SisTer-03-Challenges

8/7/2019 SisTer-03-Challenges

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Slide 1

INTRODUCTION TODISTRIBUTED SYSTEMS

DWS


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POKOK BAHASAN

Fitur Utama

Keuntungan Penggunaan Sistem Tersebar

Kelemahan Penggunaan Sistem Tersebar

Contoh Sistem Tersebar

Karakter Intranet, Internet dan Portable

Teknologi Web

Tantangan Penggunaan Sistem tersebar


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FITUR UTAMA

Geographical distribution of autonomous computers

Communication through cable/fibre/wireless/...

Connections

Distributed System Software


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ADVANTAGES

Interaction

Co-operation

Resource sharing

Communication

Economy

Speed

Inherent distribution

Reliability

Incremental growth


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BENEFIT

Reduced costs

Improved availability and performance


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Disadvantages of Distributed Systems

Software

Networking

Security


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Examples of Distributed Systems

Global Internet

Organizational Intranets behind router/firewall

Mobile Computing computers move

Ubiquitous Computing computers embedded everywhere

Issues: discovery of resources in different host environments

dynamic reconfiguration

limited connectivity

privacy and security guarantees to the user and the host environment


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A Typical Portion of the Internet


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A Typical Intranet


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Portable and Handheld Devices


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The Web

HTML, Hyper Text Markup Language

URL, Uniform Resource Locator http://servername[:port] [/pathname] [?arguments]

HTTP, HyperText Transfer Protocol

request-reply protocol (client-server) content types--MIME types, multipurpose internet mail extensions

one resource per request

simple access control (mostly public)


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Other Web Technologies

Web forms

CGI programs, common gateway interface, run on theserver

Applets, run on the client

RDF, resource description framework, vocabulary for meta-data

XML, extensible markup language, allow meta-datainformation to be included


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CHALLENGES

Heterogeneity

Openness

Security

Scalability

Failure handling

Concurrency of components

Transparency


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CHALLENGES

Heterogeneity Networks

Computer hardware

Operating systems

Programming languages

Need standard (middleware, protocol)


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CHALLENGES

Openness Ensures extensibility and maintainability of the system

Standard interfaces & their publication

Addition of new resources

RFC (Request for comments) specification for internet protocols

www. ietf.org

Benefits of ODS

Publishable Key interfaces (CORBA, MPI) Publishable communication mechanisms (Java RMI)

Construction

Heterogeneous components


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CHALLENGES

Security Confidentiality

Integrity

Availability

Example A doctor might request access to hospital patient data in electronic

commerce and banking, users send their credit card numbers across theinternet


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CHALLENGES

Scalability Controlling the cost of the physical resources

Does the system remain effective given the expected growth

Controlling the performance loss

www.amzon.com is more than one computer

Preventing the software resources running out

IP addressees: 32 bits to 128

Avoiding performance bottleneck Decentralization of data/information


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CHALLENGES

Failure handling

Detecting failure

Checksum can be used to detect corrupted data

System crash (impossible)

Tolerating failure

Exception handling (timeout when waiting for web source)

Recovery from failure Roll back


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CHALLENGES

Failure handling Redundancy

Redundant routes in network

Replication of name tables in multiple domain name servers

Database replication

Availability

Measure of the proportion of the time a server is available


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CHALLENGES

Transparency Concealing the heterogeneous and distributed nature of the system so that

it appears to the user like one system


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Challenges: Transparency

Failure transparency enables the concealment of faults, allowing users and application programs

to complete their tasks despite the failure of hardware or softwarecomponents.

Mobility transparency

allows the movement of resources and clients within a system withoutaffecting the operation of users or programs.

Performance transparency allows the system to be reconfigured to improve performance as loads

vary.

Scaling transparency allows the system and applications to expand in scale without change to

the system structure or the application algorithms.


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SisTer-03-Challenges

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