distributed systems lecture 01

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DISTRIBUTED SYSTEMS: LECTURE 1 INTRODUCTION TO DISTRIBUTED SYSTEMS SPRING 2005: 1iMRAN iHSAN

Distributed Systems

Lecture 1

Introduction

iMRAN iHSANLecturer

Faculty of Engineering Science & Technology

Hamdard Institute of Information Technology

Hamdard University, Karachi

Islamabad Campus, Islamabad


Course Information

Course Title : Distributed Systems

Instructor : iMRAN iHSAN

Course Code : CS 408

Credit Hours : Three (3) (Three hours theory)

Class : BSSD - VIII

Semester : Spring 2005

Pre-requisite : Introductory Parallel and Distributed

Programming, Programming Methodology (OOProgramming), Data-Structures, ComputerArchitecture. Familiarity with the UNIXoperating system and knowledge of Java,C++, or C required.

Class Times : Tuesday : 12:00 13:30

Wednesday : 10:00 11:30


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Text Book

Distributed Systems:

Principles and Paradigms

By : Andrew S. Tanenbaum

Maarten van Steen


Reference Book

Distributed Systems:Concepts and Design (3rd Ed)

By : George CoulourisJean DollimoreTim Kindberg


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Introduction

This course will introduce students to fundamentals parallel anddistributed programming. The course will cover the current paralleland distributed architecture, basic issues in parallel/distributedapplication development, parallel/distributed algorithms, data-

structures and programming methodologies, and currenttechnologies. The course will be a hands-on course withprogramming assignments and a final project


Objective

This course will focus on the current practices in parallel anddistributed computing technologies including systems, architectures,programming models, languages and software tools. The first partof the course will consist of lectures covering key issues inparallel/distributed computing. The second part of the course willcover current research in Distributed computing, and will consist ofstudent presentations. The course will require students to researchand present a topic and complete a final project.


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Assignment / Programs

Attendance is mandatory. Every class is important. Assignments aredue at the beginning of the every week class. Under normalcircumstances, late work will not be accepted. Students are requiredto take all quizzes. No make-up quiz will be given under normal

circumstances. Programs are submitted at the beginning of the classperiod on the due date. Programs in assignments are normally dueon every week first class. No programs will be accepted after thenext first lab every week.

Students are expected to do their own programs. Students copyinganother person's work or allowing their work to be copied canexpect one of the following actions to be taken by the instructor.

Both students will receive negative points equal to the assignment

Both students will have their final grade lowered by one letter grade


Attendance

80% attendance is mandatory.

Late comer will be marked as absent.


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Evaluation Criteria

Assignments/projects 05 + 10

Quizzes 05

Mid-Term 40 (Best Two will be selected)

Final 40


Lecture Plan

MIDTERM ILecture 10

Java RMIRMI TutorialLecture 9Week 5

Parameter Passing, DCE Remote Objects, Java RMILecture 8

Distributed Objects, Binding a Client to an Object, Staticversus Dynamic Remote Method Invocations

Remote ObjectInvocation

Lecture 7Week 4

NetbulaRPC, RPCGenRPC TutorialLecture 6

Basic RPC Operation, Parameter Passing, Extended RPCModels, DCE RPC

RemoteProcedure

Call

Lecture 5Week 3

Lower-Level Protocols, Transport Protocols, Higher-LevelProtocols

LayeredProtocols

Lecture 4

Clients and Servers, Application Layering, Client-ServerArchitectures

Client-ServerModel

Lecture 3Week 2

Multiprocessors, Distributed Operating Systems, NetworkOperating Systems, Middleware

Lecture 2

Connecting Users and Resources, Transparency, Openness,Scalability

IntroductionLecture 1Week 1


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Lecture Plan

MIDTERM IILecture 18

Migration in Heterogeneous Systems, D'AgentsLecture 17Week 9

Approaches to Code Migration, Migration and LocalResources

Code MigrationLecture 16

General Design Issues, Object ServersServersLecture 15Week 8

User Interfaces, Client-Side Software for DistributionTransparency

ClientsLecture 14

Introduction to Threads, Threads in Distributed SystemsThreadsLecture 13Week 7

Message-Oriented Persistent Communication, IBMMQSeries

Lecture 12

Persistence and Synchronicity in Communication,Message-Oriented Transient Communication

Message- OrientedCommunication

Lecture 11Week 6


Lecture Plan

MIDTERM IIILecture 26

Reference Listing, Identifying Unreachable EntitiesLecture 25Week 13

The Problem of Unreferenced Objects, Reference Counting,RemovingUnreferencedEntities

Lecture 24

Home-Based Approaches, Hierarchical ApproachesLecture 23Week 12

Naming versus Locating Entities, Simple SolutionsLocating MobileEntities

Lecture 22

The Implementation of a Name Space, The Domain NameSystem, X.500 206

Lecture 21Week 11

Names, Identifiers, and Addresses, Name ResolutionNaming EntitiesLecture 20

Software Agents in Distributed Systems, Agent TechnologySoftware AgentsLecture 19Week 10


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Lecture Plan

PRESENTATIONSLecture 32

The Transaction Model, Classification of Transactions,Concurrency Control

DistributedTransactions

Lecture 31Week 16

Centralized Algorithm, A Distributed Algorithm, AToken Ring Algorithm, Comparison of the ThreeAlgorithms

Mutual ExclusionLecture 30

The Bully Algorithm, A Ring AlgorithmElection AlgorithmsLecture 29Week 15

Lamport timestamps, Vector timestampsLogical ClocksLecture 28

Physical Clocks, Clock Synchronization Algorithms,Use of Synchronized Clocks

ClockSynchronization

Lecture 27Week 14


Revolution in Computer Systems

Until about 1985, large and expensive computers

Very few computers in an organization

Lack of networks

Two main advances in technology

Powerful low cost microprocessors

High-speed computer networks

Now its possible to put together computing systems

Large numbers of computers

Connected through high-speed networks

Called distributed systems


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Definition of a Distributed System

A collection of independent computers that appears to its users as asingle coherent system.

Independent computers

Autonomous systems Hardware issue

Single coherent system

Distribution of system hidden from user

Apparently one system for user.


Important Characteristics of DS

Hidden distributed aspect of the system

User Interaction: Consistent and Uniform

Easy to expand or scale

Continuously Available

To support heterogeneous computers and networks while offering

a single system view, distributed systems are often organized by

means of a layer of software that is logically placed between a

higher level layer and lower level physical layer


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Definition of a Distributed System

A distributed system organized as middleware.

Note that the middleware layer extends over multiple machines.


Distributed System Example 1

A Network of workstations in a university or company department.

Personal workstations for each user.

A pool of processors in a room, allocated dynamically as needed.

A single file system

When a user types a command, the system looks for best place toexecute it( own or someone elses idle workstation or unassignedprocessors)

If whole system looks & acts like classical single-processortimesharing system, it qualifies as a Distributed System


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Workflow Information System

Supports automatic processing of orders.

System is used by people of several departments (differentlocations).

Orders are placed by means of Laptops, connected throughtelephone or cellular phones.

Incoming orders are automatically forwarded to planningdepartments.

New internal shipping orders to stock department and billing ordersto accounting departments.

Users are totally unaware of how orders physically flow throughsystem. (behaves like Centralized Database)



World Wide Web

It offers a simple, consistent and uniform model of distributedSystem.

Uniform Resource Locator (URL) are used to publish a document.

If Web appear to its users as a gigantic centralized documents

system, it would qualify as a Distributed system.

We have not reached this point yet.

Users are aware of the fact that documents are on different placesand handled by different servers.


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Goals of a Distributed System

The four important goals of Distributed System are:

Connectivity

Easily connect users to resources

Transparency It should hide the fact that resources are distributed across a

network.

Openness

It should be open

Scalability

It should be scalable



Connecting users and resources (connectivity)

Sharing of Resources (More Economic)

Easy access to remote resources

Sharing in a controlled way

A resource can be a printer, a computer, hard disk, files, web pagesand networks etc.

Collaboration and information exchange (Easy)

IP Phone, Video conferencing, voice chat are examples.

Connectivity of Internet leading of Virtual Organizations

Groupware; software for collaborative editing, teleconferencing

E-Commerce allows us to buy and sell all kinds of good withoutactually having to go to a store

Connectivity and sharing increases, security becomes more important


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Transparency

Hide the fact that processes and resources are physically distributedacross multiple computers.

Different forms of transparency in a distributed system Access

Location

Migration

Relocation

Replication

Concurrency

Failure

Persistence



Hide whether a (software) resource is in memory or on diskPersistence

Hide the failure and recovery of a resourceFailure

Hide that a resource may be shared by several competitive usersConcurrency

Hide that a resource is replicatedReplication

Hide that a resource may be moved to another location while in useRelocation

Hide that a resource may move to another locationMigration

Hide where a resource is locatedLocation

Hide differences in data representation and how a resource is accessedAccess

DescriptionTransparency


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Degree of Transparency

Blindly hide all distributed aspects from users is not always a good idea.

It should be considered together with other issues such as

performance.



Openness

System offers services according to standard rules.

Rules describe the syntax and semantics of those services.

Services are specified through interfaces using Interface definitionLanguage (IDL).

Interface definition specify function name, parameters, return type,exceptions etc.

Semantics of the Interface: hard part is specifying precisely what thoseservices do?

Interoperability and Portability Flexibility: easy to configure the system out of different components

possibly from different developers

Separating policy from mechanism


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Scalability

Three different dimensions (Neuman, 1994)

Size (add more users & resources easily)

Geographically scalable

Administratively Scalable (easy to manage)



If more users or resources need to be supported, we are oftenconfront with some limitations

Scalability limitations examples.

Doing routing based on complete informationCentralized algorithms

A single on-line telephone bookCentralized data

A single server for all usersCentralized services

ExampleConcept


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Scaling Techniques (1)

1.4

The difference between letting:a) server orb) a client check forms as they are being filled


Scaling Techniques (2)

1.5

An example of dividing the DNS name space into zones.


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Summary

This Lecture

Introduction

Definition of Distributed Systems & Examples

Goals of Distributed System

Connecting Users and Resources, Transparency, Openness, Scalability

Next Lecture

Introduction

Multiprocessors

Distributed Operating Systems

Network Operating Systems

Middleware

distributed systems lecture 01

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