introduction to distributed systems dr. s. indran 23 january 2004
Post on 28-Dec-2015
215 Views
Preview:
TRANSCRIPT
Organisation
Architecture and programming paradigms for distributed system developmentThe concepts of clients, servers, and middlewareDistributed paradigms
Distributed system
A distributed system in which the computer power in the system is distributed geographically around a number of computers which share the processing load of system
Network concepts
Network topologiesLayered modelsThe InternetInternet addressesDomain names and namingClients and serversPorts and sockets
Domain names and naming
Top-level domain name
Organisation
com Commercial company
edu or ac Educational
gov Governmental
mil Military
biz Show business
org Organisations not catered for above
aero Aeronautics
Architecture and programming paradigms
Message passingDistributed objects technologyEvent-based bus architecturesRemote Procedure callTuple architecture
Message passing: Requirements
Communication needs very simpleHigh performance is requiredRapid implementation is requiredThe system uses a technology that no existing protocols will communicate with
Protocols
A language which embodies the functions required by an entity in a distributed system (usually a client) which another entity provides (usually a server)
Synchronous and asynchronous message passing
Synchronous message passing involves (usually a client) in the message passing process and sending a message and a second entity (usually a server) receiving it, carrying out some processing and then sending back some responses while the first entity pauses waitingIn Asynchronous message passing, each entity does not have to wait for the next part of the dialogue they are engaged in and can carry out some other task
Distributed objects technology
A distributed object is an object which is resident on one computer and for which methods can be invoked associated with code resident on other computersThis technology hides the network from the designer and the programmer.Examples: CORBA, and RMI.
n-Tiered Architecture
A tier is a logically separated and encapsulated set of processes.There are three basic parts: The user interface tier (representation layer). The data tier (server-side component), which
is the database data processed by the Web application.
The middle tier (middle-tier component), which processes complex business processing (usually place on a separate server called the application server).
Middle-Tier Technologies
The middle-tier application development is a separated and encapsulated set of processes usually related to business applications.The applications in the middle-tier are build as components which are accessed from the server-side components (data tier).Popular technologies for building middle-tier components are: the Component Object Model (COM) with C++ and VB, and the JavaBeans with JavaThe middle tier components are usually place on a separate server called the application server.
Clients and servers
A server is a computer which carries out a service such as printing out a file or responding to a web pageA client is some computer which require service
Clients and servers
ClientsServersMiddlewareProtocolsInternal and external servicesEnterprise frameworksWhy client-server?
Types of server
A file server provides files for the clients that ask for its serviceA database servers are computers which store large collections of data which are structuredA groupware is software which organises the work of a number of staff in some enterpriseA web server is a typical type of file server that contain files which store the various components of a web siteA mail server is a computer which has the task of receiving, storing, and sending e-mailObject serversPrint serversApplication servers
Tiered architectures
Two-tier architecture (a presentation and logic layer, and a data layer)Three-tier architecture (a presentation layer, a processing (application server) layer, and a data layer
Middleware
The intermediate software between clients and severs is known as middleware General middleware is software which
is associated with services required by all clients and servers
Service middleware is associated with a specific service such as a printing a file on a remote computer
Enterprise frameworks features
Multi-language supportSupport for legacy codeSupport for high-volume transactionsMessaging supportWeb server programming
The J2EE framework components (Continued)
Java Database Connectivity (JDBC)Remote object accessEnterprise JavaBeansThe Java Messaging ServiceJava Naming and Directory Interface (JNDI)Legacy interfacing
The J2EE framework components
XML processingWeb server programmingSecurity in J2EEAccess to standard protocols
The .Net framework
Provides similar features to J2EE frameworkInvolved configuring many of microsoft products such as Excel, Word, MS Access together with supporting language such as Visual Basic, C++, and CSharp.
top related