AQA A level Computer Science
Teaching and Learning Resources
Chapter 42 – The client-server model
TASK QUESTIONS (WITH ANSWERS)
1
What are the principles of the client server model? Give examples of where it might be used.
The client server model is a methodology for connecting computers together, usually over a
network where one computer provides access to resources for other computers that are
connected to it. It is used to provide a file server, web server, print server, database or
application server on a LAN.
2
What is thin- and thick-client computing?
Thick-client: in a network where resources, processing power and storage capacity are
distributed between the server and the client computers.
Thin-client: in a network where one computer contains the majority of resources, processing
power and storage capacity, which it distributes to other clients.
3
Give three advantages and three disadvantages of thin-client computing.
Advantages
•
Easy and cheaper to set up new clients as fewer resources are needed.
•
The server can be configured to distribute all the hardware and software resources
needed.
•
Hardware and software changes only need to be implemented on the server.
•
Easier for the network manager to control clients.
• Greater security as clients have fewer access rights.
Disadvantages
4
•
Clients are dependent on the server so if it goes down, all clients are affected.
•
Can slow down with heavy use.
•
May require greater bandwidth to cope with client request.
•
High-specification servers are expensive.
What is the purpose of an API?
It provides a common way for applications to work together across a network.
AQA A level Computer Science
© Hodder & Stoughton Limited 2015
AQA A level Computer Science
Teaching and Learning Resources
5
Explain how the websocket protocol creates a persistent connection between client and
server.
The client first sends a handshaking request to the server in order to establish the
connection. In response, the server creates a ‘full duplex’ connection on a single socket. This
allows simultaneous exchange of data in both directions, enabling the client and server to
communicate on an ongoing basis without the need to constantly request and respond to
data requests. Effectively, the websocket has created a dedicated line between the two
computers. This is routed through port 80, the dedicated HTTP port, meaning that it will
work in situations where non-web Internet connections have been blocked using a firewall.
6
Explain the relationship between CRUD, REST, SQL and HTTP.
These are all methods for interrogating data and there are corresponding commands in
each.
7
Explain where you might use JSON and XML and why you might choose to use one rather
than the other.
JSON and XML are two alternative methods for formatting data objects that are being
transferred across servers and web applications. See Table 42.1 on p358 of the Student
Book.
AQA A level Computer Science
© Hodder & Stoughton Limited 2015