3. WHAT IS DISTRIBUTED SYSTEMS ENGINEERING?
Distributed systems engineering is a field of software engineering that deals
with systems whose components are located on different computers within
the same network. A distributed system is, therefore, one that uses multiple
computers that coordinate their actions and communicate with one another to
achieve a common objective.
4. DISTRIBUTED SYSTEM
CHARACTERISTICS
Openness
• Use of equipment and software from different vendors
Scalability
• Increased throughput by adding new resources
Concurrency
• Concurrent processing to enhance performance
Transparency
• distributed system should be seen by both users and programmers as a single unit
5. CLIENT/SERVER
COMPUTING
Client/Server is a term used to describe a computing model for
the development of computerized systems. This model is based
on the distribution of functions between two types of
independent and autonomous processors: servers and clients.
This allows each layer to be distributed to a different computer.
Figure 18.6 illustrates this model, showing an application structured
into four layers:
6. CLIENT/SERVER
ARCHITECTURE
Clients
• The client is any computer process that requests services from the
server.
Servers
• The server is any computer process providing services to the clients.
Communication middleware
• It is any computer process(es) through which clients and servers
communicate.
7. ARCHITECTURAL PATTERNS FOR
DISTRIBUTED SYSTEMS
In this section, I discuss five architectural styles:
1. Master-slave architecture, which is used in real-time systems in which
guaran- teed interaction response times are required.
2. Two-tier client–server architecture, which is used for simple client–server
systems,
3. Multitier client–server architecture, which is used when there is a high
volume of transactions to be processed by the server.
4. Distributed component architecture, which is used when resources from
differ- ent systems and databases need to be combined
5. Peer-to-peer architecture, which is used when clients exchange locally
stored infor- mation and the role of the server is to introduce clients to
each other
8. SOFTWARE AS A SERVICE
Software as a service (or SaaS) is a way of delivering applications over the
Internet—as a service. Instead of installing and maintaining software, you simply
access it via the Internet, freeing yourself from complex software and hardware
management.
SaaS applications are sometimes called Web-based software, on-demand software, or
hosted software.
9. SAAS CHARACTERISTICS
Multitenant Architecture
• in which all users and applications share a single, common infrastructure and code base that is
centrally maintained.
Easy Customisation
• The ability for each user to easily customise applications to fit their business processes without
affecting the common infrastructure.
SaaS Trends
• Organisations are now developing SaaS integration platforms (or SIPs) for building additional SaaS
applications.
10. SAAS AND SOA
( SaaS ) is a way of providing functionality on a remote server with client access
through a web browser.
( SOA )is an approach to structuring a software system as a set of separate, state-
less services.
