Jaringan Informasi

Pengantar Sistem Terdistribusi

olehIr. Risanuri Hidayat, M.Sc.

Motivation

● Share resources● Personalise environments● Location independence● People & information are distributed● Performance & cost● Modularity & expandability● Availability & reliability● Scalability

Goal

● Performance● Reliability● Scalability● Consistency● Security

IssuesDesign● Naming● Communication● Software structure

– well-defined interfaces – abstractions/layering & support

services● Scale● Partial failure

– detection, masking & tolerance– recovery

Security● Centralized systems:

– can rely on physical security– Users understand what trust to

assign to the system– System administrators are

responsible● Distributed systems:

– None of the above applies !– Hard to know what is being trusted

or what can be trusted

Transparency● Access● Location● Concurrency● Replication● Failure● Mobility● Performance

– Reconfiguration– Scale

DefinitionColouris● System of networked computers that

– communicate and coordinate their actions only by passing messages● concurrent execution of programs● no global clock ● components fail independently of one another

Tanenbaum● A collection of independent computers that appear to the users as a single

coherent system– autonomous computers

● connected by a network– software specifically designed to provide an integrated computing facility

Definition

Lamport● “You know you have a distributed system

when the crash of a computer you’ve never heard of stops you from getting any work done.”– inter-dependencies – shared state– independent failure of components

● partial failures

Clock dan Sinkronisasi

Clock dan Sinkronisasi

Server Cluster

Server Cluster

Server Cluster

Interaksi Peer to peer

Coordination

Application

code

Coordination

Application

code

Coordination

Application

code

Mobile Code Example: Appletsa) client request results in the downloading of applet code

Web server

ClientWeb serverApplet

Applet code

Client

b) client interacts with the applet

Thin Client-Compute Server

ThinClient

ApplicationProcess

Network computer or PCCompute server

network

IPC

proc es s p proces s q

C ommunication channel

send

O utgoing mes s age buffer Incoming mes s age buffer

receivem

Interaksi Client-Server

• Remote Procedure Call

Interaksi C-S

● Multi-tier

Interaksi C-S

Interaksi C-S

● Asinkron RPC

Web

● TCP/IP● DNS● HTTP● HTML● Caching● Server clusters

Layering

Hardware

Host-to-Host Connectivity

Request-ReplyChannel

Message StreamChannel

Application Programs

Protocol Graph

OSI Network Architecture

Application

Data Link

Network

Transport

Session

Presentation

Physical Physical

Network

Data Link

Physical

Network

Data Link

Physical -> raw bitsData Link -> framesNetwork -> packets

Transport -> process-to-process

Application

Data Link

Network

Transport

Session

Presentation

Physical

Internet Architecture

Network

IPTCPUDP

Application

Transport

Datagrams

Messages (UDP)Streams (TCP)

Encapsulation

App

Data

RRP Data

HHP

RRP

App

Data

RRP Data

HHP

RRP

RRP DataHHP