Distributed Systems

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Distributed Systems

• ... Sistemi Distribuiti ...
• ... Per la laurea specialistica
• in Ingegneria Informatica ...
• II anno

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Distributed Systems

• a.y. 2006/2007
• Instructor Carlo Ferrari
• Department of Information Engineering,
• The University of Padova

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Distributed Systems (lecture 1 - 2/10/06)

• Course introduction
• Introduction to Distributed Systems

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Sistemi Distribuiti

• Obiettivi formativi
• Presentare in forma sistematica le problematiche
  fondamentali riguardanti il progetto di sistemi
  distribuiti con particolare riferimento alle
  questioni relative
• alla gestione della loro eterogeneità,
• alla scalabilità,
• alla condivisione di risorse,
• alla sicurezza,
• alla tolleranza ai guasti,
• al controllo della concorrenza

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Sistemi Distribuiti

• Modelli e architetture
• Oggetti distribuiti e invocazione remota
• Affidabilità e fault tolerance
• La replica dei dati
• Transazioni distribuite
• e inoltre ...
• Modelli e strumenti per la programmazione

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Sistemi Distribuiti

• Ambiti applicativi ...
• Distributed Supercomputing
• On-demand Computing
• Data-Intensive Computing
• Collaborative Computing
• Multimedia

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Sistemi Distribuiti

• George Coulouris, Jean Dollimore, Tim Kindberg,
• Distributed Systems concepts and design,
  fourth edition,
• Addison-Wesley, 2005
• Third edition, 2001 ... is still OK (at 85)

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Sistemi Distribuiti

• A.S. Tanenbaum, M. Van Steen, Distributed
  Systems Principles and Paradigm, Prentice-Hall,
  2002
• M.L. Liu, Distributed Computing, principles and
  applications, Pearson 2004
• J. Graba, An introduction to Network Programming
  with Java, Addison-Wesley, 2003

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Sistemi Distribuiti

• 7 CFU, 54 ore complessive in 9 settimane
• Lezioni
• Lunedì, 10.30-12.00 Aula Le
• Martedì, 10.30-12.00, Aula Le
• Mercoledì, 10.30-12.00, Aula Le
• Ricevimento studenti
• Martedì, 14.30-16.30, DEI-G stanza 313
• per appuntamento
• carlo_at_dei.unipd.it, 049-827.7729,

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Sistemi Distribuiti

• Prerequisiti
• ................................. TUTTO
  ..................................
• Reti di calcolatori,
• Basi di Dati,
• Sistemi Operativi

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• Basi di Dati
• Sistemi Operativi 1
• ...ma anche
• Intelligenza Artificiale
• Informatica Musicale

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Sistemi Distribuiti

• Una piccola formalità
• Iscrizione OBBLIGATORIA al corso da effettuarsi
  tramite bacheche elettroniche, ovvero
  sis.dei.unipd.it) seguire il link Informazioni
  delle strutture-Dipartimento di Ingegneria
  dellInformazione-Liste di iscrizione ad appelli
  o corsi-Iscrizione a un appello o corso e poi
  selezionare dalla lista Sistemi Distribuiti
• Iscrizioni aperte dal 2 ottobre al 6 ottobre

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Sistemi Distribuiti

• Modalità desame, aspetti generali
• 5 appelli nel corso della.a.
• 2 appelli, al termine del primo trimestre
  (trimestre di erogazione del corso-sessione
  autunnale)
• Sicuramente 1 appello nella sessione di recupero
  (settembre)
• Gli altri 2 appelli sono previsti in due diversi
  periodi scelti tra la sessione primaverile, la
  sessione estiva e la sessione di recupero.
• nessun vincolo alla partecipazione
• Lesame si conclude con una discussione orale

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Sistemi Distribuiti

• Modalità desame aspetti particolari (ancora in
  via di definizione)
• Prova scritta
• Elaborato/progetto
• Presentazioni
• (dipende dal numero e dalla tipologia di studenti
  iscritti ...) ma comunque ci saranno dei
  cambiamenti rispetto allo scorso anno !

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Sistemi Distribuiti

• Avvisi

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Sistemi Distribuiti

• Sito del corso
• ............ ??? .................

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Sistemi Distribuiti

• Sito collegato al libro di riferimento
• www.cdk4.net oppure
• www.pearsoned.co.uk/coulouris

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Sistemi Distribuiti

• Attività di laboratorio
• ... Non prevista .... ? .... forse ....

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Sistemi Distribuiti

• Tesi di laurea specialistica in ingegneria
  informatica
• 20 crediti .... 29 crediti .... 35 crediti
• 9 crediti .... 6 crediti liberi ... 0 crediti
• 6 crediti liberi

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Sistemi Distributi

• Laboratorio di Sistemi Distribuiti
• Laboratorio di Bioinformatica Strutturale
• ... ma anche
• Laboratori di Robotica, Telecomunicazioni,
  Sistemi in tempo reale, Musica al calcolatore,
  Basi di Dati, Sistemi Informatici, ....

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Sistemi Distributi

• Attenzione alle tempistiche ...
• 20 crediti ... 4 mesi/uomo
• 29 crediti ... 6 mesi/uomo
• 35 crediti ... 7 mesi/uomo

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• Bioinformatica
• Sistemi Distribuiti
• Grid Computing
• Agents
• Biometrics

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Distributed Systems
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Our goal ...

• Explain the characteristics of networked
  computers and introduce/review the principles
  involved in the design of distributed systems.

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• Overview the fundamental problems and the current
  techniques for their solution.
• Foresee new research directions and new
  solutions.

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Why Distributed Systems?

• Because we want to share resources

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• in spite of geographical distribution of
  autonomous computers and/or their mobility
• thanks to communication through
  cable/fibre/wireless/... connections

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• Advantages
• improved capabilities, availability and
  performance
• reduced costs
• Important questions
• interaction, co-operation and sharing

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(No Transcript)
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Distributed Systems Main Issues

• ?

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• Networked computer can be spatially
• separated by any distance ...
• Concurrency
• No global clock
• Independent failures

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• Distributed Computing
• VS.
• Parallel Computing

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Introduction

• Definition of Distributed Systems
• Examples
• Internet
• intranets
• mobile and ubiquitous computing
• The World-Wide Web
• Characteristics
• Challenges

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Definitions

• A Distributed System is a collection of
  autonomous computers interconnected by a computer
  network and equipped with distributed system
  software to form an integrated computing
  facility. (system oriented)

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• A Distributed System is a collection of
  independent computers that appears to its users
  as a single coherent system. (user oriented)

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more definitions ...

• A Distributed System is a collection of
  independent computers interconnected via a
  network, that are capable of collaborating on a
  task (task oriented)

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• A Distributed System is a collection of
  individual computing devices that can communicate
  each other (infrastructure oriented)

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• Processes
• execute concurrently
• interact in order to co-operate to achieve a
  common goal
• co-ordinate their activities and exchange
  information by means of messages transferred over
  a communication network

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Typical examples

• Internet
• global network of interconnected computers
  which communicate through IP protocols
• Intranet
• a separately administered network with a
  boundary that allows to enforce local security
  policies
• Mobile and ubiquitous (pervasive) computing
• laptops, PDAs, mobile phones, printers, home
  devices, ..
• The World-Wide Web
• system for publishing and accessing resources
  and services across the Internet

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Internet
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Characteristics of Internet

• very large and heterogeneous
• open-ended
• connects intranets (via backbones) with home
  users (via modems, ISPs)
• enables email, file transfer, multimedia
  communications, WWW,...

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a typical Intranet
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Characteristics of intranets

• several LANs linked by backbones
• often connected to Internet via router
• in/out communications protected by firewall
• enables information flow within organisation
• (electronic data, documents, )
• provides services (email, file, print servers,
  ...)

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Portable and handheld devices
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Mobile ubiquitous computing

• Wireless LANs (WLANs)
• connectivity for portable devices (laptops,
  PDAs, mobile phones, video/dig. cameras, )
• WAP (Wireless Applications Protocol)
• Home intranet
• devices embedded in home appliances (hi-fi,
  washing machines, )
• universal remote control communication

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• SERVICE
• SERVER
• CLIENT
• REMOTE INVOCATION

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Web servers and web browsers
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World Wide Web

• publishing and accessing resource and services
  world-wide across the Internet
• client-server architecture
• open system
• can be extended, re-implemented, ...
• (technologies HTML, URL, HTTP)

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Client-server

• A service a part of a (computer) systems that
  manages a collection of related resources and
  presents their functionality to users and
  applications
• It reflects the physical encapsulation of
  resources in Distributed Systems

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Client-server

• Server a running program (process) that accepts
  requests from programs running on other computer
  to performe a service and respond appropriately
• Client the requesting process
• Remote invocation the whole process of sending a
  request and receiving a response

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but

• Dangling links
• Lost in hyperspace
• Search engines
• Metadata and web resources
• XML and data portability
• Scaling
• User interface

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Challenges posed by DSs

• Due to
• complexity
• size
• changing technologies
• societys dependence