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Distributed Systems Prof. Dr. Alexander Schill Dresden Technical University Computer Networks Dept. http://www.rn.inf.tu-dresden.de. Motivation and development tendencies. Desktop PC: multitasking networking direct manipulation, graphical interface high performance (CPU, transfer)

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Presentation Transcript
slide1

Distributed Systems

Prof. Dr. Alexander Schill

DresdenTechnical University

Computer Networks Dept.

http://www.rn.inf.tu-dresden.de

motivation and development tendencies
Motivation and development tendencies
  • Desktop PC:
  • multitasking
  • networking
  • direct manipulation, graphical interface
  • high performance (CPU, transfer)
  • large primary and secondary storage
  • Areas of application:
  • management / development (CASE – Computer Aided Software Engineering)
  • team working (CSCW – Computer Supported Collaborative Work)
  • group communication
  • process control (CIM – Computer Integrated Manufacturing)
sample topology
Sample topology

LAN

  • networked workstations, also organizationally integrated
  • super-proportionally increasing communication performance

WAN

L

V.A.N.

L

LAN (for instance high performance network)

Value added network

A

A

N

N

DistributedOS

Distributed DB

distributed system
Distributed System
  • physical computer nodes (processor + storage)
  • direct / indirect computer coupling
    • local networks (Ethernet (CSMA/CD), Token Ring, Token Bus)
    • high-performance networks (Gigabit Ethernet, ATM)
    • gateways / bridges
    • radio networks (GSM, UMTS)
  • transport-oriented comm. protocols (TCP/IP, UDP/IP, IPng)
  • communicating processes
    • complete logical connection
    • no complete physical connection (communication via inter-components)
  • system oriented resources (file system, threads, system programs)
  • distributed storage, decentralized, co-operative
  • distributed applications (area specific) on top of distributed systems
example distributed application
Example: distributed application

LAN

WAN

L

V.A.N.

L

LAN for instance high performance network)

Value added network

A

A

N

N

DistributedOS

Logical communication path

Process

Distributed DB

distribution purposes
Distribution: Purposes
  • data, function and load distribution
  • decentralization and co-operation
  • locality properties and efficiency
  • integration of partial applications
  • remote resource access
  • fault tolerance: reliability and availability
application example
Application example

Client

(for instance

Point of Sale)

Server

(for instance

account

server)

Server

(for instance

database)

Client

(for instance

Automated

Teller Machine)

Requirements:

- decentralized system structure

- Internet/Intranet-integration

- scalability

- security concepts

- transaction processing

- heterogeneity of systems

Client

(for instance

Home

Access)

network infrastructure examples
Network infrastructure: examples

ISDN / X.25Fast Ethernet / Token Ring

Client

(for instance

Point of Sale)

  • required bridging between
  • heterogeneous networks,
  • system platforms and
  • applications
  • Middleware

Fast Ethernet /Token Ring

Server

(for instance

account

server)

Server

(for instance

database)

ATM

Client

(for instance

Automated

Teller Machine)

X.25

Modem / ISDN / ADSLInternet-access

Client

(for instance

Home

Access)

n tier architectures
N-tier-architectures

Client

(for instance

Point of Sale)

Server

(for instance

account

server)

Server

(for instance

database)

Client

(for instance

Automated

Teller Machine)

Data management

Application logic

3-tier: three-level structure; preferable for

complex applications

2-tier: two-level structure (user-interface <->Host); simpler, but less flexible

Client

(for instance

Home

Access)

User interface,

if necessary

pre-processing

(thin client vs.fat client)

middleware and client server coordination

Client

(for instance

Point of Sale)

Server

(for instance account

server)

Middleware

(for instance

Java RMI, CORBA, .NET, SOAP)

Middleware

Transport-oriented

layers

(for instance TCP/IP, SNA)

Transport-oriented

layers

Phys. network

(for instance Fast Ethernet, Token Ring, ATM)

Phys. network

Middleware and Client/Server: coordination

Application

interaction

Object interaction

Def. of Middleware: “Infrastructure services for distributed applications for bridging of heterogeneity of different systems and networks”

middleware basic technologies
Middleware: Basic technologies

Java (Sun and others):

- programming language, applets

- Remote Method Invocation (RMI)

- Enterprise JavaBeans (EJB): Components

CORBA (Common Object Request Broker Architecture):

- object-oriented, language independent; relatively low-level

- standard of Object Management Group (OMG)

.NET / COM+ (Component Object Model):

- object-oriented, COM+ relatively proprietary, .NET more open

- development of Microsoft

Further approaches:

- MOM (Message Oriented Middleware)

- SOAP (Simple Object Access Protocol), Web Services

- transaction monitors, Application Servers

middleware general overview
Middleware: general overview

Application

Server /

Enterprise Appli-

cation Integration

Integrity

Usability

by

application

developer

Component-Frameworks

(CORBA, EnterpriseJavaBeans, .NET,

WebServices)

Transaction

monitors

Message Oriented

Middleware

Object TransactionMonitor

CORBA-/ RMI-/.NET/SOAP-Object-oriented

Basic comm.

Client/Server, Remote

Procedure Call (RPC)

(for instance

DCE - Distributed

Computing Environment)

Flexibility

system models
System models

Client/Server (Remote Procedure Call):

Client

Call

Result

Server

Offered

procedures

Control thread and data transfer

Separate address spaces

Object-oriented communication:

06

01

02

04

03

07

Computer 2

Computer 1

05

Computer 3

slide14

Document

Server

Document 1

Document 2

. . .

Document n

provide

document

(“Document 1”)

Client A

Copy

Document 1

generate

index

(“Document 1”)

Client B

Client C

provide

document

(“Document 3”)

Copy

Document 3

slide15

D1 = Server.provideDocument (“Document 1”)

D1.move (here)

D1.<operation>

Client-Object A

Document

Server

Document 1

Document 1

D2 = Server ...

D2.generate

Index ()

Document 2

Client-Object B

Document 2

. . .

Document n

Client-Object C

Document 3

D3 = Server.provideDocument (“Document 3”)

D3.<operation>

comparison of system models
Comparison of system models

higher transparency grade and improved influence on distribution

with object-oriented model

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