4: Clients and Servers

Question 1

What is an IP address ?

Answer 1

A numerical label assigned to each device.

• IPv4: 4 integers, 32 bit
• IPv6: 6 ints, 128 bit

Function:

• Host identification
• Location addressing

Question 2

What is a port ?

Answer 2

An abstract gate for data to a computer.

Port 7: ECHO
Port 21: FTP
Port 80: HTTP

Question 3

What is a socket ?

Answer 3

A pair (IP address, port number) which is enough for a communication via TCP/IP.

Question 4

Given an example of a domain ?

Answer 4

machine1.csc.liv.ac.uk

Question 5

Give examples of top level domains ?

Answer 5

• com: commercial company
• edu: educational institution
• gov: government organisation
• org: other organisation

Question 6

Difference between client and server ?

Answer 6

• Client is a computer that requests some advice, server is a computer that provides this service.
• Can be hardware devices or software programs.
• Computer can be a client at a time, then a server at another.

Question 7

Give 4 advantages of the client-server model ?

Answer 7

• Openness: devices may run different OSs
• Scalability: many computers can be connected
• Specialisation: servers can be optimised for particular tasks
• Reliability: duplicate servers can readily replace faulty machines

Question 8

Types of servers ?

Answer 8

• File server: provides files for clients
• Database server: store large data collections
• Groupware server: organises the work of a group of people
• Web sever: stores components of web-pages and is accessed by a client’s web-browser
• Mail server: retrieves, stores, sends emails

Question 9

Architecture of client-server systems?

Answer 9

2 layers:

• Presentation and logic tier: manipulates and displays the data
• Data tier: holds the data for an application (eg relational DB)

Question 10

Middleware functionality examples?

Answer 10

• Detecting/correcting errors in transmission

- Interacting with lower-level protocols