2 layouts depending on the nodes and their purpose

• Client – Server  

• Peer to Peer

Client – Server 

• Setting up one particular node to be more important than the other nodes

• This most important node is called the server as it usually holds the programs and sometimes the data of the other nodes (called clients)

• Flat client and thin clients

Peer to Peer

• Each node on the network has equal responsibility

• This means that nodes share their resources (printers, hard disk etc) with the other nodes

A bit more detail

Client – Server

As the name client-server suggests, there are two different types of computers present in a network, namely servers and clients.

The Server provides particular processing resources and services for each client machine.  For example, webservers retrieve and transmit web pages, and database servers retrieve and transmit records.

The Client machines, which are commonly personal computers, also perform their own local processing. For example, web browsers, email clients, and database applications. 

Each server provides processing services to multiple clients.

This is what we are most used to at places like school….and we are used to Fat clients, not only because of the obesity issue currently facing Australia, but because this model has a number of benefits. 

Thin Client

This is also known as a slim or lean client or a graphical terminal and even a dumb terminal. Basically the client computer does hardly any processing of data. Instead it relies on a server which does all the processing for it. As you can imagine there are various degrees of thin clients. If you heard of the old mainframe computers, they were usually found in large institutions such as hospitals and universities. They consisted of a really big computer that had sometimes hundreds of thin clients attached to it. The programs, drivers and processing was all done by the mainframe (it acted as the server) and the thin clients were used to simply access the programs and computing power of the mainframe server. 

Today in some libraries there are terminals that only allow interrogation of the library catalogue – these are usually examples of thin clients. Also, some systems such as Citrix and Terminal Services rely on a centrally stored set of applications that can be run remotely from a client machine. 

You could think of a thin client as a screen, keyboard, mouse and little else apart from something to run the network card.

Advantages of thin clients:

• Cheap to acquire

• Security can be organised centrally

• Alterations to software etc is easy to do centrally

• Single point of failure…could also be a disadvantage

• Cost of software can be cheaper through licencing

Disadvantages

• Slow as processing is done remotely

• No ability for stand alone functionality

• May not be able to successfully connect and operate peripheral devices

Fat Client

This is what we are most used to. Think of a computer in the classroom. It relies on another computer to get internet access – a web server, it relies on another computer to get access to student directories – a file server, it relies on another computer in order to print – print server. 

Fat clients are also known as thick clients, heavy or rich clients. They are able to do a lot of processing themselves (if not all) and can usually operate quite effectively in stand alone mode. They have a full operating system and only rely on servers to fulfil quite specific functions such as those described above, and also other server functionality such as mail, database, name, ftp, proxy and so on.

Advantages 

• Can work independently – more flexible + work offline

• Increased speed of network

• Very specific security can be enacted

• Multimedia applications work much faster

• Lower server requirements meaning higher server capacity (speed)

Disadvantages

• More expensive to set up

• Can mean much more upkeep / maintenance 

• Can create more security issues

Peer to peer network

You may have a peer to peer (p2p) network at home where computers can share files and resources such as printers, without any one machine being more important or in charge. Each machine in the p2p network is called a node and the processing and files are distributed among the nodes. 

You may be familiar with Napster, Limewire or the more current Vuze systems (incorporating torrents and sites like torrentreactor or piratebay ) which all use / d peer to peer networking architecture to distribute software, music, videos and computer games freely among peer to peer nodes. 

Advantages

• No single point of failure

• Each node brings its own processing power, storage space and files which makes the system capacity increase

• No need for a system administrator

Disadvantages

• Social and ethical issues – copyright, harmful material.

• Security vulnerability

• Administrator super rights – files can be removed on a whim