chapter 2 slides.ppt

Slides for Chapter 2: Architectural Models

From Coulouris, Dollimore and Kindberg

Distributed Systems: Concepts and Design

Edition 3, © Addison-Wesley 2001

Instructor’s Guide for Coulouris, Dollimore and Kindberg Distributed Systems: Concepts and Design Edn. 3

© Addison-Wesley Publishers 2000

Figure 2.1Software and hardware service layers in distributed systems

Applications, services

Computer and network hardware

Platform

Operating system

Middleware



Figure 2.2Clients invoke individual servers

Server

Client

Client

invocation

result

Serverinvocation

result

Process:Key:

Computer:



Figure 2.3A service provided by multiple servers

Server

Server

Server

Service

Client

Client



Figure 2.4Web proxy server

Client

Proxy

Web

server

Web

server

serverClient



Figure 2.5A distributed application based on peer processes

Coordination

Application

code

Coordination

Application

code

Coordination

Application

code



Figure 2.6Web applets

a) client request results in the downloading of applet code

Web server

ClientWeb serverApplet

Applet code

Client

b) client interacts with the applet



Figure 2.7Thin clients and compute servers

ThinClient

ApplicationProcess

Network computer or PCCompute server

network



Figure 2.8Spontaneous networking in a hotel

Internet

gateway

PDA

service

Music service

serviceDiscovery

Alarm

Camera

Guestsdevices

LaptopTV/PC

Hotel wirelessnetwork



Figure 2.9Real-time ordering of events

send

receive

send

receive

m1 m2

2

1

3

4X

Y

Z

Physical time

Am3

receive receive

send

receive receive receivet1 t2 t3

receive

receive

m2

m1



Figure 2.10Processes and channels

process p process q

Communication channel

send

Outgoing message buffer Incoming message buffer

receivem



Figure 2.11Omission and arbitrary failures

Class of failure Affects DescriptionFail-stop Process Process halts and remains halted. Other processes may

detect this state.Crash Process Process halts and remains halted. Other processes may

not be able to detect this state.Omission Channel A message inserted in an outgoing message buffer never

arrives at the other end’s incoming message buffer.Send-omission Process A process completes a send, but the message is not put

in its outgoing message buffer.Receive-omission Process A message is put in a process’s incoming message

buffer, but that process does not receive it.Arbitrary(Byzantine)

Process orchannel

Process/channel exhibits arbitrary behaviour: it maysend/transmit arbitrary messages at arbitrary times,commit omissions; a process may stop or take anincorrect step.



Figure 2.12Timing failures

Class of Failure Affects DescriptionClock Process Process’s local clock exceeds the bounds on its

rate of drift from real time.Performance Process Process exceeds the bounds on the interval

between two steps.Performance Channel A message’s transmission takes longer than the

stated bound.



Figure 2.13Objects and principals

Network

invocation

resultClient

Server

Principal (user) Principal (server)

ObjectAccess rights



Figure 2.14The enemy

Communication channel

Copy of m

Process p Process qm

The enemym’



Figure 2.15Secure channels

Principal A

Secure channelProcess p Process q

Principal B

chapter 2 slides.ppt

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