What is a Network?

A network is created when more than one device is connected together. A network can be a small collection of computers connected within a building (eg a school, business or home) or it can be a wide collection of computers connected around the world.

Networks can generally be put into two main types:

  • LAN – Local Area Network
  • WAN – Wide Area Network

A LAN is a collection of computers, servers, printers and other networked devices connected together in a network. This devices are connected together at the same physical location.

A WAN is a network of devices or other LANs connected over greater distance. The internet is an example of a WAN, or two offices connected together.


Local Area Network (LAN)


Wide Area Network (WAN)

Types of LAN

Within LANS the design topology can vary greatly depending on the type of network required. Each topology has a set of advantages and disadvantages. Opposite you will see some examples of network topology and the features of them.

Bus and Ring network topology’s were widely used however they were quite unreliable, with many points of failure. They have now been superseded in many cases by the use of a Star topology.

Even though Star topology’s are favored they do still have their failure points, switches tend to be the main interconnect between devices, if they go down, you lose the network.

Although not illustrated here a better solution than a Star is a Mesh. This created a physical connection between every device on the network eliminating points of failure. If a link goes down to a switch, it will find another route. The downside to this is both cost and complexity of installation.


In a bus network all the workstations, servers and printers are joined to one cable – ‘the bus’. At each end of the cable a terminator is fitted to stop signals reflecting back down the bus.


  • easy to install
  • cheap to install – it does not require much cabling


  • if the main cable fails or gets damaged, the whole network will fail
  • as more workstations are connected, the performance of the network will become slower because of data collisions
  • every workstation on the network ‘sees’ all of the data on the network, which can be a security risk

Bus Network Topology

Bus Network Topology


In a ring network, each device (eg workstation, server, printer) is connected in a ring so each one is connected to two other devices. Each data packet on the network travels in one direction. Each device receives each packet in turn until the destination device receives it.


  • this type of network can transfer data quickly (even if there are a large number of devices connected) as data only flows in one direction so there won’t be any data collisions


  • if the main cable fails or any device is faulty, then the whole network will fail – a serious problem in a company where communication is vital
Ring Network Topology


In a star network, each device on the network has its own cable that connects to a switch or hub. This is the most popular way of setting up a LAN. You may find a star network in a small network of five or six computers where speed is a priority.


  • very reliable – if one cable or device fails, then all the others will continue to work
  • high performing as no data collisions can occur


  • expensive to install as this type of network uses the most cable, and network cable is expensive
  • extra hardware is required – hubs or switches – which add to the cost
  • if a hub or switch fails, all the devices connected to it will have no network connection
Star Network Topology

Networking Equipment


A Hub is an Ethernet device that other network devices connect to. Servers, computers and printer can connect to hubs.

When data is sent out by a server to a hub the data is sent to all devices connected to it, even if it if not intended for them. This is because a hub is not a smart networking device, it literally passes data through without worrying about it.

Hubs are largely obsolete now, and have been replaced by switches.

Ethernet Hub


A switch is an Ethernet device similar in purpose and function as a hub.

The difference is that a switch knows about the connected devices. So builds up a list of addresses like a directory so when it received data intended for a one of its recipients it knows which port to send it out on.

It does this by using the MAC address of the connected devices, and builds and ARP list.


Client/Server and Peer-Peer each describes a particular networking architecture. Each architecture is more suitable for certain types of businesses.

Network Architecture

Client - Server Network

There’s a huge difference between Client/Server and Peer-Peer networks.

There are separate dedicated servers and clients in a client/server network. Through client workstations, users can access most files, which are generally stored on the server. The server will determine which users can access the files on the network.

There are an almost infinite variety of client/server networks, but all of them have a couple of things in common. For one thing, all have centralized security databases that control access to shared resources on servers.

The server contains a list of usernames and passwords. Users can’t log on to the network unless they supply valid usernames and passwords to the server. Once logged on, users may access only those resources that the network administrator allows them to access. Thus, client/server networks possess much more security than do peer-to-peer networks.

On most client/server networks shared resources reside on the server.

The primary downside to a client/server network is its cost. Servers can become very expensive. For example, you could pay over £800 for a copy of Windows Server software and five client licenses, and that price doesn’t even include the cost of the hardware, which must be more powerful than a standard workstation. Additionally, client/server networks require an employee to manage them.

Peer - Peer

A peer-to-peer network has no central server. Each workstation on the network shares its files equally with the others. There’s no central storage or authentication of users.

They are inexpensive to set up, and are appropriate only for very small businesses or for home use. A peer-to-peer network can support about ten clients (workstations) before it begins to suffer from some serious performance and management problems

The concept behind peer-to-peer networking is to share files and printers as inexpensively as possible; therefore, there’s no main server on the network. Instead, each client functions both as a client and as a server simultaneously. Since users are allowed to control access to the resources on their own computers, however, security becomes very risky in a peer-to-peer environment. There’s no central security or any way to control who shares what. Users are free to create any network share points on their computers. The only security on a peer-to-peer network is at the share level. When users create network shares, they may implement no security, which means that anyone can have full access to the share, or they may assign a password to the share. Depending on which networking platform you use, a user may be able to assign one password to a share for read-only access and another password for full control over the share.

Although this arrangement may sound somewhat secure, it isn’t. The computer that contains the shared resources doesn’t check on who’s trying to access those resources. Any user can access them as long as the user knows the password. If someone happens to write down a password, anyone who finds that password can access the share.

Network Protocols

A computer network is similar to a road network in that it has rules (protocols) that you need to follow and only a certain number of vehicles (data) can get through at a time (bandwidth). If too many vehicles try to go down the same road you get congestion (reduced bandwidth).

When two devices send messages to each other it is called handshaking – the client requests access, the server grants it, and the protocols are agreed. Once the handshaking process is complete, the data transfer can begin.

Protocols establish how two computers send and receive a message. Data packets travel between source and destination from one router to the next.

The process of exchanging data packets is known as packet switching. Click Here to read more on Packet Switching.

TCP/IP (transmission control protocol/internet protocol)

TCP/IP (also known as the internet protocol suite) is the set of protocols used over the internet. It organises how data packets are communicated and makes sure packets have the following information:

  • source – which computer the message came from
  • destination – where the message should go
  • packet sequence – the order the message data should be re-assembled
  • data – the data of the message
  • error check – the check to see that the message has been sent correctly

Within the TCP/IP protocol stack, there are many key protocols, that designate the type of packets, and how they will be transferred and represented.

  • FTP – File Transfer Protocol – Handles the transfer of files over a network, used to upload files for website
  • SMTP – Simple Mail Transfer Protocol – Handles the transfer of email messages
  • HTTP – Hypertext Transfer Protocol – Handles the transfer and display of websites in a browser

IP Addressing

An IP address is an address used in order to uniquely identify a device on an IP network. The address is made up of 32 binary bits, which can be divisible into a network portion and host portion with the help of a subnet mask. The 32 binary bits are broken into four octets (1 octet = 8 bits). Each octet is converted to decimal and separated by a period (dot). For this reason, an IP address is said to be expressed in dotted decimal format (for example, The value in each octet ranges from 0 to 255 decimal, or 00000000 – 11111111 binary.

Click Here for more info on IP addressing