Client Server Technologies Middleware Technologies

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Client Server TechnologiesMiddleware Technologies

• Ganesh Panchanathan
• Alex Verstak

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Overview

• Ganesh
• Client/Server technologies
• Middleware
• Alex
• DirectExchange
• Sequoia 2000
• 3-Tier Architecture on the Grid

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Computing models

• Terminal host model
• File sharing model
• Client/Server model
• Peer to Peer model

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Client/Server model

• Client/server model is a concept for describing
• communications between computing processes
• that are classified as service consumers
  (clients)
• and service providers (servers).
• 2 Tier
• 3 Tier
• N Tier

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Two Tier C/S Architecture

• Layers
• Clients
• Servers
• Functionalities
• User Interface Client
• Business Logic Client (Server??)
• Database management Server

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3 Tier C/S Architecture

• Presentation Tier
• Business Tier
• Database Tier

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2 Tier vs. 3 Tier

• Modularity
• Change management
• Reuse
• Performance
• Scalability
• Multiple data sources
• ????

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Example N-Tier Architecture
J2EE Application Model
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Middleware

• Middleware is a class of software
• technologies designed to help manage
• the complexity and heterogeneity
• inherent in distributed systems.

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Middleware
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Middleware

• Enable multiple processes interact across a
  network
• Between Apps and OS/Network services
• More functional API for
• Heterogeneity
• Location transparency
• Reliability
• Scalability

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Types of middleware

• Middleware can take the following forms
• Remote procedure call
• Object request broker
• Transaction Processing monitor
• Message oriented middleware

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Transaction

• A Transaction means a sequence of
• information exchange and related work
• (such as database updating) which is
• treated as an unit for the purposes of
• satisfying a request and ensuring
• database integrity.

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Examples of transactions

• Purchase online using credit card
• Withdraw money from ATM
• Electronic funds transfer
• Book an airline ticket
• Ordering in Inventory management
• Billing for phone calls

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Transactional Integrity - ACID

• Atomicity
• Trans. must be done or undone completely
• Consistency
• One consistent state to another
• Isolation
• Each trans. must be independent of others
• Durability
• Completed transactions are permanent

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Transaction Processing Monitor

• Monitors a transaction as it passes
• through the different stages to
• Guarantee integrity of transaction
• Runtime resource management

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TP Monitors

• Clients connect to the TP monitor
• TP Monitor
• Accepts transactions
• Queues them
• Takes responsibility till they are finished
• Two types
• TP Heavy
• TP Lite

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Features

• Maps requests to controlled set of processing
  routines for performance
• Ability to update multiple DBMSs in a single
  transaction
• Connectivity to flat files, non relational DB and
  legacy data
• Prioritize transactions

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Vendor Implementations

• Tuxedo by BEA
• JTS by Java
• MTS by Microsoft
• CICS by IBM

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Message Oriented Middleware

• Messaging is an asynchronous method of
• passing information between processes
• across network
• across platform and OS

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Message Oriented middleware

• Message Self contained object
• Message header address, id, priority
• Body of the message
• Message is intelligent when compared to a
  transaction in TP systems.
• In TP systems
• Transactions are just packets
• Intelligence to handle them is in monitor

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Message Oriented Middleware
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Features of MOM

• Primarily asynchronous communication
• Point to multi-point
• Ordered delivery
• Receipt notification
• Handling duplicates
• Message queues FIFO or priority basis
• Messages persistent or non-persistent

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Point to point messaging

• Client may be only sender, only receiver or both
• Single receiver
• Use of a message queue

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Publish Subscribe messaging

• Free sender from knowing the receivers
• Messages are categorized on topics
• List of senders/receivers is dynamic

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Vendor Offerings

• MQSeries by IBM
• JMS by Java
• MSMQ by Microsoft
• DECMessageQ by BEA

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References

• Client/Server
• http//edocs.bea.com/tuxedo/tux80/atmi/intbas3.htm
  
• http//www.sei.cmu.edu/str/descriptions/clientserv
  er.html
• http//www.sei.cmu.edu/str/descriptions/threetier.
  html
• Middleware
• http//www.sei.cmu.edu/str/descriptions/middleware
  .htm
• http//www.eecs.wsu.edu/bakken/middleware.pdf
• http//www.execpc.com/gopalan/mts/msmq.html
• http//proj-cmw.web.cern.ch/proj-cmw/workshop/mom.
  pdf