Chapter 2 Flashcards
What is a network application?
-The software packages that run in the applicationlayer.
What is an application architecture?
-The way in which the functions of the application layer software are spread among the clients and servers in the network.
What are the four general functions of the work done by an application program?
- Data storage
- data access logic
- application logic
- presentation logic
Describe data storage.
-programs require data to be stored and retrieved.
Describe data access logic.
-the processing required to access data such as database queries(SQL)
Describe application logic.
-business logic, simple or complex depending on the application
Presentation logic.
-the presentation of information to the user and the acceptance of the user’s commands.
What are the four fundamental application architectures?
- host-based architectures
- client-based architectures
- client-server architectures
- peer-to-peer architectures.
Describe host-based architecture.
-A server or large mainframe performs all four functions.
What are two problems with host based architectures?
- server must process all messages. Server can become overloaded.
- can’t prioritize, slow response time.
- lumpy upgrades
Describe client based architecture.
- client and server are both personal computers.
- client responsible for presentation, application, and data access logic.
- server responsible for data storage
What is a drawback to the client based architecture?
- all data on server must transfer to client for processing.
- can overload network circuits.
Describe client-server architectures.
- balance the processing between the client and the server by having both do some of the logic.
- client responsible for presentation logic
- server responsible for data access logic and data storage.
- application logic can reside on both or be split between both.
What is a strength and disadvantage of the client-server architecture?
-software and hardware from different vendors can be used but it’s hard to get them to work together and you need middleware.
What is middleware?
-software that sits between the application software on the client and the application software on the server.
What two things does middleware do?
- provides standard way of communicating that can translate between software from different vendors.
- manage message transfer from clients to servers
Describe a two-tier architecture?
-only uses one set of clients and one set of servers.
Describe a three-tier architecture
- uses three sets of computers.
- Client: presentation logic.
- server: application logic
- server: data access logic and data storage.
Describe a n-tier architecture
- client responsible for presentation logic.
- database server responsible for data access logic and data storage.
- application logic is spread across two or more different sets of servers.
What is an advantage of an n-tier architecture?
- separates processing that occurs to better balance the load on the different servers.
- is more scalable.
What are the disadvantages to an n-tier architecture?
- puts a greater load on the network.
- much more difficult to program and test software.
Describe a thin-client.
-little or no application on the client.
Describe a thick-client.
-places all or almost all of the application logic on the client.
Describe the distributed computing model.
-application systems use web browser as client software with java javascriptor AJAX downloaded as needed.
