System Models
Dr Simon Blake
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Guidelines and tips
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Distributed Information Systems Lecture 3 - System Models, Lecture notes of Computers and Information technologies
Summary about System Models, Architectural models, Fundamental models, Systems need to be designed,System models, Major concerns.
Typology: Lecture notes
2010/2011
1 / 34
This page cannot be seen from the preview
Don't miss anything!
Related documents
Partial preview of the text
Download Distributed Information Systems Lecture 3 - System Models and more Lecture notes Computers and Information technologies in PDF only on Docsity!
System Models
Dr Simon Blake
Topics for this lecture
- Architectural models
- Layers• System Architectures• Interfaces and objects• Design requirements
- Fundamental models
- Interaction• Failure• Security
- Fundamental models
- Layers• System Architectures• Interfaces and objects• Design requirements
System models
-^
Architectural models^ –
The placement of parts in the system, i.e. Client-server, peer-peer
-^
Fundamental models^ –
No global time
-^
Communication achieved by message passing
-^
Message delays, communication failures, security
-^
Three types of fundamental model
-^
Interaction
-^
Performance and timing
-^
Failure model
-^
Specify failures and defines correct process
-^
Security model
-^
Securing communication and processes
Architectural models
- Major concerns:
- Manageable, reliable, adaptable and cost-
effective
- One aim is to simplify design– Another is the placement of components in a
useful manner
- While considering the interrelationship
between components
Software layers
Applications, services
Middleware Operating systems
Computer and network hardware
Applications, services
MiddlewareOperating systems
Computer and network hardware
Two, abstract ideas of layers that imply the same meaning
Platform
Software layers and messages
Messaging is required between the layers
Applications, services
Middleware Operating systems
Computer and network hardware
messagesmessages messages
Middleware layers
Applications, services
Middleware Operating systems
Computer and network hardware
Platform
Request(s)Request(s)
Response(s)Response(s)
The Middleware layer acts as a mediator that brokers the request fromapplications, services
System Architectures
Client Client Client
Server
Server
invocation invocation invocation
invocation
result result
result
result
= message
= process
= computer
Proxy server
Client Client
Proxy Server
request
reply
Web Server
Web Server
request
reply
Peer processes
ApplicationCoordinator
ApplicationCoordinator
ApplicationCoordinator
Other client server models
•^
Networked computers^ – Download OS and Applications from a server– Use low spec clients– Increase network traffic
-^
Mobile code^ – Download from a sever code which is run by clients– This code might then require server communication– A code way of distributing applications
Spontaneous networks
Internet
gateway
PDA
service
Musicservice
Discoveryservice
Alarm Camera
Guest'sdevices
Laptop
TV/PC
Hotel wirelessnetwork
Design requirements
- Performance requirements
- Responsiveness
- We want responsive systems• It is affected by network latency, traffic, server
- Responsiveness
queues, the number of software layers
- Throughput
- Determines the capacity of the DIS?
- Load balancing
- Can we share work to improve performance• i.e. the use of replicated services
- Load balancing
- Determines the capacity of the DIS?
Design requirements
- Quality of service requirements
- Requires a reasonable or defined level of
performance levels
- Security and reliability
- Are services available?– Can they deliver the services they claim to?– Is the system secure?