Networks Yr 11 Summary

Network Introduction

What is a network?

A computer network is two or more computing devices (such as a computer) connected together in order to share resources and exchange information.

Network enabled devices could be:

Network servers

Personal computers

Tablets

Smart phones

E-readers

Smart televisions

Printers

LANs and WANs

There are two types of networks that you need to understand,

Local Area Networks (LANs) and Wide Area Networks (WANs).

Multiple Choice

What is the correct definition of a network?

• A computer network is two or more computing devices (such as a computer) connected together

• A computer network is when lots of servers are connected together

• A computer network are computers based in the cloud

Multiple Select

What are the 2 main types of network?

• WAN and MAN

• MAN and TAN

• LAN and WAN

LAN - Local Area Network

• A Local Area Network is one that has two or more network-enabled devices connected within a fairly close geographical area

• For example the LAN may be located within a single building such as a home or business office or it may cover a few nearby buildings as well, such as an University campus, hospital, library or school.

• The diagram below shows a typical business LAN with a network server connected to a number of computers. A wireless access point is also connected to the network so that Wi-Fi devices such as laptops can connect to the network.

LAN

This network has a central server connected to a switch. A number of workstations and wi-fi enabled devices are connected.

Computers and devices can be connected by physical Ethernet cables, which are usually owned by the organisation. They can also be connected wirelessly by using Wi-Fi connections.

To log onto a LAN, you usually need a user name and password, just like you do at school. The user name identifies you to the file server so that it can 'serve' you the correct files. The password ensures that the user name really does belong to you.

Multiple Select

What are the 2 key features of a LAN? (Choose 2)

• It is in one building

• A LAN is spread over a large area

• It is in a fairly close geographical area

• The connection medium is owned by the organisation

LANs at home

Many homes now have LANs where many devices other than workstations can connect together in order to share data. Here is an example of what a LAN within a home might look like:

Advantages of LANs

• A LAN usually offers the following benefits :

  A user can log on from any workstation and still access all of their files.

• Peripherals such as printers and photocopiers can be shared between many users, thus reducing costs

• Resources and files can be shared by users, this means that they can collaborate on a project.

• Backups of files and documents can be done centrally rather than needing to do it from each machine

• When software needs to be installed it can be done centrally rather than having to go to each individual workstation.

• An anti-virus and malware check can be carried out from the server to all workstations.

• Data can be transmitted very quickly between networked computers A LAN at home allows many devices to connect to one another, such as a smart TV or a media server

WAN - Wide Area Network

A wide area network (WAN) connects two or more local area networks (LAN) that are in larger geographical locations.

WANs

For example, a company might have offices in London and also New York, but they want to share a common work area so they can collaborate. In this case the LAN in London is connected to the LAN in New York by a Wide Area Network.

A WAN can also connect offices that are a bit closer together, such as estate agent offices in different towns. In this case a 'leased line' from a telecom company can be used.

A company normally hires the WAN from a major telecom company because it is so expensive and complicated to set up and maintain. In a WAN the organisation doesn't normally own the connection methods.

The WAN involves long distance communications and this can be achieved using

Fibre optic lines, including laying undersea cables

Satellite communication links

Leased telephone lines

Microwave links

The largest WAN of all is of course the internet. No single organisation owns the internet itself.

Multiple Choice

What does WAN stand for?

• World Arena Network

• Wide Arena Network

• Wide Area Network

Multiple Select

What are the 2 key features of a WAN? (Choose 2)

• It is in one building

• It is spread over a large area

• It is in a fairly close geographical area

• The connection medium is not owned by the organisation

Client/Server

• A client/server network has a server that is in control of the other clients on the network.

• This is the most common structure

Peer to Peer

• A peer to peer network has no computer in charge. All the computers are equal.

• This is only suitable for small networks, such as home networks.

Advantages of Client/Server Network

• All files can be stored centrally / accessed from any machine

• All back ups can be done centrally

• Upgrading software can be be done centrally

Multiple Choice

Which type of network is controlled by a central server?

• Peer to peer

• client/server

Multiple Choice

Which type of network has the advantage that files can be stored centrally?

• Peer to peer

• client/server

Multiple Choice

Which type of network has the advantage that software can be installed centrally?

• Peer to peer

• client/server

Multiple Choice

Which type of network has the advantage that backups can be done centrally?

• Peer to peer

• client/server

Wired v Wireless

• Devices on a network need to be joined together. They are connected using a transmission medium.

• This could be wired or wireless

Wired networks

• There are different ways of connecting a wired network.

• The most common type of cable is an Ethernet cable.

• It has quite a fast transmission speed

Wireless Networks

• Wireless networks are usually connected using Wi-Fi

• Wi-Fi is more likely to be affected by interference

• Wi-fi has can travel shorter range before data is lost

Wireless Networks

• Adding a wireless network will probably increase the number of devices trying to access the network, eg mobile phones, whcih will reduce the available bandwidth for all users

Multiple Choice

Which type of network connection is a wired connection?

• Ethernet

• Wi-Fi

Multiple Choice

Which type of network connection is a wireless connection?

• Ethernet

• Wi-Fi

Multiple Choice

Which type of network connection can transmit data at faster speeds?

• Ethernet

• Wi-Fi

Multiple Choice

Which type of network connection is more likely to suffer from interference?

• Ethernet

• Wi-Fi

Multiple Choice

Which type of network connection has a shorter range before data will be lost?

• Ethernet

• Wi-Fi

Network Performance

• There are several factors that can affect the performance of the network:

• Bandwidth - how much data can be transferred over a connection in a given time. It is measured in bits per second, eg Kbps or Mpbs

• Number of users - the more people that have to share the bandwidth, the less there is for each one

• Interference - eg walls or electricity

• Distance - the longer the distance the data has to travel, the more chance that data will be corrupted

• Server specification - a slower server will slow down the whole network

• Using a hub instead of a switch

Multiple Choice

Which of the following would improve the performance of the network?

• Increasing bandwidth

• Adding more users

Multiple Choice

Which of the following would reduce the performance of the network?

• Increasing bandwidth

• Adding more users

Topologies

• A network topology describes how the devices are connected together logically.

• There are 2 main types: Mesh and STAR

Advantages of the STAR Network

• It is easy to add a new device on to the network

• Management of the network can be done centrally

• There will be fewer data collisions

• It is more secure as the data is only sent to the intended computer

• If a computer fails the rest of the network is unaffected.

Email Protocols

• A protocol is a set of rules

• They ensure that all devices are communicating in the same way

• SMTP - Simple Mail Transfer Protocol is used to send emails

• POP - Post office Protocol is used to receive emails. Once downloaded they are deleted off the server and cannot be accessed form another device.

• IMAP - Internet message Access Protocol is an alternative for receiving emails. It keeps a copy of the email on the server so it can be accessed from different devices.