functional organization
Suppliers
Customer
ActivityFlow of material,goods, and information
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Book distributioncenters
books4u.comCustomers
Financial institution
Consumer Enterprise Inter-enterprise
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Two flavors
• Supply chain management: extension of ongoing business processes to suppliers and customers– primarily business to business
• Marketplace: dynamic, opportunistic transactions conducted over the network– primarily business to consumer
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Steps in an e-commerce sale
• Matching buyers and sellers
• Negotiating terms and conditions– price, delivery, warrantee, etc.
• Consummation– order, fulfillment, payment
• Post-sale customer service
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Key concept
• The key commodity manipulated by information technology is information
• To be manipulated in a computing/networking environment, information must be represented by data
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Representation needs to be standardized
Information
Data
Information
Data
Communicate data toanother user or organization
If the representationis not standardized, theinformation is garbled!
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Decomposition
Decomposition
Functionality
Interaction
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A system is decomposed into interacting subsystems
Each subsystem may have a similar internal decomposition
Architecture
Understanding Networked Applications A First Course26
Layering
Existing layers
Elaboration or specialization
Layering builds capability incrementally by adding to what exists
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Communications Storage
Network equipment Storage peripherals
Network software File system
Distributed objectmanagement
Databasemanagement
Application
Middleware
Operatingsystem
Equipment
Simplified infrastructure layering
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Applications
Integrative services
Generic services
Common representations
Processing Storage Connectivity
Application components
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The basic idea
Diversity of applications
Diversity of processing, storage, andconnectivity technologies
Common services andrepresentationsand structures forinformation
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Hosts
Switches
Backbonelinks
Access links
Network architecture
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Presentation
Applicationlogic
Shareddata
Local-area network
Note: many clients perapplication server, severalapplication servers per data server
Three-tier client/server
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Modularity
• A system is modular when it is divided into subsystems (called modules) with “good” properties– Modules embody distinct functional groupings– Hierarchy supports views at different
granularity and scale– Separation of concerns among modules– Reusability
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Software:
Allows a system to be understood at different granularity
Hierarchy
Organization:Allows a managerto focus on high-levelobjectives, delegatinglow-level detail
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Interfaces
• Focus of module interaction and interoperability
• Two purposes:– informs other modules how to interact– informs implementer as to what has been
promised to other modules
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Module interaction through interfaces
Client Server
action, parameters
returns
Both subsystems areaffected by the interaction
Data customizing an actionand disclosing its results
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Layer above is a client of thelayer below
Layer below as as a serverto the layer above
….by utilizing the services of the layer below and adding capability
Each layer provides services to the layer above….
Interaction of layers
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Web browser
File system
Operatingsystem
File
Network
Message
Collection of packetsFragmentation Assembly
Message
HTML
Screen
Application
Web server
Example